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Endorphins (endogenous morphine) are endogenous opioid neuro-peptides and peptide hormones in humans and animals. They are produced by the central nervous system and the pituitary gland. The term "endorphins" consists of two parts: endo-and-orphin; intended to mean "a morphine-like substance originating from within the body". The principal function of endorphins is to inhibit the communication of pain signals and produce a feeling of euphoria very similar to that produced by other opioids β-endorphins are the best in pain relief and its production is hereditary, due to this, its production level varies from animal to animal. Endorphins are naturally produced in response to pain but their production can also be triggered by various activities This review aims to focus on how higher concentrations of β-endorphins decreases stress and maintain homeostasis resulting in pain management and are involved in natural reward circuits such as feeding, drinking, sex and maternal behavior.
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International Journal of Chemical Studies 2019; 7(3): 323-332
P-ISSN: 23498528
E-ISSN: 23214902
IJCS 2019; 7(3): 323-332
© 2019 IJCS
Received: 25-03-2019
Accepted: 30-04-2019
Anand Jain
Department of Veterinary
Physiology and Biochemistry,
Jabalpur, Madhya Pradesh,
India
Aditya Mishra
Department of Veterinary
Physiology and Biochemistry,
Jabalpur, Madhya Pradesh,
India
Jyotsana Shakkarpude
Department of Veterinary
Physiology and Biochemistry,
Jabalpur, Madhya Pradesh,
India
Preeti Lakhani
Department of Veterinary
Physiology and Biochemistry,
Jabalpur, Madhya Pradesh,
India
Correspondence
Anand Jain
Department of Veterinary
Physiology and Biochemistry,
Jabalpur, Madhya Pradesh,
India
Beta endorphins: The natural opioids
Anand Jain, Aditya Mishra, Jyotsana Shakkarpude and Preeti Lakhani
Abstract
Endorphins (endogenous morphine) are endogenous opioid neuro-peptides and peptide hormones in
humans and animals. They are produced by the central nervous system and the pituitary gland. The term
"endorphins" consists of two parts: endo- and -orphin; intended to mean "a morphine-like substance
originating from within the body". The principal function of endorphins is to inhibit the communication
of pain signals and produce a feeling of euphoria very similar to that produced by other opioids β-
endorphins are the best in pain relief and its production is hereditary, due to this, its production level
varies from animal to animal. Endorphins are naturally produced in response to pain but their production
can also be triggered by various activities This review aims to focus on how higher concentrations of β-
endorphins decreases stress and maintain homeostasis resulting in pain management and are involved in
natural reward circuits such as feeding, drinking, sex and maternal behavior.
Keywords: Opioids, analgesic, antistressor, immunomodulator and anti-inflammatory agent
Introduction
Our body produces hundreds of chemicals to make sure the body works properly. Of these
many hormones are one of the most important one because these hormones must be present in
the exact amount in the blood, as hypo-secretion or hyper-secretion of hormones may cause
diseases and abnormalities. There are various hormones that some people even don’t know.
Without hormones the body will not work properly or will not do its functions normally. There
are hormones which act on target organs and not other organs. Even the release of these
hormones is based on the typical stimuli by typical organ or any parameter. But there is a
hormone which is released on several different stimuli or moods or stress which is known as
endorphins.
Endorphins (endogenous morphine) are endogenous opioid neuro-peptides and peptide
hormones in humans and animals. They are produced by the central nervous system and
the pituitary gland. The term "endorphins" implies a pharmacological activity (analogous to
the activity of the corticosteroid category of biochemicals) as opposed to a specific chemical
formulation. It consists of two parts: endo- and -orphin; these are short forms of the
words endogenous and morphine, intended to mean "a morphine-like substance originating
from within the body". Endorphins, a multi-functional chemical, are emitted to counteract and
deal with sensations by transmitting electrical impulses through the body to the nervous
system. The principal function of endorphins is to inhibit the communication of pain signals
and they may also produce a feeling of euphoria very similar to that produced by other opioids.
Endorphins are naturally produced in response to pain but their production can also be
triggered by various activities. Vigorous aerobic exercise can stimulate the release of β-
endorphins, a potent μ-opioid receptor agonist, in the human and animal brain, which
contributes to a phenomenon known as a "runner's high". Laughing may also stimulate
endorphins production. β-endorphins are the best in pain relief and its production is hereditary,
due to this, its production level varies from animal to animal. High concentrations of
endorphins in the brain produce a sense of euphoria, enhance pleasure and suppress pain both
emotionally and physically. Low concentrations of endorphins in the animal’s brain feel
troubled and more aware of pain causes reduced the performance of the animals.
Endorphins inhibit pain perception. It is commonly called body’s natural analgesic or
endogenous opioid. It is produced at the time of physical or emotional stress such as
parturition. It binds to the same receptors that bind exogenous opiates. It affects animal
emotions and responsible for body feeling pleasure and produce a sense of euphoria.
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International Journal of Chemical Studies
Endorphins are morphine like in structure and has same
binding site in the brain cells or receptors. Endorphins are
released during different exercises, eating food, sex and
meditation, etc. Anxiety or nervousness in animals can be
treated with this endogenous endorphins without using any
medication or tablets, only the thing is that we must know
how and when endorphins is released. β-endorphins are
related to decreasing bodily stress and maintaining
homeostasis resulting in pain management, reward effects and
behavioral stability.
History of endorphins, synthesis, storage and secretion of
β-endorphins
Pert and Snyder, (1973) [27] discovered the “endogenous
opioid system”. In the year 1976, Simantov and Snyder
isolated endogenous opioid from the brain of a calf and term
is given "endorphin" (i.e. Endogenous morphine). Guillemin
and Schally, (1977) [16] won Noble price for their research and
findings on endorphins. Human and animals body produces at
least 20 different endorphins. Special four types are as
follows: (made all by 16 to 31 amino acids) Alpha (α)
endorphin, Beta (β) endorphin, Gamma (γ) endorphin and
Sigma (σ) endorphin β-endorphins are primarily synthesized
and stored in the anterior pituitary gland from their precursor
protein Proopiomelanocortin (POMC). However, recent
studies suggest that cells of the immune system are also
capable of β-endorphin synthesis because immune cells
possess mRNA transcripts for POMC and T-lymphocytes, B-
lymphocytes, monocytes and macrophages which have been
shown to contain endorphins during inflammation. POMC is a
large protein that is cleaved into smaller proteins such as β-
endorphin, alpha-melanocyte stimulating hormone -MSH),
adrenocorticotropin (ACTH) and others. The pituitary gland
synthesizes POMC in response to a signal from the
hypothalamus that signal being corticotropin-releasing
hormone (CRH). The hypothalamus releases CRH in response
to physiologic stressors such as pain, as in the postoperative
period. When the protein products of POMC cleavage
accumulate in excess, they turn hypothalamic CRH
production off - that is, feedback inhibition occurs.
Fig 1: Depicts the formation of β-endorphin from the POMC gene in the pituitary gland. Portions of the second and third exon of this gene make
up the POMC protein. The cleavage of the C-terminal end of this protein produces β-lipotropin, which is then cleaved again to form β-
endorphin. The POMC protein is also a precursor to other neuropeptides and hormones, such as adrenocorticotropic hormone.
Structure of β -Endorphins
β -Endorphin is peptide hormones (consist of chains of amino
acids), consist of 31 amino acid polypeptide
Sequence: Ac - Tyr - Gly - Gly - Phe - Met - Thr - Ser - Glu -
Lys - Ser - Gln - Thr - Pro - Leu - Val - Thr - Leu - Phe - Lys -
Asn - Ala - Ile - Ile - Lys - Asn - Ala His - Lys - Lys - Gly -
Gln OH.
Fig 2: Structure of β -Endorphins
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International Journal of Chemical Studies
Receptors of β endorphins and Factors stimulating the
release of β -endorphins
All of the endorphins bind to the µ-opioid receptors in the
brain. These analgesia- producing receptors are located in
brain, spinal cord and other nerve endings. β-endorphin
containing nerve fibers spread widely from neurons in the
hypothalamus to make inhibitory contacts with target neurons
to reduce pain. Receptors of endorphins are increased during
stressful conditions located on nervous system and immune
cells. Most of all immune cells produce endorphins.
.
Mechanism of action of β -endorphins
β-endorphins is released by pituitary (into blood) and
hypothalamus (into the spinal cord and brain). β-endorphins
containing nerve fibers spread widely from neurons in the
hypothalamus, to make inhibitory contacts with target neurons
to reduce pain. Free hormones are rapidly eliminated from
circulation through kidney or liver. The actions of β-
endorphins have been associated primarily with the central
nervous system and pain modulation. It may also be involved
in reproduction, exercise, stress and regulation of immune
function. The physiologic effects of the β-endorphins are
mediated through interactions with highly specific membrane
receptors. In the peripheral nervous system (PNS), β-
endorphins produce analgesia by binding to µ-opioid
receptors at both pre- and post- synaptic nerve terminals,
primarily exerting their effect through pre-synaptic binding.
When bound, a cascade of interactions results in inhibition of
the release of substance P, a key protein involved in the
transmission of pain. In the PNS, µ-opioid receptors are
present throughout peripheral nerves and have been identified
in the central terminals of primary afferent neurons,
peripheral sensory nerve fibers and dorsal root ganglia. In the
central nervous system, β-endorphins similarly bind µ-opioid
receptors and exert their primary action at pre-synaptic nerve
terminals. However, instead of inhibiting substance P, they
exert their analgesic effect by inhibiting the release of GABA,
an inhibitory neurotransmitter, resulting in excess production
of dopamine. Dopamine is associated with pleasure.
Role of β -endorphins in cancer
β-endorphins are natural neuropeptides secreted by anterior
pituitary gland through hypothalamus in response to stress.
Stress is also a one of the predisposing factor for cancer by
activating inflammatory mediators such as IL-1 and TNF-α,
involved in tumor progression. β -endorphins can be used for
natural antitumor activity by activating NK cells, macrophage
innate immune cells. Binding of β-endorphins to the receptors
on the immune cells, activates immune cells. β-endorphins
have an anti-carcinogenic activity by activating IFN-gamma,
NK cells and macrophages, which involve in antiviral
activity, apoptotic activity, decrease cellular proliferation and
alters the environment of gene expression in tumor
microenvironment (Zhang, 2015) [34]. Supplementation of β-
endorphin neurons through transplants prevented carcinogen-
induced mammary tumorigenesis and tumor metastasis. When
the β-endorphins transplants were given at the early stage of
tumor development, many tumors were destroyed, possibly
because of increased innate immune activity and the surviving
tumors lost their ability to progress to high-grade cancer
owing to β-endorphins cells' suppressive effects on epithelial
mesenchymal transition regulators. Another remarkable effect
of the β-endorphin transplantation was that it promoted the
activation of the innate immune (NK cells and macrophages)
activity, following tumor cell invasion, to such an extent that
tumor cell migration to another site was completely halted.
NK cells and macrophages are critical components of the
innate immune system and play a vital role in host defense
against tumor cells. Hence, the increased level of innate
immunity may have caused unfavorable conditions for cancer
cell survival. In the β-endorphin celltreated animals, the
lower inflammatory milieu that was achieved by the higher
level of anti-inflammatory cytokines and the lower level of
inflammatory cytokines may have also been involved in
inhibiting cancer growth and transformation. β-endorphins
suppress the sympathetic neuronal function and stimulate the
parasympathetic neuronal activity results activation of
peripheral immunity and anti-inflammatory cytokines to
control tumor growth and progression.
β-endorphins neuronal cells in the hypothalamus control the
neoplastic growth and progression of tumor cells, likely by
modulating one or more of the factors indicated. Effects
include the activation of parasympathetic nervous system
control of lymphoid organs, causing activation of innate
immune cells (macrophages and NK cells) and an increase in
anti-inflammatory cytokine levels in the circulation. The HPA
axis and subsequent stress hormones released from the
adrenal gland and sympathetic nerve terminals
(glucocorticoids and catecholamines) may also be suppressed.
In a tumor microenvironment, these hormonal and cytokine
changes down regulate inflammation-mediated epithelial
mesenchymal transition (EMT) and thereby, suppress cancer
progression. Collectively, these effects create an unfavorable
environment for tumor initiation, growth and progression.
neoplastic growth and progression of tumor cells, likely by
modulating one or more of the factors indicated. Effects
include the activation of parasympathetic nervous system
control of lymphoid organs, causing activation of innate
immune cells (macrophages and NK cells) and an increase in
anti-inflammatory cytokine levels in the circulation. The HPA
axis and subsequent stress hormones released from the
adrenal gland and sympathetic nerve terminals
(glucocorticoids and catecholamines) may also be suppressed.
In a tumor microenvironment, these hormonal and cytokine
changes down regulate inflammation-mediated epithelial
mesenchymal transition (EMT) and, thereby, suppress cancer
progression. Collectively, these effects create an unfavorable
environment for tumor initiation, growth, and progression.
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International Journal of Chemical Studies
Fig 3: β-Endorphin neuronal cells in the hypothalamus control the
Role of β -endorphins in inflammation
In inflammatory condition recruitment of immune cells to the
site of inflammation by chemokines produce endorphins, acts
as Anti-inflammatory activity of β-endorphins by activating
anti-inflammatory cytokines such as IL-18, IL-10, IFN-
Gamma and decreasing pro-inflammatory cytokines such as
IL-1, IL-6 and TNF-α mediated release of COX-2
inflammatory mediator activates key transcription factors NF-
KB and STAT-3 involved in tumor progression by cellular
proliferation, cell survival, angiogenesis, genomic instability,
immune suppression, invasion and metastasis. β-endorphins
suppress NF-KB transcription factor activity, there by
inhibiting the mutation and suppression of P53 tumor
suppressor gene. It also involved in epithelial expression of E-
Cadherin induced cell adhesion, loss of E-Cadherin involved
in epithelial to mesenchymal transition induced tumor
invasion. The stress of inflammation triggers the release of
corticotrophin-releasing hormone (CRH). The endorphin-
producing cells have receptors for CRH, which then facilitate
the release of endorphins. Immune cells also have receptors
for endorphin indicating an autocrine/paracrine effect of
endorphin on the immune cells modulating signal
transmission of inflammation, the production of cytokines and
its progress. The increased level of endorphins, in the
systemic circulation during inflammation may originate from
the pituitary as well as from peripheral immune cells. Resting
plasma β-endorphins levels as a clinically useful predictor of
opioid analgesic responses. The evaluation of β-endorphins
levels in body fluids might be useful as a marker for disease
diagnosis and treatment (Mousa et al., 2004) [23].
Role of β -endorphins in immunity
β-endorphins receptors are present on most of all immune
cells such as neutrophils, T-lymphocytes, B-lymphocytes,
macrophages, NK cells, dendritic cells binds with β-
endorphins results in activation of innate and adaptive
immune cells such as NK cells, macrophages, T cell
proliferation, B cells results in release of IFN-Gamma,
Perforin, Granzyme-B and antibodies.
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International Journal of Chemical Studies
Fig 4: Schematic depiction of β-endorphins release from immune cells of the innate and adaptive immune system. Neutrophils,
monocytes/macrophages and T-cells migrate into inflamed tissue in response to chemokines. Release of β-endorphins (green circles) is triggered
by cytokines, chemokines and bacterial products. β-endorphins bind to opioid receptors (green) expressed in peripheral sensory neurons
(yellow). This cascade causes peripheral antinociception.
Receptors for endorphin have been identified on leukocytes.
A number of in vitro studies have demonstrated the ability of
opioids to influence immune function, such as lymphocyte
proliferative responses, natural killer cell activity and
granulocyte activity. Recent research has also demonstrated
the production of β-endorphin and ACTH by cells of the
immune system, along with the expression of the endorphin
genes. Although it appears that endogenous opioids are
released in response to various forms of stress and in turn
interact with cells of the immune system thereby modulating
immune function (Mambretti et al., 2016) [22].
Role of β-endorphins in pain modulation
β-endorphins had a potent analgesic effect and 18 to 33 times
more potent compared to morphine on a molar basis (Loh et
al., 1976) [21]. β-endorphins is packaged in membrane-bound
secretory vesicles ready to be released when required. In the
peripheral nervous system β-endorphins binds to µ-opioid
receptors results in decreased release of substance P, a
neurotransmitter of pain and inflammation results in analgesic
activity and reduce inflammation.
In the central nervous system, β-endorphins binds to µ-opioid
receptors results in decrease GABA neuro-inhibitory
transmitter and release of dopamine neurostimulatory
neurotransmitter results in analgesic, euphoric, self-reward,
cognitive development of brain.
Fig 5: β-endorphins and pain modulation
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International Journal of Chemical Studies
Fig 6: Analgesic effect of β-endorphins.
Role of β-endorphins in stress
Endorphins may play a role in the defensive response of the
organism to stress. It may function as trophic hormones in
peripheral target organs such as the adrenal medulla and the
pancreas and mediate adrenaline and glucagon release in
response to stress. It plays a role in the control of the pituitary
gland during stress. It plays a role in the behavioral
concomitants of stress. It has the ability to inhibit stress
hormone production and produce analgesia and a feeling of
well-being. It has a stress reducing activity by suppressing
hypothalamic pituitary adrenal (HPA)-axis activated in
response to stress, release corticotropic releasing hormone and
norepinephrine and neuropeptides through sympathetic
nervous system activity.β-endorphins neuronal cell bodies are
primarily localized in the arcuate nuclei of the hypothalamus
and its terminals are distributed throughout the CNS,
including the paraventricular nucleus of the hypothalamus. In
the paraventricular nucleus, these neurons innervate CRH
neurons and inhibit CRH release. During stress, secretion of
CRH and catecholamine stimulates secretion of hypothalamic
β-endorphins and other pro-opiomelanocortin-derived
peptides, which in turn inhibit the activity of the HPA axis. β-
endorphins are known to bind to μ-opioid receptors to
modulate the neurotransmission in neurons of the ANS via
neuronal circuitry within the paraventricular nucleus
(Guillemin et al., 1977) [15].
In the CNS, the β-endorphins have rewarding and reinforcing
properties and to be involved in stress response. Stress has
been associated with depression of the immune system. β-
endorphins are one of the potential mediators of stress-
induced immune-modulation. The role of stress in immune
function appears to require an interaction between the brain
and the immune system. Current research suggests that
bidirectional communication exists between the immune and
the central nervous systems.
β-endorphins influence adrenaline synthesis and storage and
to stimulate adrenaline release from the adrenal medulla
directly (Kvemansky, 1970) [20]. β-endorphins have been
reported to stimulate in vitro corticosterone synthesis. Since
some opiate receptor binding sites occur in the adrenal cortex.
It is conceivable that endorphin, like ACTH, could exert some
corticotropic effects in animals, when released into the
circulation in response to stress (Shanker et al., 1979). β-
endorphin, has been elevated due to exposure to stress. Sheep
respond with elevated plasma β-endorphin following stressful
procedures such as tail docking, castration, skin pinching and
isolation. Dairy cows respond with elevated circulating levels
of β-endorphin when placed in an unfamiliar room for
milking. Surgical castration had a much greater effect on
plasma β-endorphin and cortisol concentrations than the
psychological stressors of weaning, isolation and shearing
restraint (Bruckmaier et al., 1994) [14].
Role of β-Endorphins in Puberty
The onset of puberty initiates changes in somatic growth and
gonadal maturation. It depends on the activation of the
hypothalamic gonadotropin-releasing hormone (GnRH) pulse
generator, resulting in pulsatile GnRH secretion and
subsequently pituitary gonadotropin secretion. Hypothalamus
generates the pulsatile release of GnRH, resulting in the onset
of puberty. β -endorphins influence to the onset of puberty.
Studies suggest that maturation of the hypothalamic-pituitary-
ovarian axis may be due to a decrease in hypothalamic
pituitary sensitivity to the inhibitory effects of β -endorphins.
Thus, β -endorphins, appears to provide a greater inhibitory
influence on LH secretion before puberty than after the
completion of puberty. Puberty in the female is accompanied
by a marked attenuation of the opioid inhibition of luteinizing
hormone secretion. One factor which may contribute to this
altered role is a change in the metabolism of opioid peptides
during sexual maturation (Wiemann et al., 1989) [33].
Role of β -endorphins in the testis
β-endorphins has a regulatory influence on the reproductive
function at the level of the hypothalamic-pituitary gonadal
axis. Immunohistochemical evidence shows that β-endorphin
is present in the leydig cells of fetal, neonatal and adult
animal. β-endorphins synthesis localized in the leydig cells
leading to the hypothesis of a direct function of the peptide in
the reproductive organs (Albrizio et al., 2006) [1]. The
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International Journal of Chemical Studies
presence of high-affinity opioid binding sites in Sertoli cells
of the testes. β-endorphins treatment of the Sertoli cells
inhibits basal and FSH-stimulated androgen-binding protein
production. No opiate binding on leydig cell. Acute or chronic
β-endorphin treatment does not affect testosterone production
by leydig cells in vitro, consistent with the absence of
receptors on these cells (Nerea et al., 2011) [24]. A novel
biochemical tool for the diagnosis and treatment of male
infertility could be based upon components of the opioid
system. The presence of the opioid system in sperm cells also
represents a novel opportunity for reproductive management,
for either enhancing the probability of fertilization or reducing
it through the development of novel targeted contraceptives
(Gerendai et al., 1984) [11].
At the level of the CNS, β -endorphins regulate reproductive
function by inhibiting the secretion of GnRH, thereby
suppressing the release of LH and sex hormonal steroids such
as testosterone and estradiol. Because of the shortcomings of
currently available methods of male contraception, opioid
system may contribute to develop additional non-hormonal
male contraceptive since currently available methods require
the administration of exogenous testosterone (Amory, 2005).
In the testis, β -endorphins are mainly synthesized de novo by
leydig cells and Sertoli cells and it appear to be able to inhibit
Sertoli cell function in an autocrine and paracrine manner.
The detection in sperm cells of β -endorphins, specific
enzymes for their degradation and opioid receptors suggests
that the opioid system may contribute to sperm fertility, and β
-endorphin may be used as a biochemical tool for the
diagnosis and treatment of the human male fertility. These
findings open up a novel area of therapeutic exploitation of
the treatment of male infertility (Garrido, 2008) [12].
Fig 7: Effect of β-endorphins on male reproductive system
Role of β-endorphins in pregnancy
When measuring plasma concentrations in first, second, and
third trimester pregnancies, we found a significant lowest
during the second trimester and highest in third trimester
pregnancies. Genazzani et al. (1981) [13] reported a significant
decrease in maternal plasma β-endorphin at 9-12 weeks
gestation and an increase near full term (36-37 weeks)
gestation when compared with those found in non-pregnant
controls. Maternal plasma β- endorphin concentrations higher
in pregnant animal in comparison to non pregnant animals
(Goland et al., 1981) [14]. During labour, maternal plasma β-
endorphin concentrations rise and remain high during the
early postpartum period. This is most consistent with the
increase in secretion of ACTH that has been reported to occur
during labour and to peak at delivery. Csontos et al. (1979) [8]
reported parallel increases in maternal plasma β-endorphin
and ACTH concentrations. Maternal plasma β- endorphin
concentrations remain raised for some time after delivery,
despite the short half life of β- endorphin, indicates that the
maternal pituitary continues to secrete increased amounts of
β-endorphins after delivery. β-endorphins increase during
labour and peak at parturition. Endorphins are natural
substances, which are released whenever the body is
physically stressed. Once labour begins, the level of
endorphins rises, helping the mother to cope with her
contractions and to get some rest in between. β-endorphins is
an endogenous anti-nociceptive neuropeptide and an
important pain biomarker in pregnant cows (Csontos et al.,
1979) [8].
Role of β- endorphins and the fetus
Plasma β-endorphin concentrations are a measure of stress not
only in the mother but also in the fetus. β-endorphin increases
in the fetal circulation in response to stress. Inverse
correlation between umbilical plasma β-endorphin
concentrations and Partial pressure of arterial oxygen (PaO2)
and pH, indicating that fetal hypoxia or acidosis, or both, may
be related to endorphins release (Wardlaw et al., 1979).
Umbilical venous plasma endorphin concentrations are higher
than umbilical arterial plasma endorphin concentrations
suggesting that the placenta contributes to the pool of
circulating fetal β-endorphins. In the presence of fetal distress,
Control of male reproductive function by the opioid system at
multiple levels.
(1) At the level of the CNS, β-endorphin inhibit the secretion
of GnRH, thereby suppressing the release of LH from the
pituitary.
(2) At the testes level, β-endorphin are synthesized mainly in
Leydig cells after LH stimulation, and they exert an
inhibitory effect on Sertoli cells. In particular, β-
endorphin can regulate the levels of testosterone (T)
indirectly, inhibiting the production of ABP that is
stimulated by FSH in Sertoli cells.
(3) Genes encoding opioid peptide precursors are
differentially expressed in germ cells, and somatic cells of
the testes and their transcripts are not efficiently translated
in spermatogenic germ cells.
(4) In spermatozoa, the opioid system regulates sperm
motility in a distinct manner by the activation of distinct
receptors
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International Journal of Chemical Studies
however, umbilical arterial endorphin concentrations seem to
rise more extensively than umbilical venous concentrations,
suggesting that the fetal pituitary is capable of secreting β-
endorphin in response to stress.
Fachinetti et al. (1982) [10] reported that β endorphin is present
in the plasma of newborn animals during the first 24 hours of
life. The fetus born at full term is capable of producing
endorphins by release from the pituitary. That CRH secreted
in response to stressful stimuli may not only initiate the
selective cleavage of ACTH but also that of endorphins from
their common precursor pro-opiomelanocortin in the fetus and
newborn. Hypoxia may be the overriding stress stimulus in
the fetus, and β-endorphin in the fetal central nervous system
may act as neurotransmitters that modulate fetal heart rate
patterns and decrease fetal heart rate variability.
Role of β-endorphins in aging
It also has an anti-aging activity by decreasing release of free
radicals (ROS, RNS) from immune cells such as neutrophils,
macrophages, dendritic cells and cytokines such as IL-1, IL-8,
TNF-α during oxidative burst, which is involved in DNA
damage, genetic mutation, cell aging, cell death and β-
endorphins involved in lengthening of telomeres, which
otherwise shorten with aging. Endorphin reduces or removes
superoxide and retards aging process (Shrihari, 2017) [28].
β-endorphins and milking
β-endorphin is involved in the endocrinological response to
suckling in animals. Elevated plasma β-endorphins
concentrations in unfamiliar surroundings in dairy cows.
When cows get acclimatize to the new surroundings, the
concentrations of the hormones decreases. These observations
β-endorphin that play a role within the mechanisms causing
central inhibition of milk ejection; hence, the exogenous
opioid morphine inhibited both oxytocin release and milk
ejection. In emotional stress situations, the release of oxytocin
from the pituitary is inhibited with simultaneously elevated β-
endorphin levels in dairy cows. Moreover, a decrease of
plasma β-endorphin concentrations during machine milking in
cows. β-endorphin releases was not affected by milking
frequency and not correlated with the magnitude of prolactin
release (Bruckmaier, 1994) [14].
Role of β-endorphins during exercise
Physical activity is thought to induce significant β-endorphin
release. During continuous exercise there is release of
endorphin and the effect is called Runner’s high. When the
athlete crosses the limit of his exercise then endorphins are
released which reduces the pain by stopping the pain signals
and the athlete is able to work out for more time even after his
threshold limit is over. In heart patients who had an attack
before, are always advised to do regular exercise, the reason
for this is during exercise endorphin is released and it protects
the heart from an attack. And if, does the heart attack comes,
instead of getting frightened and panic, it gives the patient the
strength to fight against it for a long time till he is hospitalized
and becomes healthy very soon. There is a very rare
possibility that a man who is continuously exercising has an
second attack. A positive attitude is generated by the release
of these hormones (Hausenblas and Downs, 2002) [18].
When we exercise, our body releases chemicals called
endorphins. These endorphins interact with the receptors in
your brain that reduce your perception of pain. Endorphins
also trigger a positive feeling in the body. Regular exercise
has been proven to reduce stress and improve sleep. Exercise
helps bump up the production of your brain's feel-good
neurotransmitters, called endorphins. Although this function
is often referred to as a runner's high, endorphins increases
self-confidence, it relaxes you, and it can lower the symptoms
associated with mild depression and anxiety. Endorphins can
also improve your sleep, which is often disrupted by stress,
depression and anxiety (Biddle and Mutrie, 1991) [3].
Fig 8: The brain before and after 20 minutes vigorous exercise
Role of β -endorphins in emotions
Endorphins are produced as a response to certain stimuli,
especially stress, fear or pain. They originate in various parts
of the body like pituitary gland, spinal cord and throughout
parts of nervous system and interact mainly with receptors in
cells found in regions of the brain responsible for blocking
pain and controlling emotion (Dalayeun, 1993) [9]. Music
releases endorphins in the blood and changes the mood.
Change in mood is directly proportional to endorphin.
Endorphin also protects us from stress, hypertension,
depression and heart attacks. Endorphin is released during
stress and hypertension and these endorphins bind to the µ-
opioid receptors in neurons which block the release of
neurotransmitters and in turn block the pain signals going to
the brain (Chaudhary, 2004) [7]. Music has a role in reducing
stress and inhibit the secretion of cortisol (Hebert, 2005).
During coitus endorphins are released, it gives the blissful and
happy feeling and due to release of endorphins females look
too young and charming. It’s the endorphins effect which is
released during sex that brings the charm and shining on the
face of the married girl. Laughing releases the endorphin
which keeps you happy and healthy (Best, 2007) [5].
Role of β -endorphins in acupuncture therapy
In acupuncture therapy when needles are inserted at the fixed
points in the body, there is pain while inserting not one but
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International Journal of Chemical Studies
several needles due to which endorphin is released, which
releases the feeling of pain and subject easily goes through
this therapy. Mechanisms how acupuncture stimulates the
immune system through β-endorphin are the described as
acupuncture stimulation of ST36 acupoint induces release of
nitric oxide (NO). NO, a neurotransmiter, stimulates via the
sensory nerves, spinal cord and medulla oblongata, gracile
nucleus the lateral hypothalamic area (LHA), where it
promotes secretion of opioid peptides such as β-endorphin. β-
endorphin travels via blood circulation to the spleen and other
body locations containing immune cells where it binds to
opioid receptors expressed on the surface of NK cells and
stimulates NK cells to amplify their expression of cytotoxic
molecules and consequently tumoricidal activity, and
production of IFN-γ. This cytokine induces the expression of
NK cell receptors and cytokine receptors on NK cells and
perhaps cytokine secretion by other immune cells, thereby
orchestrating and further amplifying anticancer immune
functions (Nopadow et al., 2008) [25].
Fig 9: Mechanisms how acupuncture stimulates the β-endorphin production and affect the immune system
Conclusion
Exercises such as walking, running, workouts, laughing
exercise, meditation, listening music and all these are
responsible for the release of endorphins hormone or they are
the stimuli to release this hormone which gives them strength,
confidence and gives mood of well being and happy. In
anxiety patients endorphin is given orally, but, instead of
taking pills orally one can make use of original endorphins
present in the body as a medicine. Only the thing is the
subject must know how endorphins are released in his body
and what he has to do for it. Also in anxiety patients music
gives a great relaxation to their brain and mind and the patient
feel more peaceful and happy. Medication and high dose
tablets harm the immune system making us vulnerable to
many diseases, but exercise releases endorphins which keeps
us healthy happy curing many diseases and it never interrupts
with the immune system. β-endorphins are one of the
abundant type of endorphins has various activities such as
immune-stimulatory, analgesic, stress reducer and anti-
inflammatory activity. β-endorphins are neuropeptides
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International Journal of Chemical Studies
involved in pain management, possessing morphine like
effects and are involved in natural reward circuits such as
feeding, drinking, sex and maternal behavior. Therefore, more
studies are necessary for understanding of β-endorphins and
their dose dependent action is helpful for future preventive,
therapeutic, and holistic treatment of various diseases such as
autoimmune diseases, cancer and infectious diseases without
adverse drug effects which is inexpensive.
References
1. Albrizio M, Guaricci AC, Calamita G, Zarrilli A, Minoia
P. Expression and immunolocalization of the mu-opioid
receptor in human sperm cells. Fertility and Sterility.
2006; 86:1776-9.
2. Amory JK. Male hormonal contraceptives: current status
and future prospects. Endocrinology. 2005; 4:333341
3. Biddle S, Mutrie N. Psychology of physical activity and
exercise: A health related perspective. 2nd Edn., Springer
Verlag London Ltd, 1991, 25
4. Bruckmaier RM, Schams D, Blum JW. Continuously
elevated concentrations of oxytocin during milking are
necessary for complete milk removal in dairy cows.
Journal of Dairy Research. 1994; 61:323-334.
5. Best B. Brain Neuron Physiology online, 2007.
http://www.benbest.com/science//anatmd1.html.
6. Calogero A, Gallucci W, Gold P, Chrousos G. Multiple
feedback regulatory loops upon rat hypothalamic
corticotropin-releasing hormone secretion. The Journal of
Clinical Investigation. 1988; 82:767-774.
7. Chaudhary L. Brain Workout. South China Morning
Post, online, 2004.
8. Csontos K, Rust M, Hollt V, Mahr W, Kromer W,
Teschemacher HJ. Elevated plasma & endorphins levels
in pregnant women and their neonates. Life Science.
1979; 25:835-844.
9. Dalayeun JF. Physiology of β-endorphins a close-up view
and a review of the literature. Biomedicine and
Pharmacotherapy. 1993; 47(8):26-35.
10. Fachinetti F, Bagnoli F, Bracci R, Genazzani AR. Plasma
opioids in the first hours of life. Pediatric Research. 1982;
16:95-98.
11. Gerendai I, Shaha C, Thau R, Bardin CW. Do testicular
opiates regulate leydig cell Function. Endocrinology.
1984; 115:1645-1647.
12. Garrido N. Contribution of sperm molecular features to
embryo quality and assisted reproduction success.
Reproductive Biomedicine. 2008; 17:855-865.
13. Genazzani AR, Facchinetti F, Parrini D. β-Lipotropin and
β-endorphins plasma levels during pregnancy. Clinical
Endocrinology. 1981; 14:409-418.
14. Goland RS, Wardlaw SL, Stark RI, Fran AG. Human
plasma β-endorphins during pregnancy, labor and
delivery. Journal of clinical Endocrinology and
Metabolism. 1981; 52:74-78.
15. Guillemin R, Vargo T, Rossier J. Beta-Endorphin and
adrenocorticotropin are secreted concomitantly by the
pituitary gland. Journal of Biology Science. 1977;
197:136139.
16. Guillemin R, Schally AW. The Nobel Prize in
Physiology or Medicine. Press release, 1977.
17. Guyton AC, Hall JE. Text book of Medical Physiology,
10th Edn., W B Saunders, 2001, 556.
18. Hausenblas HA, Downs DS. Exercise dependence: a
systematic review. Psychological Sport Exercise. 2002;
3:89-123.
19. Hebert S, Beland DR, Crete OM. Physiological stress
response to vidio-game playing the contribution of buil-in
music. Life Sciences. 2005; 76:2371-2380.
20. Kvemansky R, Weise VK, Kopin IJ. Elevation of adrenal
tyrosine hydroxylase and Penylethanolamine-Nmethyl
transferase by repeated immobilization of rats. Journal of
Endocrinology. 1970; 25:744-749.
21. Loh HH, Tseng LF, Li CH. Beta-endorphin is a potent
analgesic agent. In: Proceedings of the National
Academy of Sciences of the United States of America.
1976; 73(8):28-35.
22. Mambretti EM, Kistner K, Mayer S, Massotte D, Kieffer
BL, Hoffmann C. Functional and structural
characterization of axonal opioid receptors as targets for
analgesia. Molecular Pain. 2016; 1:12-14.
23. Mousa S, Shakibaei M, Sitte N, Schäfer M, Stein C.
Subcellular pathways of beta-endorphin synthesis,
processing and release from Immunocytes in
inflammatory pain. Endocrinology. 2004; 145(3):1331-
1341.
24. Nerea S, Casis L, Irazusta J. Regulation of male fertility
by the opioid System. Molecular Medicine. 2011;
17(7):846-853
25. Nopadow V, Ahn A, Longhurst J, Lao L, Stener VE,
Harris R et al. The status and future of acupuncture
clinical research. Journal of Alternative and
Complementary Medicine. 2008; 14(7):861-869.
26. Nuller YL, Morozova MG, Kushnir ON, Hamper N.
Effect of naloxone therapy on depersonalization disorder.
Journal of Psychopharmacological. 2001; 5(2):93-95.
27. Pert CB, Snyder SH. Opiate receptor demonstration in
nervous tissue. Science. 1973; 179(4077):1011-14.
28. Shrihari TG. Quantum healing approach to new
generation of holistic healing. Journal of Translational
Medicine. 2017; 7:195-198.
29. Shanker G, Sharma RK. β-endorphins stimulate
corticosterone synthesis. Biochemical and Biophysical
Research Communications. 1979; 86:1-5.
30. Simantov R, Snyder SH. Morphine-like peptides in
mammalian brain, isolation, structure, elucidation, and
interactions with the opiate receptor. In: Proceedings of
the National Academy of Sciences of the United States of
America. 1976; 73(7):2515-19.
31. Simeon D. An open trial of naltrexone in the treatment of
depersonalization disorder. Journal of Clinical
Psychopharmacology. 2011; 10:11-13.
32. Wardlaw SL, Stark RI, Baxi L, Frantz AG. Plasma β-
endorphin and lipotropin in the human fetus at delivery:
Correlation with arterial pH and PO2. Journal of clinical
Endocrinology and Metabolism. 1979; 49:888-891.
33. Wiemann JN, Clifton DK, Steiner RA. Pubertal changes
in gonadotropin-releasing hormone and
Proopiomelanocortin gene expression in the brain of the
male rat. Endocrinology. 1989; 124(4):1760-67.
34. Zhang C, Murugan S, Boyadjieva N, Jabbar S,
Shrivastava P. β-endorphin cell therapy for cancer
prevention. Cancer Prevention Research. 2015; 8:56-67.
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