Cold exposure protects against medial arterial calcification development via autophagy

Diagnostic and prognostic significance of miR-320a-3p in patients with chronic heart failure

AIM

The purpose of this study was to investigate the diagnostic and prognostic value of miR-320a-3p in chronic heart failure (CHF).

METHODS

A total of 103 patients with CHF and 95 healthy controls were included in the study population. The expression level of serum miR-320a-3p was detected by qRT-PCR. The diagnostic effect of miR-320a-3p on CHF was evaluated by receiver operating characteristic curve. Kaplan-Meier curve and Cox regression were used to analyze the risk factors for 4-year prognosis of CHF patients. Bioinformatics analysis was used to analyze the possible target genes of miR-320a-3p and related signaling pathways.

RESULTS

Serum miR-320a-3p expression was increased in CHF patients, and the levels of BNP and LVEF were positively and negatively correlated with miR-320a-3p, respectively. The AUC value of ROC curve was 0.866, indicating that miR-320a-3p had high diagnostic accuracy for CHF. Survival curve and Cox analysis showed that high expression of miR-320a-3p was associated with poor prognosis in CHF patients, and age and miR-320a-3p were independent risk factors for prognosis in CHF patients. GO and KEGG analysis showed that the downstream target genes of miR-320a-3p were involved in biological processes such as cell adhesion, stem cell differentiation and neural development, and were enriched in mTOR, TNF, AMPK and other signaling pathways.

CONCLUSIONS

miR-320a-3p increased abnormally in CHF and was related to the severity of CHF. miR-320a-3p has the potential to be a diagnostic and prognostic marker for CHF.

Impaired autophagy following ex vivo cooling of simulated hypothermic temperatures in peripheral blood mononuclear cells from young and older adults

Hypothermia is a critical consequence of extreme cold exposure that increases the risk of cold-related injury and death in humans. While the initiation of cytoprotective mechanisms including the process of autophagy and the heat shock response (HSR) is crucial to cellular survival during periods of stress, age-related decrements in these systems may underlie cold-induced cellular vulnerability in older adults. Moreover, whether potential sex-related differences in autophagic regulation influence the human cold stress response remain unknown. We evaluated the effect of age and sex on mechanisms of cytoprotection (autophagy and the HSR) and cellular stress (apoptotic signaling and the acute inflammatory response) during ex vivo hypothermic cooling. Venous blood samples from 20 healthy young (10 females; mean [SD]: 22 [2] years) and 20 healthy older (10 females; 66 [5] years) adults were either isolated immediately (baseline) for peripheral blood mononuclear cells (PBMCs) or exposed to water bath temperatures maintained at 37, 35, 33, 31, or 4 °C for 90 min before PBMC isolation. Proteins associated with autophagy, apoptosis, the HSR, and inflammation were analyzed via Western blotting. Indicators of autophagic initiation and signaling (LC3, ULK1, and beclin-2) and the HSR (HSP90 and HSP70) increased when exposed to hypothermic temperatures in young and older adults (all p ≤ 0.007). Sex-related differences were only observed with autophagic initiation (ULK1; p = 0.015). However, despite increases in autophagic initiators ULK1 and beclin-2 (all p < 0.001), this was paralleled by autophagic dysfunction (increased p62) in all groups (all p < 0.001). Further, apoptotic (cleaved-caspase-3) and inflammatory (IL-6 and TNF-α) signaling increased in all groups (all p < 0.001). We demonstrated that exposure to hypothermic conditions is associated with autophagic dysfunction, irrespective of age or sex, although there may exist innate sex-related differences in cytoprotection in response to cold exposure as evidenced through altered autophagic initiation.

Molecular Mechanism of Calycosin Inhibited Vascular Calcification

Vascular calcification (VC) is a pathological condition frequently observed in cardiovascular diseases. Primary factors contributing to VC are osteogenic differentiation of vascular smooth muscle and hydroxyapatite deposition. Targeted autophagy (a lysosome-mediated mechanism for degradation/recycling of unnecessary cellular components) is a useful approach for inhibiting VC and promoting vascular cell health. Calycosin has been shown to alleviate atherosclerosis by enhancing macrophage autophagy, but its therapeutic effect on VC has not been demonstrated. Using an in vitro model (rat thoracic aortic smooth muscle cell line A7r5), we demonstrated effective inhibition of VC using calycosin (the primary flavonoid component of astragalus), based on the enhancement of autophagic flux. Calycosin treatment activated AMPK/mTOR signaling to induce initiation of autophagy and restored mTORC1-dependent autophagosome-lysosome fusion in late-stage autophagy by promoting soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex formation, thereby preventing stoppage of autophagy in calcified cells. Calycosin substantially reduced degrees of both osteogenic differentiation and calcium deposition in our VC cell model by enhancing autophagy. The present findings clarify the mechanism whereby calycosin mitigates autophagy stoppage in calcified smooth muscle cells and provide a basis for effective VC treatment via autophagy enhancement.