Involvement of ObRb receptor, nitric oxide, and BKCa channel signaling pathways in leptin-induced relaxation of pregnant mouse uterus.

The purpose of this study was to determine the receptor subtype and the underlying mechanisms involved in the relaxant effect to leptin in mid- and late-pregnant mouse uterus. We determined the relative mRNA expression of receptor subtypes, eNOS, and BKCa channel by quantitative PCR and also the overall receptor expression by immunohistochemistry. Isometric tension studies were conducted to evaluate the effects of leptin and to delineate its mechanisms. A selective siRNA for the ObRb receptor was used to determine the participation of the receptor subtype in biochemical and molecular effects of leptin. The relaxant response to leptin was greater in mid-pregnancy compared to late pregnancy and was mediated by the activation of BKCa channels by eNOS-derived nitric oxide in an ObRb receptor-dependent manner. In comparison to mid-pregnancy, expression of short forms (mainly ObRa receptor) of the receptor was significantly increased in late pregnancy, whereas ObRb receptor expression was similar in both phases. The results of the study suggest that ObRb receptor mediates leptin-induced increase in eNOS expression and NO synthesis. Leptin-induced eNOS expression and activation cause cGMP-independent stimulation of BKCa channels causing uterine relaxation. Increased short forms of the receptors and reduced BKCa channels exert a negative effect on uterine relaxation in late pregnancy. Leptin may have a physiological role in maintaining uterine quiescence in mid-pregnancy and its reduced relaxant response in late gestation may facilitate labor. Further, ObRb receptor agonists may be useful in the management of preterm labor.

Experimental safety testing confirms that the NSAID nimesulide is toxic to Gyps vultures in India.

Population declines of Gyps vultures throughout South Asia were caused by unintentional poisoning by the NSAID diclofenac, which was subsequently banned. However, other vulture-toxic NSAIDs are available, including nimesulide, which, in experiments carried out in South Africa, was shown to be toxic to Gyps vultures. We report on safety-testing of nimesulide carried out on Himalayan Griffons G. himalayensis. We gave two vultures a dose of nimesulide by oral gavage at the maximum level of exposure, with two controls dosed with benzyl alcohol. In the two tested birds, plasma nimesulide concentrations peaked after six hours, while serum uric acid concentrations increased steadily up until 24 h post-treatment, after which both birds died, displaying severe visceral gout. The control birds showed no adverse clinical or biochemical signs. We confirm that nimesulide is toxic to Gyps vultures. Veterinary use of nimesulide should be banned in all Gyps vulture range countries in the region.

PRE-084 ameliorated kidney injury by reducing endoplasmic reticulum stress in the rat model of adenine-induced chronic kidney disease.

BACKGROUND: Endoplasmic reticulum (ER) stress plays an important role in the development of chronic kidney disease (CKD). Sigma-1 receptors (σ1Rs) are novel chaperone proteins that regulate ER stress. However, effect of σ1R activation on renal ER stress is yet unexplored. So, in the present study we investigated the effects of PRE-084, a σ1R agonist on renal injury and ER stress in the rat model of CKD. METHODS: CKD group rats were fed adenine for 28 days and CKD treatment group rats were additionally administered PRE-084 intraperitoneally at 1, 3 and 10 mg/kg body weight dose from Day 22-28. ER stress markers were evaluated using molecular biology techniques such as immunohistochemistry and Western blot. RESULTS: Marked kidney injury was observed in CKD rats as revealed by biochemical and histological findings. Expression of ER stress proteins such as phosphorylated protein kinase R-like ER kinase (p-PERK), cleaved activating transcription factor-6 (ATF-6f), phosphorylated inositol requiring enzyme1α (p-IRE1α) and caspase-12 were higher in CKD rats. Nevertheless, CKD rats treated with PRE-084 particularly at 10 mg/kg dose showed considerably lesser kidney injury along with higher expression of σ1R and marked reduction of all the ER stress proteins studied. CONCLUSION: Results reveal that PRE-084 likely ameliorated the adenine-induced kidney injury by lowering ER stress through increased σ1R expression.

Fat augments leptin-induced uterine contractions by decreasing JAK2 and BKCa channel expressions in late pregnant rats.

Altered lipid metabolism in obesity causes pregnancy complications in humans and animals. Leptin levels increase in pregnancy, as well as obesity. However, the effect of obesity on uterine leptin receptors and its distal signaling is not clear. The present study aimed to understand the effect of increased fat on leptin signaling in rat uterus. Wistar female rats were fed with an HF diet (40% Fat, 17% Sucrose, 1.25% Cholesterol, 0.75% Cholic acid) for 6 weeks before the mating and during pregnancy. HF diet significantly increased the fat depots, liver weight, serum, and tissue cholesterol levels. It produced fatty degeneration in the liver and caused infiltration of inflammatory cells, cystic endometrial glands, and sub endometrial fibrosis of the uterus. In isometric tension experiments, leptin caused a significant increase in uterine contractions in high fat-fed animals compared to control animals. Analysis of receptor expressions revealed no significant difference between the groups. However, a significant decrease in the JAK2 and BKCaα mRNA expression was observed in the uterus of high fat-fed rats. No change in the BKCaß, eNOS, iNOS, MLCP, and MLCK mRNA expressions was noticed in the HF group compared to the control. The findings of the present study suggest that the contractile response to leptin in the uterus of high fat-fed rats may be attributed to reduced signaling through JAK2 and, lowered expressions of BKCa channel α subunits.

Impact of heat stress on broilers with varying body weights: Elucidating their interactive role through physiological signatures.

Physiological determinants of different body weight (BW) broiler chickens under heat stressed conditions were investigated to compare the performance at market age considering medium body weight group as standard. At 5 weeks, broilers were categorized randomly into 3 treatments (N = 24 per group) as high (HBW) (>1050 g), medium (MBW) (900-1050 g) and low (LBW) (<900 g) followed by simultaneous exposure to normal and heat stress (HS) conditions at 40 ± 1 °C and 45 ± 5% RH for 4 h/day for a period of 7 days (D) and sample collection was employed at D0, D3 and D7. Physiological and stress responses, haematological and biochemical profile, intestinal gross and histological aspects were estimated using standard protocols. Heart rate and mean arterial blood pressure were significantly (P = 0.000) higher in HBW broilers followed by low and medium ones. Heat stress exposure indicated significant (P = 0.000) increase in heart rate, arterial blood pressure, respiration rate and comb temperature while cloacal temperature remained unaffected. Lymphocytes, eosinophils, total red blood cell count, haemoglobin, and haematocrit were reduced (P = 0.000) whereas mean corpuscular volume and mean corpuscular hemoglobin, heterophil count and heterophil to lymphocyte ratio were increased (P = 0.000) in response to HS. Circulating corticosterone and tri-iodothyronine concentrations showed inverse relationship with respect to BW variation and HS duration respectively with significant interaction (P = 0.000). Higher protein in LBW was observed on D3. Serum triglycerides remained unaffected till D3 exposure but significantly (P = 0.017) reduced on D7 with lowest content in HBW group. Serum alkaline phosphatase increased in LBW group with significant heat stress interaction (P = 0.000) on D3. HS reduced villi length and crypt depth; but their corresponding ratio increased. In conclusion, HBW broilers are more affected than MBW or LBW groups. This study established interactive roles of BW and HS on physiological responses in broilers.

Leptin receptor stimulation in late pregnant mouse uterine tissue inhibits spontaneous contractions by increasing NO and cGMP.

The adipokine, leptin exerts inhibitory effect on both spontaneous and oxytocin-induced contractions in myometrium. However, the mechanisms involved in leptin-induced effect are not clear. In the present study, we studied the altered characteristics of uterine contractions in the presence of leptin and the possible mechanisms of its effect in late pregnant (18.5 day) mouse uterus. We conducted functional, biochemical and molecular biology studies to demonstrate the mechanism of leptin-induced response. Leptin exerted an inhibitory response (Emax 40.5 ± 3.99%) on basal uterine contractions. The extent of inhibition was less than that obtained with known uterine relaxants, salbutamol (Emax103 ± 8.66%) and BRL-37344 (Emax 84.79 ± 8.12%). Leptin-induced uterine response was inhibited by leptin receptor antagonist SHLA and JAK-STAT pathway inhibitor, AG-490. The relaxant response was also subdued by NO-cGMP-PK-G pathway blockers L-NAME, 1400W, ODQ and KT-5823. Further, leptin enhanced the levels of NO and cGMP in uterine tissues. Also, SHLA, AG-490 and a combination of 1400 W and L-NAME prevented leptin-induced increase in NO. Similar effect was observed on cGMP levels in presence of leptin and SHLA. However, leptin did not influence CaCl2-induced response in potassium-depolarized tissues. We also detected leptin receptor protein in late pregnant mouse uterus located in endometrial luminal epithelium and myometrial layers. Real-time PCR studies revealed significantly higher expression of short forms of the receptor (ObRa and ObRc) in comparison to the long form (ObRb). In conclusion, the results of the present study suggest that leptin inhibits mouse uterine contraction by stimulating short forms of the leptin receptors and activating NO pathway in a JAK-STAT-dependent manner.