Effect of recombinant human MG53 protein on tourniquet-induced ischemia-reperfusion injury in rat muscle

Muscle multiorgan crosstalk with MG53 as a myokine for tissue repair and regeneration

Through stress and injury to tissues, the cell membrane is damaged and can lead to cell death and a cascade of inflammatory events. Soluble factors that mitigate and repair membrane injury are important to normal homeostasis and are a potential therapeutic intervention for regenerative medicine. A myokine is a type of naturally occurring factors that come from muscle and have impact on remote organs. MG53, a tripartite motif-containing family protein, is such a myokine which has protective effects on lungs, kidneys, liver, heart, eye, and brain. Three mechanisms of action for the beneficial regenerative medicine potential of MG53 have been identified and consist of 1) repair of acute injury to the cellular membrane, 2) anti-inflammatory effects associated with chronic injuries, and 3) rejuvenation of stem cells for tissue regeneration. As such, MG53 has the potential to be a novel and effective regeneration medicine therapeutic.

Cardiac effects and clinical applications of MG53

Heart disease remains the leading cause of mortality globally, so further investigation is required to identify its underlying mechanisms and potential targets for treatment and prevention. Mitsugumin 53 (MG53), also known as TRIM72, is a TRIM family protein that was found to be involved in cell membrane repair and primarily found in striated muscle. Its role in skeletal muscle regeneration and myogenesis has been well documented. However, accumulating evidence suggests that MG53 has a potentially protective role in heart tissue, including in ischemia/reperfusion injury of the heart, cardiomyocyte membrane injury repair, and atrial fibrosis. This review summarizes the regulatory role of MG53 in cardiac tissues, current debates regarding MG53 in diabetes and diabetic cardiomyopathy, as well as highlights potential clinical applications of MG53 in treating cardiac pathologies.

The Pivotal Role of Mitsugumin 53 in Cardiovascular Diseases

The MG53 (also known as TRIM72) is a conserved, muscle-specific tripartite motif family protein that is abundantly expressed in cardiac or skeletal muscle and present in circulation. Recently, the MG53 had been hypothesized to serve a dual role in the heart: involving in repairing cell membranes that protect myocardial function while acting as an E3 ligase to trigger insulin resistance and cardiovascular complications. This review discusses the roles of MG53 in cardiac physiological function with emphasis on MG53 protective function in the heart and its negative impact on the myocardium due to the continuous elevation of MG53. Besides, this work reviewed the significance of MG53 as a potential therapeutic in human cardiovascular diseases. Despite the expression of MG53 being rare in the human, thus exogenous MG53 can potentially be a new treatment for human cardiovascular diseases. Notably, the specific mechanism of MG53 in cardiovascular diseases remains elusive.

Enhancing membrane repair increases regeneration in a sciatic injury model

Various injuries to the neural tissues can cause irreversible damage to multiple functions of the nervous system ranging from motor control to cognitive function. The limited treatment options available for patients have led to extensive interest in studying the mechanisms of neuronal regeneration and recovery from injury. Since many neurons are terminally differentiated, by increasing cell survival following injury it may be possible to minimize the impact of these injuries and provide translational potential for treatment of neuronal diseases. While several cell types are known to survive injury through plasma membrane repair mechanisms, there has been little investigation of membrane repair in neurons and even fewer efforts to target membrane repair as a therapy in neurons. Studies from our laboratory group and others demonstrated that mitsugumin 53 (MG53), a muscle-enriched tripartite motif (TRIM) family protein also known as TRIM72, is an essential component of the cell membrane repair machinery in skeletal muscle. Interestingly, recombinant human MG53 (rhMG53) can be applied exogenously to increase membrane repair capacity both in vitro and in vivo. Increasing the membrane repair capacity of neurons could potentially minimize the death of these cells and affect the progression of various neuronal diseases. In this study we assess the therapeutic potential of rhMG53 to increase membrane repair in cultured neurons and in an in vivo mouse model of neurotrauma. We found that a robust repair response exists in various neuronal cells and that rhMG53 can increase neuronal membrane repair both in vitro and in vivo. These findings provide direct evidence of conserved membrane repair responses in neurons and that these repair mechanisms can be targeted as a potential therapeutic approach for neuronal injury.

Downregulation of miR-3568 Protects Against Ischemia/Reperfusion-Induced Cardiac Dysfunction in Rats and Apoptosis in H9C2 Cardiomyocytes Through Targeting TRIM62

microRNA-3568 (miR-3568) has been reported to be associated with atherosclerosis. Only few data describe the expression and underlying mechanism of miR-3568 in regulating cardiac ischemia-reperfusion (I/R) injury such as apoptosis. In this study, we therefore sought to investigate the potential function of miR-3568 in simulated I/R-induced apoptosis in H9C2 cardiomyocytes and related signaling pathways involved. Flow cytometry was performed to examine the cell apoptosis. The expression of miR-3568, Survivin, Bcl-2, ERK, JNK, p38, AKT, and STAT3 was measured by western blot and quantitative real-time PCR. The correlation between TRIM62 and p-STAT3 was measured by co-immunoprecipitation and ubiquitination. We found that miR-3568 expression in simulated I/R-induced H9C2 cardiomyocytes was increased in a time-dependent manner. miR-3568 mimic transfection in H9C2 cardiomyocytes significantly enhanced cell apoptosis, decreased the expression of Bcl-2 and Survivin, and activated STAT3 signaling, which were reversed by miR-3568 inhibitor. The direct interaction between miR-3568 and the 3'-untranslated region (UTR) of TRIM62 mRNA was confirmed by dual-luciferase reporter assay. TRIM62 overexpression or AG490, a selective inhibitor of JAK2/STAT3 significantly, significantly inhibited I/R and miR-3568 mimic induced cell apoptosis and STAT3 activation. TRIM62 was found to interact with and induce ubiquitination of p-STAT3. The facilitating role of miR-3568 in I/R injury was also observed in our in vivo rat models. In conclusion, our study suggests that miR-3568 promotes simulated I/R-induced apoptosis in H9C2 cardiomyocytes through targeting TRIM62.

Fresh whole blood resuscitation does not exacerbate skeletal muscle edema and long-term functional deficit after ischemic injury and hemorrhagic shock

BACKGROUND

Hemorrhagic shock caused by extremity vascular injuries is common in combat injuries. Fluid resuscitation is the standard treatment for severe hemorrhage (HEM). Tourniquets (TKs) used for HEM control cause ischemia-reperfusion (I/R) injury that induces edema formation in the injured muscle. Resuscitation fluids affect edema formation; however, its effect on long-term functional response remains unknown. The objectives of this study are to (1) compare acute muscle damage; (2) determine long-term functional recovery of ischemic muscle; and (3) compare local and systemic inflammatory response including the expression of junctional proteins following early resuscitation with Hextend and fresh whole blood using a rodent model of combined HEM and TK-induced limb I/R.

METHODS

Anesthetized Sprague-Dawley rats underwent 42.5% arterial HEM, followed by 3 hours of TK application. Animals were either not resuscitated or resuscitated with Hextend or fresh whole blood. Two time points were evaluated, 2 and 28 days. Plasma cytokine concentrations were determined at baseline and end resuscitation. At 2 days, edema formation, expression of junctional proteins, and tissue level cytokines concentrations were evaluated. At 28 days, in vivo muscle contractile properties were determined. At both time points, routine histology was performed and graded using a semiquantitative grading system.

RESULTS

All animals developed hemorrhagic hypovolemia; the mortality rate was 100% in nonresuscitated rats. Hextend resuscitation exacerbated muscle edema (~11%) and muscle strength deficit (~20%). Fresh whole blood resuscitation presented edema and muscle strength akin to TK only. Fresh whole blood resuscitation upregulated expression of junctional proteins including proangiogenic factors and dampened the inflammatory response.

CONCLUSION

Fresh whole blood resuscitation does not exacerbate either TK-induced edema or muscle strength deficit. Fresh whole blood resuscitation may reduce both acute and long-term morbidity associated with extremity trauma. To our knowledge, this is the first study to demonstrate the nature of the resuscitation fluid administered following HEM impacts short- and long-term indices of I/R in skeletal muscle.

An MG53-IRS1-interaction disruptor ameliorates insulin resistance

Mitsugumin 53 (MG53) is an E3 ligase that induces insulin receptor substrate-1 (IRS-1) ubiquitination and degradation in skeletal muscle. We previously demonstrated that the pharmaceutical disruption of the MG53-IRS-1 interaction improves insulin sensitivity by abrogating IRS-1 ubiquitination and increasing IRS-1 levels in C2C12 myotubes. Here, we developed a novel MG53-IRS-1 interaction disruptor (MID-00935) that ameliorates insulin resistance in diet-induced obese (DIO) mice. MID-00935 disrupted the molecular interaction of MG53 and IRS-1, abrogated MG53-induced IRS-1 ubiquitination and degradation and improved insulin signaling in C2C12 myotubes. Oral administration of MID-00935 increased insulin-induced IRS-1, Akt, and Erk phosphorylation via increasing IRS-1 levels in the skeletal muscle of DIO mice. In DIO mice, MID-00935 treatment lowered fasting blood glucose levels and improved glucose disposal in glucose and insulin tolerance tests. These results suggest that MID-00935 may be a potential muscle-targeting drug candidate for treating insulin resistance.

Co-delivery of a laminin-111 supplemented hyaluronic acid based hydrogel with minced muscle graft in the treatment of volumetric muscle loss injury

Minced muscle autografting mediates de novo myofiber regeneration and promotes partial recovery of neuromuscular strength after volumetric muscle loss injury (VML). A major limitation of this approach is the availability of sufficient donor tissue for the treatment of relatively large VMLs without inducing donor site morbidity. This study evaluated a laminin-111 supplemented hyaluronic acid based hydrogel (HA+LMN) as a putative myoconductive scaffolding to be co-delivered with minced muscle grafts. In a rat tibialis anterior muscle VML model, delivery of a reduced dose of minced muscle graft (50% of VML defect) within HA+LMN resulted in a 42% improvement of peak tetanic torque production over unrepaired VML affected limbs. However, the improvement in strength was not improved compared to a 50% minced graft-only control group. Moreover, histological analysis revealed that the improvement in in vivo functional capacity mediated by minced grafts in HA+LMN was not accompanied by a particularly robust graft mediated regenerative response as determined through donor cell tracking of the GFP+ grafting material. Characterization of the spatial distribution and density of macrophage and satellite cell populations indicated that the combination therapy damps the heightened macrophage response while re-establishing satellite content 14 days after VML to a level consistent with an endogenously healing ischemia-reperfusion induced muscle injury. Moreover, regional analysis revealed that the combination therapy increased satellite cell density mostly in the remaining musculature, as opposed to the defect area. Based on the results, the following salient conclusions were drawn: 1) functional recovery mediated by the combination therapy is likely due to a superposition of de novo muscle fiber regeneration and augmented repair of muscle fibers within the remaining musculature, and 2) The capacity for VML therapies to augment regeneration and repair within the remaining musculature may have significant clinical impact and warrants further exploration.

Plasma membrane wounding and repair in pulmonary diseases

Various pathophysiological conditions such as surfactant dysfunction, mechanical ventilation, inflammation, pathogen products, environmental exposures, and gastric acid aspiration stress lung cells, and the compromise of plasma membranes occurs as a result. The mechanisms necessary for cells to repair plasma membrane defects have been extensively investigated in the last two decades, and some of these key repair mechanisms are also shown to occur following lung cell injury. Because it was theorized that lung wounding and repair are involved in the pathogenesis of acute respiratory distress syndrome (ARDS) and idiopathic pulmonary fibrosis (IPF), in this review, we summarized the experimental evidence of lung cell injury in these two devastating syndromes and discuss relevant genetic, physical, and biological injury mechanisms, as well as mechanisms used by lung cells for cell survival and membrane repair. Finally, we discuss relevant signaling pathways that may be activated by chronic or repeated lung cell injury as an extension of our cell injury and repair focus in this review. We hope that a holistic view of injurious stimuli relevant for ARDS and IPF could lead to updated experimental models. In addition, parallel discussion of membrane repair mechanisms in lung cells and injury-activated signaling pathways would encourage research to bridge gaps in current knowledge. Indeed, deep understanding of lung cell wounding and repair, and discovery of relevant repair moieties for lung cells, should inspire the development of new therapies that are likely preventive and broadly effective for targeting injurious pulmonary diseases.

Plasma Membrane Repair: A Central Process for Maintaining Cellular Homeostasis

Plasma membrane repair is a conserved cellular response mediating active resealing of membrane disruptions to maintain homeostasis and prevent cell death and progression of multiple diseases. Cell membrane repair repurposes mechanisms from various cellular functions, including vesicle trafficking, exocytosis, and endocytosis, to mend the broken membrane. Recent studies increased our understanding of membrane repair by establishing the molecular machinery contributing to membrane resealing. Here, we review some of the key proteins linked to cell membrane repair.

Activity attenuates skeletal muscle fiber damage after ischemia and reperfusion

INTRODUCTION

In this investigation we aimed to determine whether: (1) physical activity protects rat skeletal muscle from ischemia/reperfusion (I/R) injury; and (2) continued activity after I/R improves the rate of healing.

METHODS

Rats were divided into sedentary or active (voluntary wheel running) groups. Active rats ran for 4 weeks before I/R or 4 weeks before plus 4 weeks after I/R.

RESULTS

Activity before I/R resulted in 73.2% less muscle damage (Evans blue dye inclusion). Sedentary and active rats had a similar decline in neural-evoked (∼ 99%) and directly stimulated (∼ 70%) in vivo muscle torque, and a similar reduction in junctophilin 1. Active rats produced 19% and 15% greater neural-evoked torque compared with sedentary rats at 14 and 28 days postinjury, respectively, although the rate of recovery appeared similar.

CONCLUSIONS

Activity protects against long-term muscle damage, but not short-term neural injury or excitation-contraction uncoupling. Continued activity neither accelerates nor hinders the rate of functional recovery.

Amelioration of ischemia-reperfusion-induced muscle injury by the recombinant human MG53 protein

INTRODUCTION

Ischemia-reperfusion injury (I-R) in skeletal muscle requires timely treatment.

METHODS

Rodent models of I-R injury were used to test the efficacy of recombinant human MG53 (rhMG53) protein for protecting skeletal muscle.

RESULTS

In a mouse I-R injury model, we found that mg53,-/- mice are more susceptible to I-R injury. rhMG53 applied intravenously to the wild-type mice protected I-R injured muscle, as demonstrated by reduced CK release and Evans blue staining. Histochemical studies confirmed beneficial effects of rhMG53. Of interest, rhMG53 did not protect against I-R injury in rat skeletal muscle. This was likely due to the fact that the plasma level of endogenous MG53 protein is high in rats.

CONCLUSIONS

Our data suggest that rhMG53 may be a potential therapy for protection against muscle trauma. A mouse model appears to be a better choice than a rat model for evaluating potential treatments for protecting skeletal muscle.