Tilapia lake virus causes mitochondrial damage: a proposed mechanism that leads to extensive death in fish cells.

Background: Tilapia lake virus (TiLV), also known as Tilapinevirus tilapiae, poses a significant threat to tilapia aquaculture, causing extensive mortality and economic losses. Understanding the mechanisms and pathogenesis of TiLV is crucial to mitigate its impact on this valuable fish species. Methodology: In this study, we utilized transmission electron microscopy to investigate the ultrastructural changes in E-11 cells following TiLV infection. We also examined the presence of TiLV particles within the cells. Cellular viability and mitochondrial functions were assessed using MTT and ATP measurement assays and mitochondrial probes including JC-1 staining and MitoTracker™ Red. Results: Our findings provide novel evidence demonstrating that TiLV causes cytotoxicity through the destruction of mitochondria. Transmission electron micrographs showed that TiLV particles were present in the cytoplasm of E-11 cells as early as 1 h after infection. Progressive swelling of mitochondria and ultrastructural damage to the cells were observed at 1, 3 and 6 days post-infection. Furthermore, losses of mitochondrial mass and membrane potential (MMP) were detected at 1 day after TiLV inoculation, as determined by mitochondrial probes. The results of the MTT assay also supported the hypothesis that the cell deaths in E-11 cells during TiLV infection may be caused by the disruption of mitochondrial structure and function. Conclusions: Our study reveals the significant role of mitochondrial disruption in contributing to cellular death during the early stages of TiLV infection. These findings advance the understanding of TiLV pathogenesis and further enhance our knowledge of viral diseases in fish.

Activation of liver X receptors reduces CFTR-mediated Cl(-) transport in kidney collecting duct cells.

Liver X receptors (LXRs) are transcription factors belonging to the nuclear receptor super family, which act as regulators of lipid and glucose metabolism. However, LXRs have been shown to regulate the function of transporters in the kidney, including the Na-Pi cotransporter, organic anion transporter, and epithelial Na(+) channel. In this report, we demonstrated the ability of LXR ligands, both endogenous [22 (R)-hydroxycholesterol] and synthetic (T0901317 and GW3965), to reduce CFTR-mediated Cl(-) secretion in a type I Madin-Darby canine kidney (MDCK) cell line and in murine primary inner medullary collecting duct (IMCD) cells, based on measurements of [Arg(8)]-vasopressin-induced Cl(-) current. However, treatment of MDCK cell monolayers with 5 µM T0901317 for 24 h did not alter ouabain-senstive current or Na(+)-K(+)-ATPase-α protein content. Furthermore, basolateral membranes permeabilization of MDCK cell monolayers still resulted in a decrease in apical Cl(-) current stimulated by both [Arg(8)]-vasopressin and 8-cholorophenyl-thio-cAMP, indicating that the factor(s) encoded by the target gene(s) of agonist-activated LXRs might be located at the apical membrane. Western blot analysis revealed that inhibition of Cl(-) secretion occurred via a decrease in CFTR protein, which was not due to downregulation of its mRNA expression. In addition, both synthetic LXR agonists significantly retarded the growth of forskolin-induced cysts formed in MDCK cells cultured in collagen gel. This is the first evidence showing that ligand-activated LXRs are capable of downregulating CFTR-mediated Cl(-) secretion of kidney cells and of retarding cyst growth in a MDCK cell model.