Autophagy in hematopoietic stem cell development of the embryo.

Hematopoietic stem cells (HSC) emerge from hemogenic endothelial cells (HEC) in the aorta-gonad-mesonephros (AGM) region of embryos, which go through the pre-HSC process. Various intrinsic and extrinsic factors are involved in this process. We recently discovered that the existence of distinct macroautophagic/autophagic statuses in hematopoietic precursors is related to the hematopoietic potential of pre-HSCs and the depletion of the Atg5 (autophagy related 5) gene specifically in endothelial cells impaired in the transition of endothelial to pre-HSCs, by hampering the autophagic process, likely via the NCL (nucleolin) pathway.Abbreviation: Atg5: autophagy related 5; EGFP: enhanced green fluorescent protein; EHT: endothelial-to-hematopoietic transition; HEC: hemogenic endothelial cell; HSC: hematopoietic stem cell; NCL: nucleolin; RFP: red fluorescent protein.

Autophagy regulates the maturation of hematopoietic precursors in the embryo.

An understanding of the mechanisms regulating embryonic hematopoietic stem cell (HSC) development would facilitate their regeneration. The aorta-gonad-mesonephros region is the site for HSC production from hemogenic endothelial cells (HEC). While several distinct regulators are involved in this process, it is not yet known whether macroautophagy (autophagy) plays a role in hematopoiesis in the pre-liver stage. Here, we show that different states of autophagy exist in hematopoietic precursors and correlate with hematopoietic potential based on the LC3-RFP-EGFP mouse model. Deficiency of autophagy-related gene 5 (Atg5) specifically in endothelial cells disrupts endothelial to hematopoietic transition (EHT), by blocking the autophagic process. Using combined approaches, including single-cell RNA-sequencing (scRNA-seq), we have confirmed that Atg5 deletion interrupts developmental temporal order of EHT to further affect the pre-HSC I maturation, and that autophagy influences hemogenic potential of HEC and the formation of pre-HSC I likely via the nucleolin pathway. These findings demonstrate a role for autophagy in the formation/maturation of hematopoietic precursors.

N-3 polyunsaturated fatty acids protect esophageal epithelial cells from acid exposure.

Our previous study showed that n-3 PUFAs inhibited inflammation in rats with esophagitis. This study aimed to observe the protective effect of n-3 PUFAs against acid damage to esophageal epithelial cells (Het-1A cells) and to explore its mechanism. The level of malondialdehyde (MDA) was increased by acid exposure, while that of superoxide dismutase (SOD) was decreased. In groups with different ratios of n-6/n-3 PUFAs, the expression levels of nuclear factor E2 related factor 2 (Nrf2) and SOD were increased with increasing proportions of n-3 PUFAs and were highest in the 1:1 group. Compared with those in the 9:1 group, the expression of NOD like receptor pyrin domain-containing protein 3 (NLRP3) and caspase-1 and the pyroptosis rate in the 1:1 group were decreased. Intervention with an Nrf2 agonist increased the expression of Nrf2 and decreased the expression of NLRP3 and caspase-1 and the pyroptosis rate. However, inhibiting Nrf2 expression led to the opposite result. In conclusion, n-3 PUFAs protected esophageal epithelial cells from acid damage by upregulating Nrf2 expression, which disrupted oxidative stress and NLRP3 inflammasome activation and inhibited pyroptosis.