Protective effect of protexin concentrate in reducing the toxicity of chlorpyrifos in common carp (Cyprinus carpio)

The present study aimed to evaluate the protective effect of protexin supplementation against chlorpyrifos-induced oxidative stress and immunotoxicity in Cyprinus carpio. After 21 days, the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR), and total antioxidant levels significantly decreased in hepatocytes of fish exposed to chlorpyrifos, while malondialdehyde (MDA) increased. Treatment with protexin was able to reverse the decrease in SOD and GR and significantly reduce MDA levels. Exposure to chlorpyrifos also induced alterations in blood biochemical parameters and caused immunosuppression. Dietary protexin return some parameters (aspartate aminotransferase, lactate dehydrogenase, and γ-glutamyltransferase activities, and glucose, cholesterol, total protein, creatinine, and complement C4 levels) to values similar to those of the control group. Based on the results, it can be concluded that protexin exerted protective effects against chlorpyrifos exposure in C. carpio reducing oxidative damage, and ameriorating blood biochemical alterations and the immunosuppression.

The Protexin complex counters resection on stalled forks to promote homologous recombination and crosslink repair

Protection of stalled replication forks is critical to genomic stability. Using genetic and proteomic analyses, we discovered the Protexin complex containing the ssDNA binding protein SCAI and the DNA polymerase REV3. Protexin is required specifically for protecting forks stalled by nucleotide depletion, fork barriers, fragile sites, and DNA inter-strand crosslinks (ICLs), where it promotes homologous recombination and repair. Protexin loss leads to ssDNA accumulation and profound genomic instability in response to ICLs. Protexin interacts with RNA POL2, and both oppose EXO1's resection of DNA on forks remodeled by the FANCM translocase activity. This pathway acts independently of BRCA/RAD51-mediated fork stabilization, and cells with BRCA2 mutations were dependent on SCAI for survival. These data suggest that Protexin and its associated factors establish a new fork protection pathway that counteracts fork resection in part through a REV3 polymerase-dependent resynthesis mechanism of excised DNA, particularly at ICL stalled forks.