Water deprivation-induced hypoxia and oxidative stress physiology responses in respiratory organs of the Indian stinging fish in near coastal zones

Background

Water deprivation-induced hypoxia stress (WDIHS) has been extensively investigated in numerous fish species due to their adaptation with accessory respiratory organs to respire air but this has not been studied in Indian stinging fish Heteropneustes fossilis. Data regarding WDIHS-induced metabolism in accessory respiratory organ (ARO) and gills and its relationship with oxidative stress (OS) in respiratory organs of air-breathing fish H. fossilis, are limited. So, this study aimed to investigate the effects of WDIHS (0, 3, 6, 12, and 18 h) on hydrogen peroxide (H2O2) as reactive oxygen species (ROS), OS, redox regulatory enzymes, and electron transport enzymes (ETC) in ARO and gills of H. fossilis.

Methods

Fish were exposed to air for different hours (up to 18 h) against an appropriate control, and ARO and gills were sampled. The levels of oxygen saturation in the body of the fish were assessed at various intervals during exposure to air. Protein carbonylation (PC) and thiobarbituric acid reactive substances (TBARS) were used as OS markers, H2O2 as ROS marker, and various enzymatic activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), along with the assessment of complex enzymes (I, II, III, and V) as well as the levels of ascorbic acid (AA) and the reduced glutathione (GSH) were quantified in both the tissues.

Results

Discriminant function analyses indicate a clear separation of the variables as a function of the studied parameters. The gills exhibited higher levels of GSH and H2O2 compared to ARO, while ARO showed elevated levels of PC, TBARS, AA, SOD, CAT, and GPx activities compared to the gills. The activities of GR and ETC enzymes exhibited similar levels in both the respiratory organs, namely the gills, and ARO. These organs experienced OS due to increased H2O2, TBARS, and PC levels, as observed during WDIHS. Under WDIHS conditions, the activity/level of CAT, GPx, GR, and GSH decreased in ARO, while SOD activity, along with GR, GSH, and AA levels decreased in gills. However, the activity/level of SOD and AA in ARO and CAT in gills was elevated under WDIHS. Complex II exhibited a positive correlation with WDIHS, while the other ETC enzymes (complex I, III, and V) activities had negative correlations with the WDIHS.

Discussion

The finding suggests that ARO is more susceptible to OS than gills under WDIHS. Despite both organs employ distinct redox regulatory systems to counteract this stress, their effectiveness is hampered by the inadequacy of small redox regulatory molecules and the compromised activity of the ETC, impeding their ability to effectively alleviate the stress induced by the water-deprivation condition.

Spatio-temporal changes in oxidative stress physiology parameters in apple snail Pila globosa as a function of soil Mg, Ca, organic carbon and aquatic physico-chemical factors

Information on the oxidative stress physiology parameters (OSPP) in general and as a function of the fluctuation of Mg, Ca and organic carbon present in soil and aquatic physico-chemical factors such as pH, temperature and salinity in particular are scanty in the amphibious snail Pila globosa. A spatio-temporal analysis of redox metabolism (as OSPP) followed by discriminant function analysis of the obtained data were performed in P. globosa sampled from the east-coasts of Odisha state, India (mostly along the Bay of Bengal) for environmental health assessment purposes. Results revealed that the OSPP are susceptible to seasonal synergistic variation of soil and physico-chemical factors. Overall, lipid peroxidation, total antioxidant capacity, activities of catalase, glutathione reductase had positive correlation whereas ascorbic acid, the reduced glutathione and the activity of superoxide dismutase had non-significant correlation with the soil Mg, Ca, organic carbon, and pH, temperature and salinity of water. In the summer season, the snails had a marked 51.83% and 26.41% higher lipid peroxidation level and total antioxidative activity as compared to the other seasons. Spatial variation of OSPP indicates that snails residing away from the Bay of Bengal coast had at least 4.4% lower antioxidant level in winter and 30% higher lipid peroxide levels in summer as compared to the rest of the sampling sites. Results on OSPP in P. globosa may be useful for monitoring the ecotoxic effects of environment using molluscs in general and P. globosa in particular.

Changes in physicochemical, heavy metals and air quality linked to spot Aplocheilus panchax along Mahanadi industrial belt of India under COVID-19-induced lockdowns

Positive effects of COVID-19-induced lockdowns on environment are well documented although pre-planned experiments for such analyses and appearance of fish species are lacking. We hypothesize that spotting the fish Aplocheilus panchax along the industrial belt of Mahanadi River near Cuttack in a never seen manner could be due to the regenerated environment. Heavy metals, water and air qualities along with spotting A. panchax in up, mid and downstream of Mahanadi River near Jagatpur industrial basins were analysed during pre-(end of March 2020) and after 60 days of lockdowns (last week of May 2020). An overall 45, 61, 79, 100, 97 and 90% reduction of Fe, Cu, Ni, Cd, Pb and Zn was recorded in the studied area after lockdowns, respectively. Similarly, dissolved oxygen and pH were elevated by 26 and 7%, respectively. Water temperature, conductivity and total dissolved solute levels were reduced by 7, 46 and 15%, respectively, which were again elevated during post-lockdowns during 2021 as observed from the Landsat-8 OLI satellite data. Air NO₂, SO₂, NH₃, PM_2.5, PM₁₀ and CO levels were alleviated by 58.75, 80.33, 72.22, 76.28, 77.33 and 80.15%, respectively. Finally, for the first time, about 12 A. panchax fish per 100 m shore line in the area were spotted. The observed lockdown-induced environmental healing at the studied area could contribute to the appearance of A. panchax in the study site and therefore a stringent environmental audit is suggested during post-COVID-19 periods to make the regenerated environmental status long lasting in such habitats.

Dehydration induced hypoxia and its role on mitochondrial respiratory enzymes and oxidative stress responses in liver of Asian stinging catfish Heteropneustes fossilis

In the present study, Water Deprived Condition (WPC, up to 18 h) induced hypoxia and altered oxidative stress (OS) physiology along with responses of respiratory chain enzyme in Heteropneustes fossilis are described . The body O₂ saturation level in the fish was declined with respect to air exposure. Higher levels of lipid peroxidation and protein carbonylation were recorded in the tissue of fish exposed to 6 h of WPC stress. The regulation of the mitochondrial complex and antioxidant enzymes, small antioxidant molecules indicated that the fish can moderately survive up to 6 h of air exposure. Probably with the onset of metabolic depression, it can critically resist the dehydration stress up to 18 h. Although the activities of glutathione peroxidase and reductase were elevated, activities of antioxidant enzymes such as superoxide dismutase and catalase were insufficient to combat WPC induced ROS and OS generated under hypoxia. The small antioxidant molecules played a key role in elimination of ROS. The elevated complex II activity was probably responsible for resisting the complex I, II and IV mediated electron leakage events in mitochondria of the fish under WPC. The total H₂O₂ removing capacity was less under WPC while the total units of all calculated antioxidants were alleviated signifying an interesting mechanism of WPC induced OS in the fish.

A detailed review of the outbreak of COVID-19

The disease COVID-19 caused by SARS-CoV-2 is the third highly infectious human Coronavirus epidemic in the 21^s⁢t century due to its high transmission rate and quick evolution of its pathogenicity. Genomic studies indicate that it is zoonotic from bats. The COVID-19 has led to significant loss of lives and a tremendous economic decline in the world. Generally, the population at risk of a fatal outcome are the elderly and those who are debilitated or are immune compromised. The fatality rate is high, but now is reduced after the development of preventive vaccine although an effective treatment by drug against the virus is yet to be developed. The treatment is narrowed to the use of several anti-viral drugs, or other re-purposed drugs. Social distancing, therefore, has emerged as a putative method to decrease the rate of infection. In this review, we summarize the aspects of the disease that is so far have come to light and review the impact of the infection on our society, healthcare, economy, education, and environment.

Modulation of physiological oxidative stress and antioxidant status by abiotic factors especially salinity in aquatic organisms

Exposure to a variety of environmental factors such as temperature, pH, oxygen and salinity may influence the oxidative status in aquatic organisms. The present review article focuses on the modulation of oxidative stress with reference to the generation of reactive oxygen species (ROS) in aquatic animals from different phyla. The focus of the review article is to explore the plausible mechanisms of physiological changes occurring in aquatic animals due to altered salinity in terms of oxidative stress. Apart from the seasonal variations in salinity, global warming and anthropogenic activities have also been found to influence oxidative health status of aquatic organisms. These effects are discussed with an objective to develop precautionary measures to protect the diversity of aquatic species with sustainable conservation. Comparative analyses among different aquatic species suggest that salinity alone or in combination with other abiotic factors are intricately associated with modulation in oxidative stress in a species-specific manner in aquatic animals. Osmoregulation under salinity stress in relation to energy demand and supply are also discussed. The literature survey of >50 years (1960-2020) indicates that oxidative stress status and comparative analysis of redox modulation have evolved from the analysis of various biotic and/or abiotic factors to the study of cellular signalling pathways in these aquatic organisms.