MALAT1 regulates PCT expression in sepsis patients through the miR-125b/STAT3 axis

Procalcitonin (PCT) is an important marker in diagnosing sepsis. However, some other diseases can also cause an increase in PCT. PCT still has some limitations in the clinical application of diagnosing sepsis. Therefore, it is of great significance to clarify the regulatory mechanism of PCT expression in sepsis and provide new therapeutic targets for sepsis.

Blood samples from clinical patients were collected, and peripheral blood monocytes were isolated. Bioinformatics was performed to find the ceRNA regulatory network of STAT3/PCT. MALAT1 and miR-125b were detected by qRT-PCR. MALAT1 was located by fluorescence in situ hybridization (FISH) in U937 cells, and the regulatory relationship between MALAT1, miR-125b, and STAT3 was verified by double luciferase activity report and RNA pull-down assay. U937 cells were transfected with miR-125b, and the effects of the MALAT1/miR-125b/STAT3 pathway on gene and protein secretion levels of PCT were verified by qRT-PCR, western blot, and ELISA.

In the serum of sepsis patients and lipopolysaccharide(LPS)-induced U937 cells, MALAT1, STAT3, and PCT gene expression levels were significantly increased, while miR-125b expression level was decreased. FISH results showed that the MALAT1 transcript was mainly located in the nucleus. The double luciferase activity report and RNA pull-down assay results suggested a targeted regulatory relationship between MALAT1, miR-125b, and STAT3. LPS-induced U937 cells transfection with MALAT1 siRNA decreased STAT3 protein expression and phosphorylation level and the expression of PCT. Co-transfection with miR-125b inhibitor effectively reversed this phenomenon.

MALAT1 could upregulate the expressions of STAT3 and PCT by targeted adsorption of miR-125b.