Expression profiling and antibacterial analysis of cd36 in mandarin fish, Siniperca chuatsi.

Cd36 is classified as a class B scavenger receptor and has also been identified as a pattern recognition receptor. In this study, we investigated the genomic structure and molecular characteristics of cd36 in mandarin fish (Siniperca chuatsi), examined its tissue distribution, and evaluated its antibacterial activity. Genomic structure analysis showed that Sccd36 consists of 12 exons and 11 introns. Sequencing analysis confirmed that the open reading frame of Sccd36 contains 1410 bp, encoding 469 amino acids. Sccd36 is deeply conserved with other vertebrates in terms of genomic structure, gene loci and molecular evolution, and the feature of two transmembrane was observed in ScCd36 through structural prediction. Sccd36 was constitutively expressed in all tissues tested, with the strongest expression in the intestine, followed by the heart and the kidney. Dramatic changes of Sccd36 mRNA were detected in mucosal tissues, including the intestine, gill and skin, when stimulated by the microbial ligands lipopolysaccharide and lipoteichoic acid. In addition, ScCd36 was identified as having strong binding ability to microbial ligands and antibacterial activity against the gram-negative bacteria Aeromonas hydrophila and the gram-positive bacteria Streptococcus lactis. Furthermore, we verified that the genetic ablation of cd36 impaired the resistance of fish to bacterial challenge by using zebrafish cd36 knockout line. In conclusion, our findings suggest that ScCd36 plays a crucial role in the innate immune response of mandarin fish against bacterial infections. This also sets the stage for further exploration into the antibacterial function of Cd36 in lower vertebrate species.

Effects of negative pressure wound therapy on surgical site wound infections after cardiac surgery: A meta-analysis.

We conducted a comprehensive analysis to evaluate the benefits of negative pressure wound therapy (NPWT) versus traditional dressings in preventing surgical site infections in patients undergoing cardiac surgery. We thoroughly examined several databases, including PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure (CNKI), VIP, Chinese Biomedical Literature Database (CBM) and Wanfang, from inception until July 2023. Two independent researchers were responsible for the literature screening, data extraction and quality assessment; analyses were performed using RevMan 5.4 software. Thirteen studies comprising 8495 patients were deemed relevant. A total of 2685 patients were treated with NPWT, whereas 5810 received conventional dressings. The findings revealed that NPWT was more effective in reducing surgical site infections after cardiac surgery than conventional dressings (4.88% vs. 5.87%, odds ratio [OR]: 0.50, 95% confidence intervals [CIs]: 0.40-0.63, p < 0.001). Additionally, NPWT was more effective in reducing deep wound infections (1.48% vs. 4.15%, OR: 0.36, 95% CI: 0.23-0.56, p < 0.001) and resulted in shorter hospital stays (SMD: -0.33, 95% CIs: -0.54 to -0.13, p = 0.001). However, the rate of superficial wound infections was not significantly affected by the method of wound care (3.72% vs. 5.51%, OR: 0.63, 95% CI: 0.32-1.23, p = 0.180). In conclusion, NPWT was shown to be advantageous in preventing postoperative infections and reducing hospital stay durations in patients undergoing cardiac surgery. Nonetheless, given the limitations in the number and quality of the included studies, further research is recommended to validate these findings.

Congenital asplenia due to a tlx1 mutation reduces resistance to Aeromonas hydrophila infection in zebrafish.

It is documented that tlx1, an orphan homeobox gene, plays critical roles in the regulation of early spleen developmental in mammalian species. However, there is no direct evidence supporting the functions of tlx1 in non-mammalian species, especially in fish. In this study, we demonstrated that tlx1 is expressed in the splenic primordia as early as 52 hours post-fertilization (hpf) in zebrafish. A tlx1-/- homozygous mutant line was generated via CRISPR/Cas9 to elucidate the roles of tlx1 in spleen development in zebrafish. In the tlx1-/- background, tlx1-/- cells persisted in the splenic primordia until 52 hpf but were no longer detectable after 53 hpf, suggesting perturbation of early spleen development. The zebrafish also exhibited congenital asplenia caused by the tlx1 mutation. Asplenic zebrafish can survive and breed normally under standard laboratory conditions, but the survival rate of animals infected with Aeromonas hydrophila was significantly lower than that of wild-type (WT) zebrafish. In asplenic zebrafish, the mononuclear phagocyte system was partially impaired, as demonstrated by retarded b7r expression and reduced ccr2 expression after injection with an inactivated A. hydrophila vaccine. Furthermore, the expression of MHCII/IgM was significantly reduced in the congenitally asplenic fish compared with that of the WT zebrafish. Taken together, our data suggest that tlx1 is a crucial regulator of spleen development in fish, as it is in mammals. We have also provided a new perspective for studying the role of the spleen during pathogen challenge in fish.

Congenital asplenia impairs heme-iron recycling during erythropoiesis in zebrafish.

The spleen is postulated to be a hematopoietic tissue in adult fish; however, clear evidence is still lacking to define its role in hematopoietic activity. In our previous study, a congenitally asplenic zebrafish was generated though gene editing, which provided a new perspective for studying the role of fish spleen in hematopoiesis. In this study, HSC-regulated and erythrocyte marker genes, such as gata1a, gata2, klf1, hbaa1, hbaa2, hbba1 and hbba2 were significantly reduced in congenitally asplenic zebrafish when compared with wild-type (WT). Subsequently, we conducted the transcriptome profiles of whole kidneys from WT and congenitally asplenic zebrafish to explore the possible molecular mechanisms underlying the impaired erythropoiesis caused by congenital asplenia. Our results demonstrated that congenital asplenia might impair heme-iron recycling during erythropoiesis, as evidenced by significant down-regulation of genes associated with iron acquisition (tfr1a, tfa, steap3 and slc25a37) and heme biosynthesis and transport (alas2, fech, uros, urod, copx, ppox and abcb10) in congenitally asplenic zebrafish. In addition, the down-regulation of hemopoiesis-related GO terms, including heme binding, tetrapyrrole binding, iron ion binding, heme metabolic process, heme biosynthetic process, erythrocyte differentiation, iron ion homeostasis and hemoglobin metabolic process confirmed the impaired erythropoiesis induced by congenital asplenia. Our study provides an in-depth understanding of spleen function in regulating heme-iron homeostasis during hematopoiesis, thereby providing valuable insights into pathological responses in splenectomized or congenitally asplenic patients.

Perfluorooctanoic acid triggers premature ovarian insufficiency by impairing NAD+ synthesis and mitochondrial function in adult zebrafish.

High-dose perfluorooctanoic acid (PFOA) impairs oocyte maturation and offspring quality. However, the physiological concentrations of PFOA in follicular fluids of patients with premature ovarian insufficiency (POI) were detected at lower levels, thus the relationship between physiological PFOA and reproductive disorders remains elusive. Here, we investigated whether physiological PFOA exposure affects gonad function in adult zebrafish. Physiological PFOA exposure resulted in POI-like phenotypes in adult females, which exhibited decreased spawning frequency, reduced number of ovulated eggs, abnormal gonadal index, and aberrant embryonic mortality. Meanwhile, oocytes from PFOA-exposed zebrafish showed mitochondrial disintegration and diminished mitochondrial membrane potential. Unlike the high-dose treated oocytes exhibiting high reactive oxygen species (ROS) levels and excessive apoptosis, physiological PFOA reduced the ROS levels and did not trigger apoptosis. Interestingly, physiological PFOA exposure would not affect testis function, indicating specific toxicity in females. Mechanistically, PFOA suppressed the NAD+ biosynthesis and impaired mitochondrial function in oocytes, thus disrupting oocyte maturation and ovarian fertility. Nicotinamide mononucleotide (NMN), a precursor for NAD+ biosynthesis, alleviated the PFOA-induced toxic effects in oocytes and improved the oocyte maturation and fertility upon PFOA exposure. Our findings discover new insights into PFOA-induced reproductive toxicity and provide NMN as a potential drug for POI therapy.

Eugenol exposure inhibits embryonic development and swim bladder formation in zebrafish.

Eugenol is a natural phenolic essential oil extracted from cloves, that has analgesic and anesthetic effects and is widely used in fishery anesthesia. However, the potential safety risks of aquaculture production associated with the massive use of eugenol and its developmental toxicity during early life stages of fish have been overlooked. In this study, zebrafish (Danio rerio) embryos at 24 hours post-fertilization (hpf) were exposed to eugenol at concentrations of 0, 10, 15, 20, 25, or 30 mg/L for 96 h. Eugenol exposure delayed the hatching of zebrafish embryos, and reduced the body length and the inflation rate of the swim bladder. The accumulated number of dead zebrafish larvae in the eugenol-exposed groups was higher than that of the control group, and it was dose-dependent. Real-time quantitative polymerase chain reaction (qPCR) analysis showed that the Wnt/ß-catenin signaling pathway that regulates the development of the swim bladder during the hatching and mouth-opening stages was inhibited after eugenol exposure. Specifically, the expression of wif1, a Wnt signaling pathway inhibitor, was significantly up-regulated, whereas the expression of fzd3b, fzd6, ctnnb1, and lef1 involved in the Wnt/ß-catenin pathway was significantly down-regulated. These results suggest that the failure of zebrafish larvae to inflate their swim bladders as a result of eugenol exposure may be caused by the inhibition of the Wnt/ß-catenin signaling pathway inhibited. In addition, the inability to catch food due to the abnormal development of the swim bladder may be the key to the death of zebrafish larvae during the mouth-opening stage.

Congenital Asplenia Interrupts Immune Homeostasis and Leads to Excessive Systemic Inflammation in Zebrafish.

Splenectomy or congenital asplenia in humans increases susceptibility to infections. We have previously reported that congenital asplenia in zebrafish reduces resistance to Aeromonas hydrophila infection. However, the molecular mechanism of systemic immune response in congenitally asplenic individuals is largely unexplored. In this study, we found that pro-inflammatory cytokines were more highly induced in congenitally asplenic zebrafish than wild-type after pathogenic A. hydrophila infection and lipopolysaccharide exposure. In addition, a higher aggregation of apoptotic cells was observed in congenitally asplenic zebrafish than that in wild-type. Next, we examined the transcriptome profiles of whole kidneys from wild-type and congenitally asplenic zebrafish to investigate the effects of congenital asplenia on innate and adaptive immune responses induced by the inactivated A. hydrophila. Congenital asplenia inactivated the splenic anti-inflammatory reflex, disrupted immune homeostasis, and induced excessive inflammation as evidenced by the highly induced stress response-related biological processes, inflammatory and apoptosis-associated pathways, and pro-inflammatory cytokines/chemokines in congenitally asplenic zebrafish compared with wild-type after vaccination. In addition, complement component genes (c3a.1, c3a.6, c4, c6, and c9) and several important immune-related genes (tabp.1, tap1, hamp, prg4b, nfil3, defbl1, psmb9a, tfr1a, and sae1) were downregulated in congenitally asplenic zebrafish. Furthermore, congenital asplenia impaired adaptive immunity as demonstrated by downregulation of biological processes and signaling pathways involved in adaptive immune response after vaccination in congenitally asplenic zebrafish. The expression of MHCII/IgM was also significantly reduced in the congenitally asplenic zebrafish when compared with wild-type. Together, our study provides an in-depth understanding of spleen function in controlling immune homeostasis and may offer insight into the pathological response in splenectomized or congenitally asplenic patients after infections.

A Model Construction of Starvation Induces Hepatic Steatosis and Transcriptome Analysis in Zebrafish Larvae.

Hepatic steatosis caused by starvation, resulting in non-alcoholic fatty liver disease (NAFLD), has been a research topic of human clinical and animal experiments. To understand the molecular mechanisms underlying the triggering of abnormal liver metabolism by starvation, thus inducing hepatic lipid accumulation, we used zebrafish larvae to establish a starvation-induced hepatic steatosis model and conducted comparative transcriptome analysis by RNA-seq. We demonstrated that the incidence of larvae steatosis is positively correlated with starvation time. Under starvation conditions, the fatty acid transporter (slc27a2a and slc27a6-like) and fatty acid translocase (cd36) were up-regulated significantly to promote extrahepatic fatty acid uptake. Meanwhile, starvation inhibits the hepatic fatty acid metabolism pathway but activates the de novo lipogenesis pathway to a certain extent. More importantly, we detected that the expression of numerous apolipoprotein genes was downregulated and the secretion of very low density lipoprotein (VLDL) was inhibited significantly. These data suggest that starvation induces hepatic steatosis by promoting extrahepatic fatty acid uptake and lipogenesis, and inhibits hepatic fatty acid metabolism and lipid transport. Furthermore, we found that starvation-induced hepatic steatosis in zebrafish larvae can be rescued by targeting the knockout cd36 gene. In summary, these findings will help us understand the pathogenesis of starvation-induced NAFLD and provide important theoretical evidence that cd36 could serve as a potential target for the treatment of NAFLD.

Zebrafish Oxr1a Knockout Reveals Its Role in Regulating Antioxidant Defenses and Aging.

Oxidation resistance gene 1 (OXR1) is essential for protection against oxidative stress in mammals, but its functions in non-mammalian vertebrates, especially in fish, remain uncertain. Here, we created a homozygous oxr1a-knockout zebrafish via the CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR associated protein 9) system. Compared with wild-type (WT) zebrafish, oxr1a-/- mutants exhibited higher mortality and more apoptotic cells under oxidative stress, and multiple antioxidant genes (i.e., gpx1b, gpx4a, gpx7 and sod3a) involved in detoxifying cellular reactive oxygen species were downregulated significantly. Based on these observations, we conducted a comparative transcriptome analysis of early oxidative stress response. The results show that oxr1a mutation caused more extensive changes in transcriptional networks compared to WT zebrafish, and several stress response and pro-inflammatory pathways in oxr1a-/- mutant zebrafish were strongly induced. More importantly, we only observed the activation of the p53 signaling and apoptosis pathway in oxr1a-/- mutant zebrafish, revealing an important role of oxr1a in regulating apoptosis via the p53 signaling pathway. Additionally, we found that oxr1a mutation displayed a shortened lifespan and premature ovarian failure in prolonged observation, which may be caused by the loss of oxr1a impaired antioxidant defenses, thereby increasing pro-apoptotic events. Altogether, our findings demonstrate that oxr1a is vital for antioxidant defenses and anti-aging in zebrafish.