CONICET | Buscador de Institutos y Recursos Humanos

Myocardial infarction (MI) is one of the leading causes of death worldwide. Prognosis and mortality rate are directly related to infarct size and post-infarction pathological heart remodeling, which can lead to heart failure. MI-affected areas are commonly recognized by hypoxic conditions, increasing the expression of hypoxia-inducible factor (HIF-1) which induces a reduction in the infarct size and improves cardiac function (S.H. Lee, 2000; M. Kido, 2005). Hypoxia translocates HIF-1 to the nucleus thereby activating numerous genes including the transcription of carbonic anhydrase IX (CAIX) gene car9. CAIX exerts a relevant function in regulating myocardial intracellular pH (pHi),critical for the normal heart performance. Thus, our objective was to investigate the participation of CAIX and its relationship with bicarbonate transporters (BT) and HIF-1 on cardiac remodeling in infarcted and non-infarcted areas of rats subjected to coronary artery ligation (LAD). Immunohistochemical studies revealed after 2 h of infarction an increase in HIF-1 levels about 4 times in respect to a remote area. Similarly, the expression of HIF-1 increased in cardiac tissue after 2 h of infarction (137 ± 13 vs 100 ± 3 % remote area) confirmed by immunoblotting. HIF-1 fluorescence intensity increased about 1.84 times in isolated cardiomyocytes subjected to 2 h hypoxia evidenced by confocal microscopy, with a nuclear distribution. Immunohistochemical studies showed an increase in the infarcted area at 2 h in CAIX levels about 30 times in respect to a remote area, mainly distributed throughout the cell and localized in the plasma membrane at 24 h. The expression of CAIX in cardiac tissue was increased after 2h of MI (141 ± 2 vs 100 ± 7 % remote area) by immunoblotting. We observed an increment of CAIX fluorescence intensity about 4 times in isolated cardiomyocytes exposed to 2 h of hypoxic conditions by confocal microscopy. NBC1 protein expression in cardiac tissue was increased after 2 h of infarction (150 ± 17 vs 100 ± 3 % remote area) by immunoblotting. CAIX and NBC1 interaction in infarcted cardiac tissue was analyzed, revealing an increase in the levels of NBC1 in cardiac tissue subjected to MI for 2h when CAIX is present (160 ± 15 vs 100 ± 3 % remote area) by immunoprecipitation. Through STRINGdatabase analysis (https://string-db.org), we examined HIF-1, CAIX, and NBC1 protein interaction. CAIX may improve the acid state of the ischemic zone by interacting with BTPs and, collaborating with other mechanisms trying to restore the pHi to its physiological value and promote cell survival. This result suggests that CAIX interacts with NBC1 in our infarct model, making it a promising therapeutic target.