Role of TSPO/VDAC1 Upregulation and Matrix Metalloproteinase-2 Localization in the Dysfunctional Myocardium of Hyperglycaemic Rats.

Micaela Gliozzi,Stefano Ruga,Ernesto Palma,Federica Scarano,Annamaria Tavernese,Lorenza Guarnieri,Vincenzo Musolino,Saverio Nucera,Rocco Mollace,Anna Rita Coppoletta,Roberta Macrì,Cristina Carresi,Vincenzo Mollace,Maria Caterina Zito,Miriam Scicchitano,Caterina Nicita,Jessica Maiuolo,Carolina Muscoli,Francesca Bosco

doi:10.3390/ijms21207432

Abstract

Clinical management of diabetic cardiomyopathy represents an unmet need owing to insufficient knowledge about the molecular mechanisms underlying the dysfunctional heart. The aim of this work is to better clarify the role of matrix metalloproteinase 2 (MMP-2) isoforms and of translocator protein (TSPO)/voltage-dependent anion-selective channel 1 (VDAC1) modulation in the development of hyperglycaemia-induced myocardial injury. Hyperglycaemia was induced in Sprague-Dawley rats through a streptozocin injection (35 mg/Kg, i.p.). After 60 days, cardiac function was analysed by echocardiography. Nicotinamide Adenine Dinucleotide Phosphate NADPH oxidase and TSPO expression was assessed by immunohistochemistry. MMP-2 activity was detected by zymography. Superoxide anion production was estimated by MitoSOX™ staining. Voltage-dependent anion-selective channel 1 (VDAC-1), B-cell lymphoma 2 (Bcl-2), and cytochrome C expression was assessed by Western blot. Hyperglycaemic rats displayed cardiac dysfunction; this response was characterized by an overexpression of NADPH oxidase, accompanied by an increase of superoxide anion production. Under hyperglycaemia, increased expression of TSPO and VDAC1 was detected. MMP-2 downregulated activity occurred under hyperglycemia and this profile of activation was accompanied by the translocation of intracellular N-terminal truncated isoform of MMP-2 (NT-MMP-2) from mitochondria-associated membrane (MAM) into mitochondria. In the onset of diabetic cardiomyopathy, mitochondrial impairment in cardiomyocytes is characterized by the dysregulation of the different MMP-2 isoforms. This can imply the generation of a “frail” myocardial tissue unable to adapt itself to stress.

Highlights

Diabetic cardiomyopathy (DCM) represents a complication of diabetes and is a relevant cause of hospitalization and mortality among affected patients
Our results show a down-regulation of secreted matrix metalloproteinase 2 (MMP-2) in the normal pellet diet (NPD) + STZ group as compared with the control, which was ablated after calcium chelation, suggesting that the hypothesized enhancement of cytosolic calcium triggered the down-regulation of active Matrix metalloproteinases (MMPs)-2, via membrane-associated MMPs (MT-MMP) overexpression
Clinical management of diabetic cardiomyopathy represents an untargeted goal in therapy because of poor understanding related to the molecular mechanisms underlying the impairment of heart structure and function

Summary

Introduction

Diabetic cardiomyopathy (DCM) represents a complication of diabetes and is a relevant cause of hospitalization and mortality among affected patients. Clinical data show that ventricular hypertrophy as well as diastolic and systolic dysfunction are the main detrimental events occurring as a result of chronic hyperglycaemia, even in those patients with well-controlled blood glycaemic levels [1,2,3]. The emerging role of dysfunctional mitochondria in the onset and development of DCM suggest that the intracellular levels of reactive oxygen species (ROS) are tightly correlated with the entity of myocardial damage. In hyperglycaemia-induced cardiovascular complications, NADPH oxidase represents the main source of mitochondrial O2−, which is a fundamental regulator in the formation of transition pore. The O2− amount can mediate the association between 18 kDa translocator protein (TSPO) and voltage-dependent anion-selective channel 1 (VDAC1), in order to prevent mitochondrial dysfunction or to promote apoptosis [8]

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Conclusion