[Show abstract][Hide abstract] ABSTRACT: Any perturbation in the normal functioning of endoplasmic reticulum (ER), such as due to hypoxia, triggers the unfolded protein response (UPR). We studied the temporal variation in gene expression in murine kidney exposed to acute hypobaric hypoxia. Molecular chaperones like Grp78, Grp94, Canx and Calr in the ER were transcriptionally downregulated. Further, the splicing of Xbp1 mRNA decreased, whereas transcription of the unspliced mRNA increased. This step produces Xbp1 protein, which is negatively regulated by the unspliced protein. Hence, the decreased splicing of Xbp1 along with decreased transcription of ER chaperones in kidney is a definite indication of reduced stress.
[Show abstract][Hide abstract] ABSTRACT: Our previous study showed that YGGFMKKKFMRFamide (YFa), a chimeric peptide of Met-enkephalin, and Phe-Met-Arg-Phe-NH2 induced naloxone-reversible antinociception and attenuated the development of tolerance to morphine analgesia. In continuation, the present study investigated which specific opioid receptors-mu, delta or kappa-mediate the observed YFa antinociception pharmacologically using specific antagonists and whether chronic administration of YFa at 26.01 micromol/kg per day induces tolerance and its effect on the expression of mu and kappa opioid receptors from day 4 to day 6, with endomorphine-1 (EM-1) and saline taken as positive and negative controls, respectively. Quantitative differential expression analysis was carried out by real-time reverse-transcriptase polymerase chain reaction, and the corresponding changes in protein levels were assessed by Western blot. A pharmacological investigation revealed that nor-binaltorphimine, a specific kappa opioid receptor-1 (KOR1) antagonist, completely antagonized the antinociception induced by 39.01 micromol/kg of YFa. Importantly, its chronic intraperitoneal administration did not result in significant tolerance over 6 days, whereas EM-1 induced significant tolerance after day 4. Differential expression analysis revealed that EM-1 caused up-regulation of mu opioid receptor-1 on day 4, followed by down-regulation on later days. Interestingly, YFa treatment caused a decrease on day 4, followed by an increase in the expression of KOR1 from day 5 onward. In conclusion, YFa induces kappa-specific antinociception, with no development of tolerance during 6 days of chronic treatment, which further articulates new directions for improved designing of peptide-based analgesics that may be devoid of adverse effects like tolerance.
No preview · Article · May 2008 · Journal of Neuroscience Research
[Show abstract][Hide abstract] ABSTRACT: Under hypobaric hypoxia, antioxidant defenses of the heart are stressed by the enhanced production of ROS. Mammalian heart acclimatizes to hypoxia through altered gene expression, which we studied in murine heart exposed to 10h of acute hypobaric hypoxia (AHH), equivalent to 15000ft, using cDNA arrays. Functional classification of genes with a > or =2-fold change revealed a number of pro-oxidants like Cyba, Xdh, Txnip, Ppp1r15b and antioxidants like Cat, Gpx1, Mt1, Mgst1. Interestingly, the protein level of Cyba, a subunit of NADPH oxidase, was markedly decreased in AHH exposed heart, suggesting the involvement of some stress response pathways. The AHH exposure also caused a significant reduction (50%) in the level of GSH (P<0.05). The present study provides a retrospective insight on the cellular antioxidant defense mechanisms under AHH.
[Show abstract][Hide abstract] ABSTRACT: Ascent to high-altitude results in decreased inspired partial pressure of oxygen because of a decrease in barometric pressure. Altitude acclimatization requires physiological and metabolic changes to improve tolerance to altitude hypoxia. Cellular response to hypoxia results into changes in the profile of gene expression and the present study explored the same in murine model. Liver being the largest metabolic organ, the molecular details of acute hypobaric hypoxia (AHH) induced transcriptional changes in the tissue were investigated. Swiss albino mice were exposed to hypobaric hypoxia ( approximately 426mmHg) in a decompression chamber and cDNA microarray was used to study the transcriptional profile in liver. Notably, by the tenth hour several of the genes involved in sterol metabolism such as SREBF1, INSIG1, HMGCS1, FDFT1, SQLE, and HSD3B4 were downregulated more than 2-fold suggesting that AHH suppresses sterol biosynthesis in the liver. Real-time PCR helped validate the downregulation of SREBF1, HMGCS1, FDFT1, and HSD3B4 genes. However, no significant change was observed in the serum cholesterol levels throughout the AHH exposure. The findings are indicative of transcriptional downregulation of SREBP target genes as a part of acclimatization response to hypoxia. The study highlights the significance of SREBP in the regulation of sterol metabolism under the acute hypoxic response.
Full-text · Article · Apr 2007 · Biochemical and Biophysical Research Communications
[Show abstract][Hide abstract] ABSTRACT: Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric basic-helix-loop-helix-PER-ARNT-SIM (bHLH-PAS) transcription factor consisting of HIF-1alpha and HIF-1beta subunits. HIF-1alpha is the oxygen-regulated subunit of HIF-1, which regulates the transcription of genes involved in oxygen homeostasis in response to hypoxia. Yak (Bos grunniens), a mammal native to high altitude (HA) region ( approximately 3500-5500 m), has successfully adapted over many generations to the chronic hypoxia of HA. In the present work, cDNA encoding HIF-1alpha has been cloned from the blood of yak. Tissue specific expression of the mRNA was analyzed in blood, heart, lung, liver and kidney by RT-PCR with primers from three different regions of cDNA. The HIF-1alpha expression was liver and blood specific. The HIF-1alpha mRNA contains 823 bp long 3'UTR that is AU-rich and contains ten AUUUA pentamers and two overlapping copies of the nonamer UUAUUUAUUUAUU. Three potential microRNAs, hsa-miR-107/mmu-miR-107/rno-miR-107, hsa-miR-18b and hsa-miR-135a/mmu-miR-135a/rno-miR-135a, targeting 3'UTR of yak HIF-1alpha, were identified by using target prediction software. The CDS encodes for 823 residues of amino acids and showed 99%, 95%, 92%, 90% and 90% similarity to domestic cattle, human, plateau pika, mouse and rat HIF-1alpha, respectively. HIF-1alpha cDNA, cloned and sequenced in the present work has revealed the evolutionary conservation through multiple sequence alignment. Liver and blood specific stability of HIF-1alpha mRNA appears miR-107 regulated.