[Show abstract][Hide abstract] ABSTRACT: The regulation of calcium (Ca(2+)) homeostasis by beta-adrenergic receptor (βAR) activation provides the essential underpinnings of sympathetic regulation of myocardial function as well as a basis for understanding molecular events that result in hypertrophic signaling and heart failure. Sympathetic stimulation of the βAR not only induces protein phosphorylation but also activates nitric oxide (NO)-dependent signaling, which modulates cardiac contractility. Nonetheless, the role of NO in βAR-dependent regulation of Ca(2+) handling has not yet been explicated fully.
To elucidate the role of protein S-nitrosylation, a major transducer of NO bioactivity, on βAR-dependent alterations in cardiomyocyte Ca(2+) handling and hypertrophy.
Using transgenic mice to titrate the levels of protein SNO, we uncovered major roles for protein S-nitrosylation generally, and for phospholamban (PLN) and cardiac troponin C (cTnC) S-nitrosylation in particular, in βAR-dependent regulation of Ca(2+) homeostasis. Notably, S-nitrosylation of PLN consequent upon βAR stimulation is necessary for its inhibitory pentamerization of PLN, which activates sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) and increases cytosolic Ca(2+) transients. Coincident S-nitrosylation of cTnC decreases myocardial sensitivity to Ca(2+). During chronic adrenergic stimulation, global reductions in cellular S-nitrosylation mitigate hypertrophic signaling resulting from Ca(2+) overload.
S-nitrosylation operates in concert with phosphorylation to regulate many cardiac Ca(2+)-handling proteins, including PLN and cTnC, thereby playing an essential and previously unrecognized role in cardiac Ca(2+) homeostasis. Manipulation of the S-nitrosylation level may prove therapeutic in heart failure.
Full-text · Article · Aug 2015 · Circulation Research
[Show abstract][Hide abstract] ABSTRACT: The innate and adaptive immune system plays an important role in diverse forms of central nervous system (CNS) pathologies including neurodegenerative diseases and peripheral nerve injury. Evidence for an innate inflammatory response in Alzheimer’s disease (AD) was described 20 years ago, and subsequent studies have documented roles of inflammation in Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and a growing number of other CNS pathologies. Although inflammation may not be the initiating factor for neurodegenerative pathologies, experimental data suggests that persistent inflammatory responses involving microglia and astrocytes, as well as blood monocyte-derived macrophages, clearly contribute to disease progression.
High levels of hydrogen sulfide exert toxic effects to CNS. On the other hand, low and physiological levels of H2S may have beneficial effects on number of tissues including CNS. For example, a number of studies have reported that H2S exerts anti-inflammatory and anti-apoptotic effects in CNS. In this chapter, studies related to the role of H2S in neuroinflammation and neurodegeneration will be reviewed and discussed. In particular, we will focus on the role of H2S in neuroinflammation associated with PD.
No preview · Article · Jul 2015 · Handbook of experimental pharmacology
[Show abstract][Hide abstract] ABSTRACT: Therapeutic hypothermia (TH) improves neurological outcomes after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Although nitric oxide prevents organ injury induced by ischemia and reperfusion, role of nitric oxide during TH after CPR remains unclear. In this article, the authors examined the impact of endogenous nitric oxide synthesis on the beneficial effects of hypothermia after CA/CPR. The authors also examined whether or not inhaled nitric oxide during hypothermia further improves outcomes after CA/CPR in mice treated with TH.
Wild-type mice and mice deficient for nitric oxide synthase 3 (NOS3) were subjected to CA at 37°C and then resuscitated with chest compression. Body temperature was maintained at 37°C (normothermia) or reduced to 33°C (TH) for 24 h after resuscitation. Mice breathed air or air mixed with nitric oxide at 10, 20, 40, 60, or 80 ppm during hypothermia. To evaluate brain injury and cerebral blood flow, magnetic resonance imaging was performed in wild-type mice after CA/CPR.
Hypothermia up-regulated the NOS3-dependent signaling in the brain (n = 6 to 7). Deficiency of NOS3 abolished the beneficial effects of hypothermia after CA/CPR (n = 5 to 6). Breathing nitric oxide at 40 ppm improved survival rate in hypothermia-treated NOS3 mice (n = 6) after CA/CPR compared with NOS3 mice that were treated with hypothermia alone (n = 6; P < 0.05). Breathing nitric oxide at 40 (n = 9) or 60 (n = 9) ppm markedly improved survival rates in TH-treated wild-type mice (n = 51) (both P < 0.05 vs. TH-treated wild-type mice). Inhaled nitric oxide during TH (n = 7) prevented brain injury compared with TH alone (n = 7) without affecting cerebral blood flow after CA/CPR (n = 6).
NOS3 is required for the beneficial effects of TH. Inhaled nitric oxide during TH remains beneficial and further improves outcomes after CA/CPR. Nitric oxide breathing exerts protective effects after CA/CPR even when TH is ineffective due to impaired endogenous nitric oxide production.
[Show abstract][Hide abstract] ABSTRACT: Physiological levels of H2S exert neuroprotective effects, whereas high concentrations of H2S may cause neurotoxicity in part via activation of NMDAR. To characterize the neuroprotective effects of combination of exogenous
H2S and NMDAR antagonism, we synthesized a novel H2S-releasing NMDAR antagonist N-((1r,3R,5S,7r)-3,5-dimethyladamantan-1-yl)-4-(3-thioxo-3H-1,2-dithiol-4-yl)-benzamide (S-memantine) and examined its effects in vitro and in vivo. S-memantine was synthesized by chemically combining a slow releasing H2S donor 4-(3-thioxo-3H-1,2-dithiol-4-yl)-benzoic acid (ACS48) with a NMDAR antagonist memantine. S-memantine increased intracellular
sulfide levels in human neuroblastoma cells (SH-SY5Y) 10-fold as high as that was achieved by ACS48. Incubation with S-memantine
after reoxygenation following oxygen and glucose deprivation (OGD) protected SH-SY5Y cells and murine primary cortical neurons
more markedly than did ACS48 or memantine. Glutamate-induced intracellular calcium accumulation in primary cortical neurons
were aggravated by sodium sulfide (Na2S) or ACS48, but suppressed by memantine and S-memantine. S-memantine prevented glutamate-induced glutathione depletion in
SH-SY5Y cells more markedly than did Na2S or ACS48. Administration of S-memantine after global cerebral ischemia and reperfusion more robustly decreased cerebral
infarct volume and improved survival and neurological function of mice than did ACS48 or memantine. These results suggest
that an H2S-releasing NMDAR antagonist derivative S-memantine prevents ischemic neuronal death, providing a novel therapeutic strategy
for ischemic brain injury.
[Show abstract][Hide abstract] ABSTRACT: Sudden cardiac arrest (CA) is one of the leading causes of death worldwide. Previously we demonstrated that administration of sodium sulfide (Na(2)S), a hydrogen sulfide (H(2)S) donor, markedly improved the neurological outcome and survival rate at 24h after CA and cardiopulmonary resuscitation (CPR) in mice. In this study, we sought to elucidate the mechanism responsible for the neuroprotective effects of Na(2)S and its impact on the long-term survival after CA/CPR in mice.
Adult male mice were subjected to potassium-induced CA for 7.5min at 37°C whereupon CPR was performed with chest compression and mechanical ventilation. Mice received Na(2)S (0.55mgkg(-1) i.v.) or vehicle 1min before CPR.
Mice that were subjected to CA/CPR and received vehicle exhibited a poor 10-day survival rate (4/12) and depressed neurological function. Cardiac arrest and CPR induced abnormal water diffusion in the vulnerable regions of the brain, as demonstrated by hyperintense diffusion-weighted imaging (DWI) 24h after CA/CPR. Extent of hyperintense DWI was associated with matrix metalloproteinase 9 (MMP-9) activation, worse neurological outcomes, and poor survival rate at 10 days after CA/CPR. Administration of Na(2)S prevented the development of abnormal water diffusion and MMP-9 activation and markedly improved neurological function and long-term survival (9/12, P<0.05 vs. Vehicle) after CA/CPR.
These results suggest that administration of Na(2)S 1min before CPR improves neurological function and survival rate at 10 days after CA/CPR by preventing water diffusion abnormality in the brain potentially via inhibiting MMP-9 activation early after resuscitation.
[Show abstract][Hide abstract] ABSTRACT: The role of hydrogen sulfide (H(2)S) in endotoxin (lipopolysaccharide [LPS])-induced inflammation is incompletely understood. We examined the impact of H(2)S breathing on LPS-induced changes in sulfide metabolism, systemic inflammation, and survival in mice.
Mice that breathed air alone exhibited decreased plasma sulfide levels and poor survival rate at 72 h after LPS challenge. Endotoxemia markedly increased alanine aminotransferase (ALT) activity and nitrite/nitrate (NOx) levels in plasma and lung myeloperoxidase (MPO) activity in mice that breathed air. In contrast, breathing air supplemented with 80 ppm of H(2)S for 6 h after LPS challenge markedly improved survival rate compared to mice that breathed air alone (p<0.05). H(2)S breathing attenuated LPS-induced increase of plasma ALT activity and NOx levels and lung MPO activity. Inhaled H(2)S suppressed LPS-induced upregulation of inflammatory cytokines, while it markedly induced anti-inflammatory interleukin (IL)-10 in the liver. Beneficial effects of H(2)S inhalation after LPS challenge were associated with restored sulfide levels and markedly increased thiosulfate levels in plasma. Increased thiosulfate levels after LPS challenge were associated with upregulation of rhodanese, but not cystathionine-γ-lyase (CSE), in the liver. Administration of sodium thiosulfate dose-dependently improved survival after LPS challenge in mice.
By measuring changes in plasma levels of sulfide and sulfide metabolites using an advanced analytical method, this study revealed a critical role of thiosulfate in the protective effects of H(2)S breathing during endotoxemia.
These observations suggest that H(2)S breathing prevents inflammation and improves survival after LPS challenge by altering sulfide metabolism in mice.
[Show abstract][Hide abstract] ABSTRACT: Sudden cardiac arrest (CA) is a leading cause of death worldwide. Breathing nitric oxide (NO) reduces ischemia/reperfusion injury in animal models and in patients. The objective of this study was to learn whether inhaled NO improves outcomes after CA and cardiopulmonary resuscitation (CPR).
Adult male mice were subjected to potassium-induced CA for 7.5 minutes whereupon CPR was performed with chest compression and mechanical ventilation. One hour after CPR, mice were extubated and breathed air alone or air supplemented with 40 ppm NO for 23 hours. Mice that were subjected to CA/CPR and breathed air exhibited a poor 10-day survival rate (4 of 13), depressed neurological and left ventricular function, and increased caspase-3 activation and inflammatory cytokine induction in the brain. Magnetic resonance imaging revealed brain regions with marked water diffusion abnormality 24 hours after CA/CPR in mice that breathed air. Breathing air supplemented with NO for 23 hours starting 1 hour after CPR attenuated neurological and left ventricular dysfunction 4 days after CA/CPR and markedly improved 10-day survival rate (11 of 13; P=0.003 versus mice breathing air). The protective effects of inhaled NO on the outcome after CA/CPR were associated with reduced water diffusion abnormality, caspase-3 activation, and cytokine induction in the brain and increased serum nitrate/nitrite levels. Deficiency of the α1 subunit of soluble guanylate cyclase, a primary target of NO, abrogated the ability of inhaled NO to improve outcomes after CA/CPR.
These results suggest that NO inhalation after CA and successful CPR improves outcome via soluble guanylate cyclase-dependent mechanisms.
[Show abstract][Hide abstract] ABSTRACT: Treatment with statins, inhibitors of HMG-CoA reductase, extends the survival of septic mice. However, the molecular mechanisms underlying the cholesterol-lowering, independent beneficial effects of statins in sepsis are poorly understood. The inhibition of protein isoprenylation, namely farnesylation and geranylgeranylation, has been proposed as a mediator of the pleiotropic protective effects of statins, although direct evidence is lacking. Major features of sepsis-induced immune suppression include T-cell dysfunction, which is characterized by apoptosis of splenic T cells, increased CD4(+)Foxp3(+) regulatory T cells (Tregs), and suppression of type 1 helper T-cell response [e.g., interferon-γ (IFN-γ) secretion] in mice. Here, we show that the induction of sepsis by cecal ligation and puncture (CLP) resulted in increases in farnesyltransferase activity and farnesylated proteins in the spleen relative to sham operation. Treatment with farnesyltransferase inhibitor N-[4-[2(R)-amino-3-mercaptopropyl]amino-2-phenylbenzoyl]methionine methyl ester trifluoroacetate salt (FTI-277) (25 mg/kg b.wt. i.p.) at 2 h after CLP blocked the increase in farnesylated proteins and improved survival and bacterial clearance of septic mice. FTI-277 reverted to or mitigated sepsis-induced apoptosis in spleen and thymus, increased splenic CD4(+)Foxp3(+) Tregs, and suppressed IFN-γ secretion and proliferation of splenocytes in response to anti-CD3+CD28 antibodies in mice. Moreover, FTI-277 promoted macrophage phagocytotic activity in septic mice. These results indicate that elevation in protein farnesylation plays a role in derangements in immune function and mortality of septic mice. These findings suggest that prevention of immune dysfunction might contribute to FTI-277-induced improvement in survival of septic mice. These data highlight protein farnesyltransferase as a novel potential molecular target to reduce the mortality of patients with sepsis.
Full-text · Article · Aug 2011 · Journal of Pharmacology and Experimental Therapeutics
[Show abstract][Hide abstract] ABSTRACT: Delayed paraplegia remains a devastating complication after ischemic spinal cord injury associated with aortic surgery and trauma. Although apoptosis has been implicated in the pathogenesis of delayed neurodegeneration, mechanisms responsible for the delayed paraplegia remain incompletely understood. The aim of this study was to elucidate the role of apoptosis in delayed motor neuron degeneration after spinal cord ischemia.
Mice were subjected to spinal cord ischemia induced by occlusion of the aortic arch and left subclavian artery for 5 or 9 minutes. Motor function in the hind limb was evaluated up to 72 hours after spinal cord ischemia. Histological studies were performed to detect caspase-3 activation, glial activation, and motor neuron survival in the serial spinal cord sections. To investigate the impact of caspase-3 activation on spinal cord ischemia, outcome of the spinal cord ischemia was examined in mice deficient for caspase-3.
In wild-type mice, 9 minutes of spinal cord ischemia caused immediate paraplegia, whereas 5 minutes of ischemia caused delayed paraplegia. Delayed paraplegia after 5 minutes of spinal cord ischemia was associated with histological evidence of caspase-3 activation, reactive astrogliosis, microglial activation, and motor neuron loss starting at approximately 24 to 48 hours after spinal cord ischemia. Caspase-3 deficiency prevented delayed paraplegia and motor neuron loss after 5 minutes of spinal cord ischemia, but not immediate paraplegia after 9 minutes of ischemia.
The present results suggest that caspase-3 activation is required for delayed paraplegia and motor neuron degeneration after spinal cord ischemia.
[Show abstract][Hide abstract] ABSTRACT: Although inhalation of 80 parts per million (ppm) of hydrogen sulfide (H2S) reduces metabolism in mice, doses higher than 200 ppm of H2S were required to depress metabolism in rats. We therefore hypothesized that higher concentrations of H2S are required to reduce metabolism in larger mammals and humans. To avoid the potential pulmonary toxicity of H2S inhalation at high concentrations, we investigated whether administering H2S via ventilation of an extracorporeal membrane lung (ECML) would provide means to manipulate the metabolic rate in sheep.
A partial venoarterial cardiopulmonary bypass was established in anesthetized, ventilated (fraction of inspired oxygen = 0.5) sheep. The ECML was alternately ventilated with air or air containing 100, 200, or 300 ppm H2S for intervals of 1 hour. Metabolic rate was estimated on the basis of total CO2 production (VCO2) and O2 consumption (VO2). Continuous hemodynamic monitoring was performed via indwelling femoral and pulmonary artery catheters.
VCO2, VO2, and cardiac output ranged within normal physiological limits when the ECML was ventilated with air and did not change after administration of up to 300 ppm H2S. Administration of 100, 200 and 300 ppm H2S increased pulmonary vascular resistance by 46, 52 and 141 dyn·s/cm5, respectively (all P ≤ 0.05 for air vs. 100, 200 and 300 ppm H2S, respectively), and mean pulmonary artery pressure by 4 mmHg (P ≤ 0.05), 3 mmHg (n.s.) and 11 mmHg (P ≤ 0.05), respectively, without changing pulmonary capillary wedge pressure or cardiac output. Exposure to 300 ppm H2S decreased systemic vascular resistance from 1,561 ± 553 to 870 ± 138 dyn·s/cm(5) (P ≤ 0.05) and mean arterial pressure from 121 ± 15 mmHg to 66 ± 11 mmHg (P ≤ 0.05). In addition, exposure to 300 ppm H2S impaired arterial oxygenation (PaO2 114 ± 36 mmHg with air vs. 83 ± 23 mmHg with H2S; P ≤ 0.05).
Administration of up to 300 ppm H2S via ventilation of an extracorporeal membrane lung does not reduce VCO2 and VO2, but causes dose-dependent pulmonary vasoconstriction and systemic vasodilation. These results suggest that administration of high concentrations of H2S in venoarterial cardiopulmonary bypass circulation does not reduce metabolism in anesthetized sheep but confers systemic and pulmonary vasomotor effects.
Full-text · Article · Feb 2011 · Critical care (London, England)
[Show abstract][Hide abstract] ABSTRACT: Parkinson's disease is one of the major neurodegenerative disorders. Neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) can cause Parkinson's disease-like symptoms and biochemical changes in humans and animals. Hydrogen sulfide (H(2)S) has been shown to protect neurons. The goal of this study was to examine the effects of inhaled H(2)S in a mouse model of Parkinson's disease induced by MPTP. Male C57BL/6J mice received MPTP at 80 mg/kg and breathed air with or without 40 ppm H(2)S for 8 h/day for 7 days. Administration of MPTP induced movement disorder and decreased tyrosine hydroxylase (TH)-containing neurons in the substantia nigra and striatum in mice that breathed air. Inhalation of H(2)S prevented the MPTP-induced movement disorder and the degeneration of TH-containing neurons. Inhaled H(2)S also prevented apoptosis of the TH-containing neurons and gliosis in nigrostriatal region after administration of MPTP. The neuroprotective effect of inhaled H(2)S after MPTP administration was associated with upregulation of genes encoding antioxidant proteins, including heme oxygenase-1 and glutamate-cysteine ligase. These observations suggest that inhaled H(2)S prevents neurodegeneration in a mouse model of Parkinson's disease induced by MPTP, potentially via upregulation of antioxidant defense mechanisms and inhibition of inflammation and apoptosis in the brain.
[Show abstract][Hide abstract] ABSTRACT: The development of Parkinson's disease is accompanied by concurrent activation of caspase-3 and apoptosis of dopaminergic neurons of human patients and rodent models. The role of caspase-3, a final executioner of apoptosis, in the pathogenesis of Parkinson's disease, however, remains to be determined. Here, we show that gene disruption of caspase-3 protects mice from 1-methyle-4-phenyl-1,2,3,6-tetrahmydropyridine (MPTP)-induced Parkinsonian syndrome, as reflected by reversal of MPTP-induced bradykinesia and decreased tyrosine hydroxylase expression in the nigra-striatum. MPTP treatment resulted in increased caspase-3 activation and apoptosis in the substantia nigra of wild-type mice at 24 h after the inception of MPTP treatment, as compared with vehicle-treated control animals. Gene disruption of caspase-3 prevented MPTP-induced apoptosis in the substantia nigra. At 7 days after MPTP treatment, tyrosine hydroxylase expression was suppressed and infiltration of activated microglia and astrocytes was markedly increased in the nigra-striatum of wild-type mice. All of these alterations following MPTP treatment were blocked by disruption of caspase-3 in mice. These results clearly indicate that caspase-3 activation is required for the development of MPTP-induced Parkinson's disease in mice. These findings suggest that activation of caspase-3-mediated apoptosis of dopaminergic neurons in the early stage may play an important role in the pathogenesis of Parkinson's disease.
Full-text · Article · Oct 2010 · Biochemical and Biophysical Research Communications
[Show abstract][Hide abstract] ABSTRACT: NO has been implicated in the pathogenesis of septic shock. However, the role of NO synthase 3 (NOS3) during sepsis remains incompletely understood. Here, we examined the impact of NOS3 deficiency on systemic inflammation and myocardial dysfunction during peritonitis-induced polymicrobial sepsis. Severe polymicrobial sepsis was induced by colon ascendens stent peritonitis (CASP) in wild-type (WT) and NOS3-deficient (NOS3KO) mice. NOS3KO mice exhibited shorter survival time than did WT mice after CASP. NOS3 deficiency worsened systemic inflammation assessed by the expression of inflammatory cytokines in the lung, liver, and heart. Colon ascendens stent peritonitis markedly increased the number of leukocyte infiltrating the liver and heart in NOS3KO but not in WT mice. The exaggerated systemic inflammation in septic NOS3KO mice was associated with more marked myocardial dysfunction than in WT mice 22 h after CASP. The detrimental effects of NOS3 deficiency on myocardial function after CASP seem to be caused by impaired Ca handling of cardiomyocytes. The impaired Ca handling of cardiomyocytes isolated from NOS3KO mice subjected to CASP was associated with depressed mitochondrial ATP production, a determinant of the Ca cycling capacity of sarcoplasmic reticulum Ca-ATPase. The NOS3 deficiency-induced impairment of the ability of mitochondria to produce ATP after CASP was at least in part attributable to reduction in mitochondrial respiratory chain complex I activity. These observations suggest that NOS3 protects against systemic inflammation and myocardial dysfunction after peritonitis-induced polymicrobial sepsis in mice.
No preview · Article · Dec 2009 · Shock (Augusta, Ga.)