The role of neurotrophin polymorphisms and susceptibility to neural damage in leprosy

OBJECTIVES

Mycobacterium leprae is able to infect Schwann cells leading to neural damage. Neurotrophins are involved in nervous system plasticity and impact neural integrity during diseases. Investigate the association between single nucleotide polymorphisms in neurotrophin genes and leprosy phenotypes, especially neural damage.

DESIGN

We selected single nucleotide polymorphisms in neurotrophins or their receptors genes associated with neural disorders: rs6265 and rs11030099 of brain-derived neurotrophic factor (BDNF), rs6330 of BDNF, rs6332 in NT3 and rs2072446 of P75NTR. The association of genetic frequencies with leprosy phenotypes was investigated in a case-control study.

RESULTS

An association of the BDNF single nucleotide polymorphism rs11030099 with the number of affected nerves was demonstrated. The "AA+AC" genotypes were demonstrated to be protective against nerve impairment. However, this variation does not affect BDNF serum levels. BDNF is an important factor for myelination of Schwann cells and polymorphisms in this gene can be associated with leprosy outcome. Moreover, rs11030099 is located in the binding region for micro-RNA (miRNA) 26a that could be involved in control of BDNF expression. We demonstrated different expression levels of this miRNA in polar forms of leprosy.

CONCLUSION

Our findings demonstrate for the first time an association between the polymorphism rs11030099 in the BDNF gene and neural commitment in leprosy and may indicate a possible role of miRNA-26a acting synergistically to these genetic variants in neural damage development.

COX/iNOS dependence for angiotensin-II-induced endothelial dysfunction

Vascular dysfunction induced by angiotensin-II can result from direct effects on vascular and inflammatory cells and indirect hemodynamic effects. Using isolated and functional cultured aortas, we aimed to identify the effects of angiotensin-II on cyclooxygenase (COX) and inducible nitric oxide synthase (iNOS) and evaluate their impact on vascular reactivity. Aortic rings from mice were incubated overnight in culture medium containing angiotensin-II (100 nmol/L) or vehicle to induce vascular disfunction. Vascular reactivity of cultured arteries was evaluated in a bath chamber. Immunofluorescence staining for COX-1 and COX-2 was performed. Nitric oxide (NO) formation was approached by the levels of nitrite, a NO end product, and using a fluorescent probe (DAF). Oxidative and nitrosative stress were determined by DHE fluorescence and nitrotyrosine staining, respectively. Arteries cultured with angiotensin-II showed impairment of endothelium-dependent relaxation, which was reversed by the AT₁ receptor antagonist. Inhibition of COX and iNOS restored vascular relaxation, suggesting a common pathway in which angiotensin-II triggers COX and iNOS, leading to vasoconstrictor receptors activation. Moreover, using selective antagonists, TP and EP were identified as the receptors involved in this response. Endothelium-dependent contractions of angiotensin-II-cultured aortas were blunted by ibuprofen, and increased COX-2 immunostaining was found in the arteries, indicating endothelium release of vasoconstrictor prostanoids. Angiotensin-II induced increased reactive oxygen species and NO production. An iNOS inhibitor prevented NO enhancement and nitrotyrosine accumulation in arteries stimulated with angiotensin-II. These results confirm that angiotensin-II causes vascular inflammation that culminates in endothelial dysfunction in an iNOS and COX codependent manner.