Differential expression of sirtuin 2 and adipocyte maturation restriction: an adaptation process during hypoxia in fish.

Sirtuins have received widespread attention due to their diverse physiological role in metabolism. Among sirtuins, SIRT2 is more abundant in adipocytes and exerts effects on adipocyte differentiation, a process which involves conversion of preadipocytes to mature adipocytes orchestrated by adipokines and adipogenic transcription factors. Grey mullet (Mugil cephalus) was chosen as a study organism due to its excellent service as a biomonitor. Adipocytes isolated from natural field conditions were termed as field-hypoxic (Ennore) and -normoxic (Kovalam) based on dissolved oxygen (DO) level in the estuary. A previous study portrayed the hypoxic instance of Ennore estuary (low DO) and grey mullet [HIF1α in adipocytes, brain endothelial cell (EC) and hepatocytes] inhabiting this estuary ( Padmini et al., 2016a, b; Padmini and Tharani, 2015). In this context, fish adipocytes of both conditions were subjected to in vitro hypoxia for 1 h (in the pre/trigassed incubator with the supply of 1% O2; 94% N2; 5% CO2) and were analysed for the expression of adipokines, adipogenic transcription factors and anti-adipogenic markers in fish adipocytes. Elevation of asymmetric dimethylarginine (ADMA), TNFα and leptin along with decreased adiponectin, adipogenic transcription factors and altering sirtuins were observed in test adipocytes and in control adipocytes on in vitro hypoxia. This suggests that adipocytes may follow internal caloric restriction as portrayed from cytomorphological/ultrastructural analysis, limiting adipocyte maturation process, one of the adaptive mechanisms triggered by adipocyte of fish surviving in Ennore estuary. Prolonged exposure to hypoxia (test on in vitro hypoxia for 1 h) showed a drastic alteration in these components leading to both structural and biological fluctuation when compared to limited hypoxic condition (field-hypoxic and control on in vitro hypoxia). Our study concludes that hypoxia may serve as the chief molecular cue in eliciting adipocyte maturation restriction though metabolic reprogramming and it also shows the significance of adipocyte maturation restriction in imparting survival mechanism.

Differential expression of survival proteins during decreased intracellular oxygen tension in brain endothelial cells of grey mullets.

The brain requires constant oxygen supply to perform its biological functions essential for survival. Because of low oxygen capacity and poor oxygen diffusibility of water, many fish species have evolved various adaptive mechanisms to cope with depleted oxygen. Endothelial cells (EC) are the primary components responsible for controlled environment of brain. Brain homeostasis largely depends on integrity of the EC. To elucidate their adaptive strategy, EC were isolated from the fish brain of Kovalam-control site and Ennore estuary-test/field hypoxic site and were subjected to low oxygen tension in laboratory. Cell viability, 4-hydroxynonenal (4HNE) and total antioxidant capacity (TAC) were analyzed to ascertain stress. Hypoxic insult, cytoprotective role of HSPs and apoptotic effect were analyzed by assessing hypoxia-inducible-factor-α (HIF1α), heat-shock-protein-70 (HSP70), heme-oxygenase 1 (HO-1), and apoptosis signal regulating kinase-1 (ASK1). This study evidenced that HSP70 and HO-1 are the key stress proteins, confer high tolerance to decreased oxygen tension mediated stress.

Genistein attenuates oxidative damage in preeclamptic placental trophoblast.

OBJECTIVE: To evaluate the effect of genistein supplementation on the oxidative/nitrative stress and antioxidant capacity of normotensive and preeclamptic placental trophoblast. METHODS: The stress status of placental trophoblast was assessed by measuring their respective markers before and after incubation with genistein. RESULTS: A significant increase in stress along with decrease in antioxidant status was observed in preeclamptic placental trophoblast, whereas genistein incubation significantly alters oxidant-antioxidant status. CONCLUSION: The study revealed that genistein may play a significant role in controlling oxidative/nitrative stress during preeclampsia. Hence, genistein can be used as an effective dietary supplement for the treatment and management of preeclampsia.

Differential regulation of pro- and antiapoptotic proteins in fish adipocytes during hypoxic conditions.

Worldwide, the frequencies and magnitudes of hypoxic events in estuarine waters have increased considerably over the past two decades. Fish populations are suitable indicators for the assessment of quality of aquatic ecosystems and often comprise a variety of adaptation systems by triggering oxidants, antioxidants and hypoxia-responsive signaling proteins. Signaling pathway may lead to cell survival or cell death which is fine-tuned by both positive and negative factors, which includes hypoxia-inducible factor-1α (HIF1α), heat-shock protein-70 (HSP70), phospho-c-Jun N-terminal kinase 1/2 (p-JNK1/2) and apoptosis signal-regulating kinase-1 (ASK1). In the present study, we attempt to determine stress-mediated signaling changes and molecular mechanism behind the cell survival by comparing adipocytes of fish from field hypoxic condition and laboratory-induced hypoxic condition (in vitro hypoxia). Comparison of field and laboratory studies in fish adipocytes showed differential expression of HIF1α, HSP70, p-JNK1/2 and ASK1 with altered oxidants and antioxidants. Further, the results also suggest that in vitro hypoxic conditions mimic field hypoxic conditions. Trends of hypoxia response were same in in vitro hypoxia of control adipocytes as in Ennore estuary, and hypoxia response was more pronounced in the test adipocytes under in vitro hypoxic condition. Results of the present work suggest that hypoxia is the major crusade of water pollutants affecting fish by differential regulation of pro- and antiapoptotic proteins probably through HSP70. This may play a vital role by providing cytoprotection in pollutant-induced stressed fish adipocytes substantiated by the in vitro hypoxic studies.

Differential expression of HSP90α and heme oxygenase in cord blood RBC during preeclampsia.

Preeclampsia is a multisystem disorder with profound implications on both mother and fetus. Analysis of umbilical cord blood red blood cell (RBC) changes shall depict the fetal response to pregnancy-specific complications like preeclampsia. This study aims to analyze the regulation relationship between HSP90α and heme oxygenase-2 (HO-2) in cord blood RBC during preeclampsia. The lipid hydroperoxide (LHP) and 3-nitrotyrosine (3-NT) levels were measured as stress markers in cord blood RBC of both subjects. The impact of stress on RBC was assessed by measuring the level of membrane bound enzymes and assessing the changes in cord blood RBC. The expression of HSP90α and HO-2 were analyzed by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry analysis, respectively. There was significant increase in the level of LHP (p < 0.01), 3-NT (p < 0.05), HSP90α (p < 0.01) with decrease in the expression of HO-2 (p < 0.05) in cord blood RBC of preeclamptic subjects compared to normotensive subjects. Similarly, the membrane damage in preeclamptic RBC was assessed by spectrophotometrically and found to be increased by 41.7%, along with increase in number of nucleated RBC. The antiproliferative effect of carbon monoxide under stress might decrease the expression of HO-2 under conditions when there is an increasing need for RBC. The role of HSP90α level in cord blood RBC is discussed with reference to nitrative stress in preeclampsia. This study concludes the increased expression of nucleated RBC, HSP90α and corresponding decreased expression of HO-2 in such hypoxic condition may play a protective role; to prevent cord blood RBC against stress induced damage during preeclampsia.

HSP70 expression and its role in preeclamptic stress.

Preeclampsia, a hypertensive pregnancy-specific disorder, has long been analyzed for its association with cellular stress. It still remains one of the most serious complications of pregnancy. It is a multi-system disorder that affects maternal vascular function and fetal growth. The physiopathology of preeclampsia is still unclear, but an imbalance between reactive oxygen species (ROS) and antioxidants, appears to be an important contributing factor. Oxidative stress has been increasingly postulated as a major contributor to endothelial dysfunction in preeclampsia (PE). The ROS promotes lipid oxidation and are known to induce stress proteins, such as hemeoxygenase 1 (HO-1) and heat-shock protein 70 (HSP70). Embryonic and placental cells are highly sensitive to oxidative stress due to their proliferate nature. Endothelial cell dysfunction is suggested to be a part of wider maternal inflammatory reaction responsible for the clinical syndrome of preeclampsia. Part of the dysfunction in endothelial cell and trophoblast is attributed to oxidative stress developed during pregnancy. The disequilibrium in compensatory antioxidant control is proposed as a causative mechanism in the pathophysiology of preeclampsia. HSP70 acts as the secondary line of defense in systems with compromised antioxidant function. This article reviews the differential expression of HSP70 and the effect of mint-tea therapy to modulate preeclamptic oxidative damage.