Transition of autophagy and apoptosis in fibroblasts depends on dominant expression of HIF-1αor p53

It has been revealed that hypoxia is dynamic in hypertrophic scars;therefore,we considered that it may have different effects on hypoxia-inducible factor-1α(HIF-1α)and p53 expression.Herein,we aimed to confirm the presence of a teeterboard-like conversion between HIF-1αand p53,which is correlated with scar formation and regression.Thus,we obtained samples of normal skin and hypertrophic scars to identify the differences in HIF-1αand autophagy using immunohistochemistry and transmission electron microscopy.In addition,we used moderate hypoxia in vitro to simulate the proliferative scar,and silenced HIF-1αor p53 gene expression or triggered overexpression to investigate the changes of HIF-1αand p53 expression,autophagy,apoptosis,and cell proliferation under this condition.HIF-1α,p53,and autophagy-related proteins were assayed using western blotting and immunofluorescence,whereas apoptosis was detected using flow cytometry analysis,and cell proliferation was detected using cell counting kit-8(CCK-8)and 5-bromo-2′-deoxyuridine(BrdU)staining.Furthermore,immunoprecipitation was performed to verify the binding of HIF-1αand p53 to transcription cofactor p300.Our results demonstrated that,in scar tissue,HIF-1αexpression increased in parallel with autophagosome formation.Under hypoxia,HIF-1αexpression and autophagy were upregulated,whereas p53 expression and apoptosis were downregulated in vitro.HIF-1αknockdown downregulated autophagy,proliferation,and p300-bound HIF-1α,and upregulated p53 expression,apoptosis,and p300-bound p53.Meanwhile,p53 knockdown induced the opposite effects and enhanced HIF-1α,whereas p53 overexpression resulted in the same effects and reduced HIF-1α.Our results suggest a teeterboard-like conversion between HIF-1αand p53,which is linked with scar hyperplasia and regression.

The Novel PRRSV Strain HBap4-2018 with a Unique Recombinant Pattern Is Highly Pathogenic to Piglets

Currently, various porcine reproductive and respiratory syndrome virus(PRRSV) variants emerged worldwide with different genetic characteristics and pathogenicity, increasing the difficulty of PRRS control. In this study, a PRRSV strain named HBap4-2018 was isolated from swine herds suffering severe respiratory disease with high morbidity in Hebei Province of China in 2018. The genome of HBap4-2018 is 15,003 nucleotides in length, and compared with NADC30-like PRRSV, nsp2 of HBap4-2018 has an additional continuous deletion of five amino acids. Phylogenetic analysis based on complete genome and ORF5 showed that HBap4-2018 belonged to lineage 8 of PRRSV-2, which was characterized by highly variable genome. However, HBap4-2018 was classified into lineage 1 based on phylogenetic analysis of nsp2,sharing higher amino acid homology(85.3%–85.5%) with NADC30-like PRRSV. Further analysis suggested that HBap4-2018 was a novel natural recombinant PRRSV with three recombinant fragments in the genome, of which highly pathogenic PRRSV(HP-PRRSV) served as the major parental strains, while NADC30-like PRRSV served as the minor parental strains. Five recombination break points were identified in nsp2, nsp3, nsp5, nsp9 and ORF6, respectively,presenting a novel recombinant pattern in the genome. Piglets inoculated with HBap4-2018 presented typical clinical signs with a mortality rate of 60%. High levels of viremia and obvious macroscopic and histopathological lesions in the lungs were observed, revealing the high pathogenicity of HBap4-2018 in piglets.