Serum miRNA-122 in acute liver injury induced by kidney injury and sepsis in CD-1 mouse models.

Aim: miRNA-122 (miR-122) is a new, interesting liver injury biomarker but little is known about its effects when there is an indirect acute liver injury.

Methods: We investigated this by using indirect liver injury mice models with bilateral ureter obstruction (BUO), bilateral nephrectomy (BiNx) and cecal ligation and puncture (CLP). A direct liver injury model, liver ischemia/reperfusion injury (liver I/R), was performed in parallel. Liver injury (i.e. liver histology, alanine transaminase [ALT]), kidney damage (i.e. serum creatinine) and cytokines (i.e. tumor necrosis factor-α, interleukin [IL]-6, IL-1β, IL-10) were assessed.

Results: Six hours after BUO/BiNx/CLP, the ALT and serum cytokines were approximately 1.5-fold higher than the baseline whereas miR-122 did not change. After 6 h of BiNx, there were prominent hepatocyte vacuolization but no elevations of miR-122. However, after 24 h of BUO/BiNx/CLP, ALT, hepatocyte vacuolization and miR-122 increased. The cytokines at 6 h might have induced the production of miR-122 at 24 h. The results from the in vitro study with HepG2 cells and each of the cytokines resulted in increased miR-122. On the other hand, when the direct liver injury model was used, there was a fivefold and 22-fold increase in the ALT at 0.5 and 1 h after surgery, respectively, and high serum miR-122 which corroborated the results from the liver histopathology.

Conclusion: We demonstrated that prior serum cytokine accumulation increased serum miR-122 in indirect liver injury induced by BUO/BiNx and less severe sepsis mouse models. Cytokine accumulation may be responsible for miR-122 expression in these models. The clinical importance of liver injury demonstrated by the discordance between serum miR-122 and ALT was an interesting issue.