Recombinant human mitsugumin 53(Rutgers State University of New Jersey/TRIM-edicine)

Chemotherapy drugs such as doxorubicin (DOX) are frequently used to treat cancer, but its negative impact on the heart reduces its effectiveness. Among the members of the TRIM protein family, mitsugumin (MG)53, also known as TRIM72, is unique. It is primarily present in the plasma membrane of cardiac and skeletal muscle cells and has been demonstrated to participate in mending cellular membrane damage while protecting against heart ischemia/reperfusion injury. This research investigated the role of MG53 in DOX-induced apoptosis using H9c2 cells, a cardiomyoblast cell line, as an experimental model. Our findings indicate that DOX treatment statistically significantly upregulates MG53 expression in H9c2 cells. Furthermore, MG53 overexpression exacerbated DOX-induced apoptosis, as confirmed by elevated levels of cleaved-caspase3 and BAX and reduced expression of Bcl-2. Flow cytometry analysis supported the elevated cell death rate in cells overexpressing MG53. Additionally, MG53 overexpression was associated with reduced phosphorylation levels of protein kinase B (AKT), as indicated by the decreased phosphorylation levels of AKT. Conversely, silencing MG53 through siRNA increased the phosphorylation levels of AKT. These results imply that MG53 exacerbates DOX-induced apoptosis, related to reduced AKT phosphorylation. Our investigation sheds light on the detrimental effects of MG53 in DOX-induced myocardial damage and underscores its potential as a therapeutic target for alleviating DOX treatment-related heart toxicity. SIGNIFICANCE STATEMENT: This study reveals that mitsugumin 53 exacerbates doxorubicin-induced apoptosis in H9c2 cells, associated with altered protein kinase B signaling. Targeting mitsugumin 53 may offer a novel therapeutic approach to mitigate doxorubicin-associated cardiotoxicity.

Septic cardiac dysfunction (SCD) is the most common complication of sepsis, which has become the primary cause of death in intensive care units. The muscle-specific protein mitsugumin-53 (MG53) has been identified to protect cell integrity as a "Molecular Band-Aid".

The recombinant human MG53 (rhMG53) pretreatment has been reported to prevent cardiac function damage caused by cecal ligation and puncture (CLP). However, whether or not MG53 protects against SCD remains to be further clarified.

C57BL/6J mice were intraperitoneally injected with lipopolysaccharide (LPS) to generate the SCD model. MG53 was overexpressed by intravenously injected adeno-associated virus, and the rhMG53 was administrated intraperitoneally. The cardiac function was evaluated by echocardiography, and the cardiac inflammation was assessed through ELISA and Western blot. The mechanisms of MG53 were studied by quantitative real-time PCR (qPCR) and co-immunoprecipitation (co-IP).

Our present study found that MG53 expression was lower in hearts from SCD mice than controls. Overexpression or exogenous MG53 treatment alleviated cardiac dysfunction, improved survival rate in SCD mice, accompanied with improved pathological changes, reduced cardiomyocyte apoptosis, and lowered inflammatory factor levels in serum or hearts. Mechanistically, MG53 inhibited TLR4 transcriptional activity by ubiquitinating ATF2, an essential transcriptional factor for TLR4, which ultimately reduced the expression of TLR4.

MG53 protect the cardiac function against sepsis by down-regulation of TLR4 expression, via ubiquitination of ATF2, a TLR4 transcriptional factor, which might be a promising therapeutic approach for septic cardiac dysfunction.