Inflammation alters angiotensin converting enzymes (ACE and ACE-2) balance in rat heart

Angiotensin converting enzymes (ACE) and more recently discovered ACE-2 are important proteins involved in the renin-angiotensin system. The balance between ACE and ACE-2 is important for the regulation of blood pressure and electrolyte homeostasis. Inflammatory diseases like rheumatoid arthritis are associated with increased risk for cardiovascular complications. We studied the effect of inflammation on the expression levels of ACE and ACE-2 in two groups (n = 4/group) of adjuvant arthritis (AA) and healthy (control) rats. The AA group received 0.2 ml of 50 mg ml(-1) of Mycobacterium butyricum suspended in squalene into the tail base. On day 12, rats were euthanized and their organs (hearts, liver, kidney, and intestine) were excised. The mRNA of ACE and ACE-2 were determined by real-time polymerase chain reaction. ACE and ACE-2 protein expression in rat heart was determined by Western blot. Inflammation resulted in 80% reduction of ACE-2 gene expression in rat heart. ACE-2/ACE expression ratio was significantly reduced from 0.7 ± 0.4 in control rats to 0.07 ± 0.09 in AA. Similarly, ACE-2/ACE protein expression ratio was also disrupted with a significant reduction in AA animals (6.7 ± 4.8 vs. 0.9 ± 05 in control and AA, respectively). ACE-2 has been found to provide negative feedback of renin-angiotensin system and protection of the heart and kidneys. Disruption of the balance between ACE and ACE-2 observed in inflammation may be, at least in part, involved in the cardiovascular complications seen in patients with inflammatory diseases.