Hypoxia serves a key function in the upregulated expression of vascular adhesion protein‑1 in vitro and in a rat model of hemorrhagic shock

Endothelial cell-derived SSAO can increase MLC20 phosphorylation in VSMCs

Vascular hyporesponsiveness in the shock decompensation period is an important factor leading to death. Myosin light chain 20 (MLC₂₀) is the main effector protein that regulates vascular reactivity. However, whether the change in semicarbazide-sensitive amine oxidase (SSAO) expression during hypoxia can change the MLC₂₀ phosphorylation level, and its underlying mechanism were not clear. The amine oxidase copper containing 3 (AOC3) overexpressing adenovirus vector was constructed and transfected into rat intestinal microvascular endothelial cells (RIMECs) to overexpress SSAO, and the RIMECs were co-cultured with rat intestinal microvascular smooth muscle cells (RIMSCs). The changes in SSAO/inducible nitric oxide synthase (iNOS)/Rho associate coiled-coil containing protein kinase 1 (ROCK1) expression levels and MLC₂₀ phosphorylation level were detected. Here we found that the increased SSAO by AOC3 overexpression can decrease the iNOS expression level and its activity after hypoxia. In addition, RIMSCs co-cultured with RIMECs overexpressed with AOC3 gene had significantly higher ROCK1 protein level and MLC₂₀ phosphorylation level than RIMSCs co-cultured with normal RIMECs. Our study demonstrated that SSAO overexpression can significantly inhibit iNOS activity, promote RhoA/ROCK pathway activation, and increase the phosphorylation level of MLC₂₀, which might be the potential mechanism in relieving the vascular hyporesponsiveness during shock decompensation.

What lies beneath? Molecular evolution during the radiation of caecilian amphibians

Background

Evolution leaves an imprint in species through genetic change. At the molecular level, evolutionary changes can be explored by studying ratios of nucleotide substitutions. The interplay among molecular evolution, derived phenotypes, and ecological ranges can provide insights into adaptive radiations. Caecilians (order Gymnophiona), probably the least known of the major lineages of vertebrates, are limbless tropical amphibians, with adults of most species burrowing in soils (fossoriality). This enigmatic order of amphibians are very distinct phenotypically from other extant amphibians and likely from the ancestor of Lissamphibia, but little to nothing is known about the molecular changes underpinning their radiation. We hypothesised that colonization of various depths of tropical soils and of freshwater habitats presented new ecological opportunities to caecilians.

Results

A total of 8540 candidate groups of orthologous genes from transcriptomic data of five species of caecilian amphibians and the genome of the frog Xenopus tropicalis were analysed in order to investigate the genetic machinery behind caecilian diversification. We found a total of 168 protein-coding genes with signatures of positive selection at different evolutionary times during the radiation of caecilians. The majority of these genes were related to functional elements of the cell membrane and extracellular matrix with expression in several different tissues. The first colonization of the tropical soils was connected to the largest number of protein-coding genes under positive selection in our analysis. From the results of our study, we highlighted molecular changes in genes involved in perception, reduction-oxidation processes, and aging that likely were involved in the adaptation to different soil strata.

Conclusions

The genes inferred to have been under positive selection provide valuable insights into caecilian evolution, potentially underpin adaptations of caecilians to their extreme environments, and contribute to a better understanding of fossorial adaptations and molecular evolution in vertebrates.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5694-1) contains supplementary material, which is available to authorized users.