Estrogen‐dependent gene regulation: Molecular basis of TIMP‐1 as a sex‐specific biomarker for acute lung injury.

Increased circulating tissue inhibitor of metalloproteinases‐1 (TIMP‐1) levels have been observed in patients with acute lung injury (ALI). However, the sex‐specific regulation of TIMP‐1 and the underlying molecular mechanisms have not been well elucidated. In this study, we found that plasma TIMP‐1 levels were significantly higher in COVID‐19 and H1N1 patients compared with those in healthy subjects (n = 25). TIMP‐1 concentrations were significantly different between males and females in each disease group. Among female but not male patients, TIMP‐1 levels significantly correlated with the PaO2/FiO2 ratio and hospital length of stay. Using the mouse model of ALI induced by the H1N1 virus, we found that TIMP‐1 is strikingly induced in PDGFRα‐positive cells in the murine lungs. Moreover, female mice showed a higher Timp‐1 expression in the lungs on day 3 postinfection. Mechanistically, we observed that estrogen can upregulate TIMP‐1 expression in lung fibroblasts, not epithelial cells. In addition, overexpression of estrogen receptor α (ERα) increased the TIMP‐1 promoter activity. In summary, TIMP‐1 is an estrogen‐responsive gene, and its promoter activity is regulated by ERα. Circulating TIMP‐1 may serve as a sex‐specific marker, reflecting the severity and worst outcomes in female patients with SARS‐CoV2‐ and IAV‐related ALI. [ABSTRACT FROM AUTHOR]