Angiotensin-converting enzyme insertion/deletion gene polymorphism and interferon-β treatment response in multiple sclerosis patients: a preliminary report

We investigated the effect of the functional insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene on the response to interferon-β (IFN-β) therapy in Croatian and Slovenian patients with multiple sclerosis (MS). A total of 275 IFN-β treated MS patients [162 responders (Rs) and 113 nonresponders (NRs)] were genotyped by PCR. The ACE I/D genotype distribution and allele frequencies did not differ between female Rs and NRs. However, male NRs tended to have a greater prevalence of the DD genotype (P=0.073; odds ratio: 2.64; 95% confidence interval: 0.91-7.60) and a significantly higher frequency of the D allele (P=0.022; odds ratio: 2.43; 95% confidence interval: 1.13-5.20) than male Rs. Multiple forward stepwise regression analysis indicated that the negative response to IFN-β therapy was associated with the ACE-DD genotype in men (β=0.371; multiple R change: 0.132; P=0.009) and a higher pretreatment relapse rate in both men (β=-0.438; multiple R change: 0.135; P=0.015) and women (β=-0.208; multiple R change: 0.042; P=0.034). The ACE I/D polymorphism and pretreatment relapse rate accounted for ∼26.7% of the IFN-β response variability among the men in the sample. Further studies of a larger number of MS patients from different populations are necessary to evaluate these preliminary findings.

Macrophages in neuroinflammation: role of the renin-angiotensin-system

Macrophages are essential players of the innate immune system which are involved in the initiation and progression of various inflammatory and autoimmune diseases including neuroinflammation. In the past few years, it has become increasingly clear that the regulation of macrophage responses by the local tissue milieu is also influenced by mediators which were first discovered as regulators in the nervous or also cardiovascular system. Here, the renin-angiotensin system (RAS) is a major focus of current research. Besides its classical role in blood pressure control, body fluid, and electrolyte homeostasis, the RAS may influence (auto)immune responses, modulate T cells, and particularly act on macrophages via different signaling pathways. Activation of classical RAS pathways including angiotensin (Ang) II and AngII type 1 (AT₁R) receptors may drive pro-inflammatory macrophage responses in neuroinflammation via regulation of chemokines. More recently, alternative RAS pathways were described, such as binding of Ang-(1-7) to its receptor Mas. Signaling via Mas pathways may counteract some of the AngII/AT₁R-mediated effects. In macrophages, the Ang-(1-7)/Mas exerts beneficial effects on neuroinflammation via modulating macrophage polarization, migration, and T cell activation in vitro and in vivo. These data delineate a pivotal role of the RAS in inflammation of the nervous system and identify RAS modulation as a potential new target for immunotherapy with a special focus on macrophages.

Modulation of the kallikrein/kinin system by the angiotensin-converting enzyme inhibitor alleviates experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Bradykinin is the end-product of the kallikrein/kinin system, which has been recognized as an endogenous target for combating CNS inflammation. Angiotensin-converting enzyme (ACE) inhibitors influence the kallikrein/kinin system and reportedly have immunomodulatory characteristics. The objectives of this study were to determine whether bradykinin is involved in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of MS, and whether bradykinin control by the ACE inhibitor could be a therapeutic target in MS. The ACE inhibitor enalapril (1·0 or 0·2 mg/kg/day) was administered orally to EAE mice and the serum levels of bradykinin and cytokines in EAE mice were analysed. As a result, the administration of enalapril increased serum bradykinin levels, decreased the clinical and pathological severity of EAE and attenuated interleukin-17-positive cell invasion into the CNS. Additionally, bradykinin receptor antagonist administration reduced the favourable effects of enalapril. Our results suggest that bradykinin is involved in the pathomechanism underlying CNS inflammation in EAE, possibly through inhibiting cell migration into CNS. Control of the kallikrein/kinin system using ACE inhibitors could be a potential therapeutic strategy in MS.