This study investigated how Atlantic sturgeon cells respond to elevated temperatures, shedding light on the potential impacts of climate change on fish. Atlantic sturgeon (Acipenser oxyrinchus), an IUCN (International Union for Conservation of Nature) Red List species and evolutionarily related to paleonisiform species, may have considerable physiological adaptability, suggesting that this species may be able to cope with changing climatic conditions and higher temperatures. To test this hypothesis, the AOXlar7y cell line was examined at 20 °C (control) and at elevated temperatures of 25 °C and 28 °C. Parameters including proliferation, vitality, morphology, and gene expressions related to proliferation, stemness, and stress were evaluated. Additionally, to achieve a comprehensive understanding of cellular changes, mitochondrial and metabolic activities were assessed using Seahorse XF96. AOXlar7y cells adapted to 28 °C exhibited enhanced mitochondrial adaptability, plasticity, heightened cell proliferation, and increased hsp70 expression. Increased baseline respiration indicated elevated ATP demand, which is potentially linked to higher cell proliferation and heat stress defense. Cells at 28 °C also displayed elevated reserve respiration capacity, suggesting adaptation to energy demands. At 25 °C, AOXlar7y cells showed no changes in basal respiration or mitochondrial capacity, suggesting unchanged ATP demand compared to cells cultivated at 20 °C. Proliferation and glycolytic response to energy requirements were diminished, implying a connection between glycolysis inhibition and proliferation suppression. These research results indicate sturgeon cells are capable of withstanding and adapting to an 8 °C temperature increase. This cellular analysis lays a foundation for future studies aimed at a deeper understanding of fish cell physiological adaptations, which will contribute to a better knowledge of environmental threats facing Atlantic sturgeon and fish populations amid climate change.

A stimulated renin-angiotensin system is known to promote oxidative stress, apoptosis, necrosis and fibrosis. Renin transcripts (renin-b; renin-c) encoding a cytosolic renin isoform have been discovered that may in contrast to the commonly known secretory renin (renin-a) exert protective effects Here, we analyzed the effect of renin-a and renin-b overexpression in H9c2 cardiomyoblasts on apoptosis and necrosis as well as on potential mechanisms involved in cell death processes. To mimic ischemic conditions, cells were exposed to glucose starvation, anoxia or combined oxygen–glucose deprivation (OGD) for 24 h. Under OGD, control cells exhibited markedly increased necrotic and apoptotic cell death accompanied by enhanced ROS accumulation, loss of mitochondrial membrane potential and decreased ATP levels. The effects of OGD on necrosis were exaggerated in renin-a cells, but markedly diminished in renin-b cells. However, with respect to apoptosis, the effects of OGD were almost completely abolished in renin-b cells but interestingly also moderately diminished in renin-a cells. Under glucose depletion we found opposing responses between renin-a and renin-b cells; while the rate of necrosis and apoptosis was aggravated in renin-a cells, it was attenuated in renin-b cells. Based on our results, strategies targeting the regulation of cytosolic renin-b as well as the identification of pathways involved in the protective effects of renin-b may be helpful to improve the treatment of ischemia-relevant diseases.

The classical secretory renin-a is known to be involved in angiotensin generation, thereby regulating not only blood pressure, but also promoting oxidative stress as well as apoptotic and necrotic cell death. In contrast, another cytosolic renin isoform named renin-b has been described, exerting protective effects under ischemia-related conditions in H9c2 cardiomyoblasts. Using microarray-based transcriptome analyses, we aimed to identify the signaling pathways involved in mediating cardioprotection in H9c2 cells overexpressing renin-b. By transcriptome profiling, we identified increased gene expression of several genes encoding glycolytic enzymes and glucose transporters, while the transcript levels of TCA-cycle enzymes were decreased. Complementing data from metabolic analyses revealed enhanced glucose consumption and lactate accumulation due to renin-b overexpression. Renin-b overexpression further stimulated AKT/mTOR signaling, where numerous genes involved in this pathway showed altered transcript levels. For AKT, we also detected enhanced phosphorylation levels by means of Western blotting, suggesting an activation of this kinase. Moreover, analysis of the ROS levels identified an increase in ROS accumulation in renin-b-overexpressing cells. Altogether, our data demonstrate that renin-b overexpression induces the metabolic remodeling of H9c2 cells similar to that seen under oxygen deprivation. This metabolic phenotype exerting so-called aerobic glycolysis is also known as the Warburg effect.

Sturgeons, once resilient enough to outlive dinosaurs, are now critically endangered. All 26 species of Acipenseriformes face extinction due to anthropogenic causes. Despite their ecological and economic significance, sturgeon research lacks essential tools such as larval cell lines; the Cellosaurus database lists only one larval cell line (AOXlar7y from Atlantic sturgeon). Larval stages are key to understand fish development, representing a transitional phase between embryonic and adult life that is highly sensitive to temperature shifts, oxygen depletion and pollution. Larval cell lines therefore provide potential in vitro models for studying development and stress responses in endangered species. This study focused on establishing and initially characterizing five novel larval cell lines from siblings of the Siberian sturgeon (Acipenser baerii). The lines proved viable for long-term culture, bio-banking and transfer, displaying different morphologies ranging from epithelial-like to fibroblast-like. Functional assays showed variable mitochondrial activity and extracellular acidification rates. A preliminary targeted gene expression analysis revealed similarity to whole larvae within early passages and in vitro adaptations for certain genes (gapdh, vim, col1a1, pcna). These sibling-derived cell lines hold potential as in vitro tools to deeper explore the biology of Siberian sturgeon larvae and support conservation-focused research.

Physiological changes in animals induced by environmental shifts in aquatic ecosystems can be studied using fish cell lines derived from vulnerable species. Therefore, we investigated how environmental shifts—specifically, an increase of 5 °C in temperature—impact the physiology of the cell line CMAfin1 derived from maraena whitefish (Coregonus maraena). Cellular growth, morphology, and metabolic responses were examined under two growth conditions: a control temperature of 20 °C and an elevated temperature of 25 °C. Using trypan blue staining, automated cell counting, phase contrast microscopy, and actin staining, we observed morphological changes in the cells. Metabolic functions were assessed using a Seahorse XFe96 Flux Analyzer, focusing on the bioenergetic capacities of mitochondrial respiration and glycolytic activity. Hyperthermia resulted in faster growth rates but reduced cell size in the CMAfin1 cell line. The cells’ metabolic activity (mitochondrial respiration and glycolytic activity) was inhibited, leading to a quiescent energy state. Our findings indicate reduced motility and altered intercellular communication at higher temperatures. The results highlight the potential of in vitro models to study environmental stress on fish physiology and emphasize the value of fish cell lines for understanding metabolic responses.

Two different renin isoforms are expressed in extrarenal tissues. The classical renin-a has been associated with detrimental effects, whereas renin-b exerts protective effects during glucose starvation. Glucose starvation selectively increased renin-b mRNA levels. 8Br-cAMP increased renin-a mRNA levels independently of glucose as well as of renin-b in glucose-starved cells. Adenylyl cyclase (AC) stimulation by forskolin increased expression of both renin transcripts, while AC inhibition by SQ22536 produced the opposite effect. PKA inhibition by KT5720 reduced the mRNA levels of both renin transcripts glucose-independently. Forskolin reversed the effect of KT5720 on renin mRNA levels. A23187-mediated increase in [Ca²⁺]i increased renin-b mRNA levels in glucose-starved cells. Ca²⁺ chelator BAPTA decreased renin-a mRNA expression in control cells and renin-b levels glucose-independently. Forskolin reversed the BAPTA-mediated decreases in renin-a but not renin-b expression. While the regulation of renin transcript levels by cAMP and PKA resembled known regulation in the kidney, the effect of intracellular free Ca²⁺ levels were opposite. This supports the existence of a separate renin system in cardiac cells.