Physiological and behavioural responses to acid and osmotic stress and effects of Mucuna extract in Guppies

Effects of salinity stress on antioxidant status and inflammatory responses in females of a "Near Threatened" economically important fish species Notopterus chitala: a mechanistic approach

In the present study, acute stress responses of adult female Notopterus chitala were scrutinized by antioxidant status and inflammation reaction in the gill and liver at five different salinity exposures (0, 3, 6, 9, 12 ppt). Oxidative defense was assessed by determining superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase, and glutathione reductase activities, while malondialdehyde (MDA), glutathione, and xanthine oxidase levels were determined as indicators of oxidative load. Pro-inflammatory cytokines (IL-1β, IL-6, IL-10, and TNFα) and caspase 1 levels were also analyzed. Expression levels of transcription factors (NRF2 and NF-κB) and molecular chaperons (HSF, HSP70, and HSP90) were estimated to evaluate their relative contribution to overcome salinity stress. MDA showed a significant (P < 0.05) increase (gill, + 25.35-90.14%; liver, + 23.88-80.59%) with salinity; SOD (+ 13.72-45.09%) and CAT (+ 12.73-33.96%) exhibited a sharp increase until 9 ppt, followed by a decrease at the highest salinity (12 ppt) (gill, - 3.92%; liver, - 2.18%). Levels of cytokines were observed to increase (+ 52.8-127.42%) in a parallel pattern with increased salinity. HSP70 and HSP90 expressions were higher in gill tissues than those in liver tissues. NRF2 played pivotal role in reducing salinity-induced oxidative load in both the liver and gills. Serum cortisol and carbonic anhydrase were measured and noted to be significantly (P < 0.05) upregulated in salinity stressed groups. Gill Na⁺-K⁺-ATPase activity decreased significantly (P < 0.05) in fish exposed to 6, 9, and 12 ppt compared to control. Present study suggests that a hyperosmotic environment induces acute oxidative stress and inflammation, which in turn causes cellular death and impairs tissue functions in freshwater fish species such as Notopterus chitala.

Effect of low pH and salinity conditions on the antioxidant response and hepatocyte damage in juvenile olive flounder Paralichthys olivaceus

Climate change due to increasing CO₂ emissions results in the increase in water temperatures, which is accompanied by the decrease in pH and salinity levels of the ocean. Ocean acidification reflects the gradual pH reduction due to changes in the carbon chemistry, which is caused by the increase in anthropogenic CO₂ emissions. The subsequent changes in the water temperatures and carbon chemistry of the oceans affect the survival and distribution of aquatic animals. In this study, we analyzed the levels of cortisol, superoxide dismutase, catalase, and caspase-3 in the plasma of juvenile olive flounder Paralichthys olivaceus under combined hyposalinity and acidification. To evaluate the physiological response to these changes, the superoxide dismutase activity and apoptosis were analyzed in the liver cells. Hyposalinity caused oxidative stress and cell damage, while also activating the antioxidant system. Environmental acidification affected the stress response and antioxidant mechanism of P. olivaceus in the early stage of acclimation but did not appear to exceed hyposalinity stress. These findings suggest that a hyposaline environment may be a stronger environmental stressor than an acidifying environment for P. olivaceus, and will help understand the capacity of P. olivaceus to cope with expected future ocean acidification.

In vitro bacterial probiotic selection from Nannostomus beckfordi, an Amazon ornamental fish

ABSTRACT This study aimed to isolate and select in vitro bacteria with probiotic potential for the Amazon ornamental fish Nannostomus beckfordi. For isolate, twelve fish underwent surgery procedure to remove their intestinal tract, macerate and then inoculate in the plate petri containing de Man Rugosa Sharped Agar (MRS). After bacterial growth (48 hours at 35ºC), selected strains were inoculated in MRS broth and submitted to resistance test with NaCl (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0%), pH (4, 5, 6, 8 and 9) and bile salts (5% w/v). Inhibition test against pathogenic bacteria Aeromonas hydrophila, Pseudomonas aeroginosa, Streptococcus agalactiae and Aeromonas Jandaei was also performed. Within the isolated strains group (23 strains), only six (S1, S2, S3, S4, S5 and S6) showed probiotic potential. Strains S1 and S6 showed the greater resistance for NaCl (0.5% and 1%) and pH (5 and 6), but only S1 obtained better results to resist the bile salts. Even against pathogenic bacteria, the S1 showed the best results with inhibition halos greater than 9 mm. In the end, this bacterial strain (S1) was identified as Enterococcus faecium 11037CHB. Thus, this is the first report regarding isolated autochthonous bacterium E. faecium with probiotic potential of N. beckfordi.

Gill Transcriptome Analysis Revealed the Difference in Gene Expression Between Freshwater and Seawater Acclimated Guppy (Poecilia reticulata)

Guppy (Poecilia reticulata) can adapt to a wide range of salinity changes. To investigate the gene expression changes in the guppy exposed to seawater, we characterized its gill transcriptome using RNA sequencing. Experimental fish were exposed to salinity increase from 0 to 30‰ within 4 days, while control fish were cultured in freshwater (0‰ salinity). Seven days after salinity exposure, the gills were sampled and the mortality within 2 weeks was recorded. No significant difference in the cumulative mortality at the second week was found between the two groups. Transcriptomic analysis identified 3477 differentially expressed genes (DEGs), including 1067 upregulated and 2410 downregulated genes. These DEGs were enriched in several biological processes, including ion transport, ion homeostasis, ATP biosynthetic process, metabolic process, and immune system process. Oxidative phosphorylation was the most activated pathway. DEGs involved in the pathway "endoplasmic reticulum (ER)-mediated phagocytosis," "starch and sucrose metabolism," and "steroid biosynthesis" were mainly downregulated; chemokines and interleukins involved in "cytokine-cytokine receptor interaction" were differentially expressed. The present results suggested that oxidative phosphorylation had essential roles in osmoregulation in the gills of seawater acclimated guppy, during which the decline in the expression of genes encoding V-ATPases and calreticulin had a negative effect on the phagocytosis and immune response. Besides, several metabolic processes including "starch and sucrose metabolism" and "steroid biosynthesis" were affected. This study elucidates transcriptomic changes in osmotic regulation, metabolism, and immunity in seawater acclimated guppy.

Enzymatic, non enzymatic antioxidants and glucose metabolism enzymes response differently against metal stress in muscles of three fish species depending on different feeding niche

Current study aims to determine difference in metal accumulation pattern in muscle of Liza parsia (pelagic, omnivore), Amblypharyngodon mola (surface feeder, herbivore) and Mystus gulio (benthic, carnivore) depending on their niche and feeding habit and how it affects the endogenous antioxidants and glucose metabolism in fish muscle. Fishes were collected from Malancha, Diamond Harbour and Chandanpiri, West Bengal, India. Concentrations of lead, zinc, cadmium, chromium were measured in water, sediment and fish muscle. Metal pollution index (MPI) and bioconcentration factor (BCF) was calculated to evaluate the ability of fish to accumulate specific metals in muscle tissue from the aquatic environment. Metal concentrations were found significantly higher (P < 0.05) in water, sediment, fish muscles from Malancha than Chandanpiri and Diamond Harbour. L. parsia (MPI: 0.4-1.6) showed highest metal deposition in their muscle followed by A. mola (MPI: 0.37-1.38) and M. gulio (MPI: 0.2-1.2). Malondealdehyde, superoxide dismutase, catalase, glutathione S transferase, glutathione reductase and cortisol levels increased in case of L. parsia from Malancha and Chandanpiri. Succinate dehydrogenase, lactate dehydrogenase, Ca⁺² ATPase and cytochrome C oxidase levels were significantly (P < 0.05) lower at Malancha and Chandanpiri than Diamond Harbour. Heat shock protein (HSP70) expression was significantly (P < 0.05) higher in all fish species at Malancha followed by Chandanpiri and Diamond Harbour. Glucose, glycogen, hexokinase, phosphofructokinase and glycogen phosphorylase levels varied between sites and selected fish species. Serum cortisol level was measured and found to be the highest in L. parsia from Malancha (2.94 ± 0.12 ng/ml) and the lowest in M. gulio from Diamond Harbour (0.7 ± 0.05 ng/ml). The results indicate that metal toxicity alters antioxidant levels, oxidative status and energy production in fish in species specific manner. Our results also indicate that Mystus has the highest degree of adaptability in response to metal toxicity possibly due to its specific food habit and niche position. Therefore, it can be concluded that maintenance of oxidative and metabolic status to combat metal-induced oxidative load will be helpful for the fishes to acquire better resistance under such eco-physiological stress. Alteration of niche and interactive segregation in aquatic organism may be one of the key modulator of resistance against such stress.

Climate change impacts on fish reproduction are mediated at multiple levels of the brain-pituitary-gonad axis

Anthropogenic emissions of carbon dioxide in the atmosphere have generated rapid variations in atmospheric composition which drives major climate changes. Climate change related effects include changes in physico-chemical proprieties of sea and freshwater, such as variations in water temperature, salinity, pH/pCO₂ and oxygen content, which can impact fish critical physiological functions including reproduction. In this context, the main aim of the present review is to discuss how climate change related effects (variation in water temperature and salinity, increases in duration and frequency of hypoxia events, water acidification) would impact reproduction by affecting the neuroendocrine axis (brain-pituitary-gonad axis). Variations in temperature and photoperiod regimes are known to strongly affect sex differentiation and the timing and phenology of spawning period in several fish species. Temperature mainly acts at the level of gonad by interfering with steroidogenesis, (notably on gonadal aromatase activity) and gametogenesis. Temperature is also directly involved in the quality of released gametes and embryos development. Changes in salinity or water acidification are especially associated with reduction of sperm quality and reproductive output. Hypoxia events are able to interact with gonad steroidogenesis by acting on the steroids precursor cholesterol availability or directly on aromatase action, with an impact on the quality of gametes and reproductive success. Climate change related effects on water parameters likely influence also the reproductive behavior of fish. Although the precise mechanisms underlying the regulation of these effects are not always understood, in this review we discuss different hypothesis and propose future research perspectives.

Effect of salt stress on in vitro organogenesis from nodal explant of Limnophila aromatica (Lamk.) Merr. and Bacopa monnieri (L.) Wettst. and their physio-morphological and biochemical responses

Salinity is one of the most severe abiotic stress factors that limit crop productivity by affecting the growth of plants. Therefore, it is significant to know the responses of plants against salt stress. In this study, the callus formation capabilities of nodal explants of Limnophila aromatica (Lamk.) Merr. and Bacopa monnieri (L.) Wettst. incubated under different NaCl concentrations (0-100 mM) in in vitro culture conditions were investigated and also the effect of NaCl on the release of regenerated shoots from these calluses was examined. Furthermore, the plants under NaCI stress were evaluated physiologically and biochemically. Callus formation percentages and callus intensities from the nodal explants decreased with increasing NaCl concentrations. In addition, yellowing, browning and even deaths were observed in calluses under salt toxicity. The callus was taken into the subculture, and the increased NaCl concentration in both plant species adversely affected the regeneration ability of the shoots. The number of shoots per callus for L. aromatica and B. monnieri was 6.72-17.49 and 7.42-15.38, respectively. The length of shoots in L. aromatica was between 0.95 and 1.65 cm, and in B. monnieri between 1.17 and 1.81 cm. The lowest number of shoots per callus and the shoot lengths were found in medium containing 100 mM NaCl. Moreover, photosynthetic pigmentation, lipid peroxidation, protein content, and proline content was damaged with increased salinity compared to the control group. This comprehensive study in tissue culture conditions can a be potential contributor to the literature and can help other studies to be carried out in the future.

Prophylactic treatment with MSC-derived exosomes attenuates traumatic acute lung injury in rats

The mesenchymal stem cell (MSC) is a potential strategy in the pretreatment of traumatic acute lung injury (ALI), a disease that causes inflammation and oxidative stress. This study aimed to investigate whether MSC-exosomal microRNA-124-3p (miR-124-3p) affects traumatic ALI. Initially, a traumatic ALI rat model was established using the weight-drop method. Then, exosomes were obtained from MSCs of Sprague-Dawley rats, which were injected into the traumatic ALI rats. We found that miR-124-3p was abundantly-expressed in MSCs-derived exosomes and could directly target purinergic receptor P2X ligand-gated ion channel 7 (P2X7), which was overexpressed in traumatic ALI rats. After that, a loss- and gain-of-function study was performed in MSCs and traumatic ALI rats to investigate the role of miR-124-3p and P2X7 in traumatic ALI. MSC-derived exosomal miR-124-3p or silenced P2X7 was observed to increase the survival rate of traumatic ALI rats and enhance the glutathione/superoxide dismutase activity in their lung tissues. However, the wet/dry weight of lung tissues, activity of methylenedioxyamphetamine and H2O2, and levels of inflammatory factors (TNF-a, IL-6, and IL-8) were reduced. Similarly, the numbers of total cells, macrophages, neutrophils, and lymphocytes in bronchoalveolar lavage fluid were also reduced when treated with exosomal miR-124-3p or silenced P2X7. In conclusion, the results provide evidence that miR-124-3p transferred by MSC-derived exosomes inhibited P2X7 expression, thus improving oxidative stress injury and suppressing inflammatory response in traumatic ALI, highlighting a potential pretreatment for traumatic ALI.