Targeting the calpain/calpastatin system as a new strategy to prevent cardiovascular remodeling in angiotensin II-induced hypertension.

In hypertension, angiotensin (Ang) II is a critical mediator of cardiovascular remodeling, whose prominent features include myocardial and vascular media hypertrophy, perivascular inflammation, and fibrosis. The signaling pathways responsible for these alterations are not completely understood. Here, we investigated the importance of calpains, calcium-dependent cysteine proteases. We generated transgenic mice constitutively expressing high levels of calpastatin, a calpain-specific inhibitor. Chronic infusion of Ang II led to similar increases in systolic blood pressure in wild-type and transgenic mice. In contrast, compared with wild-type mice, transgenic mice displayed a marked blunting of Ang II-induced hypertrophy of left ventricle. Ang II-dependent vascular remodeling, ie, media hypertrophy and perivascular inflammation and fibrosis, was also limited in both large arteries (aorta) and small kidney arteries from transgenic mice as compared with wild type. In vitro experiments using vascular smooth muscle cells showed that calpastatin transgene expression blunted calpain activation by Ang II through epidermal growth factor receptor transactivation. In vivo and in vitro models of inflammation showed that impaired recruitment of mononuclear cells in transgenic mice was attributable to a decrease in both the release of and the chemotactic response to monocyte chemoattractant protein-1. Finally, results from collagen synthesis assay and zymography suggested that limited fibrogenesis was attributable to a decrease in collagen deposition rather than an increase in collagen degradation. These results indicate a critical role for calpains as downstream mediators in Ang II-induced cardiovascular remodeling and, thus, highlight an attractive therapeutic target.

Invariant and noninvariant natural killer T cells exert opposite regulatory functions on the immune response during murine schistosomiasis.

CD1d-restricted natural killer T (NKT) cells represent a heterogeneous population of innate memory immune cells expressing both NK and T-cell markers distributed into two major subsets, i.e., invariant NKT (iNKT) cells, which express exclusively an invariant T-cell receptor (TCR) alpha chain (Valpha14Jalpha18 in mice), and non-iNKT cells, which express more diverse TCRs. NKT cells quickly produce Th1- and/or Th2-type cytokines following stimulation with glycolipid antigen (Ag) and, through this property, play potent immunoregulatory roles in autoimmune diseases, cancer, and infection. No study has addressed the role of NKT cells in metazoan parasite infections so far. We show that during murine schistosomiasis, the apparent frequency of both iNKT cells and non-iNKT cells decreased in the spleen as early as 3 weeks postinfection (p.i.) and that both populations expressed a greater amount of the activation marker CD69 at 6 weeks p.i., suggesting an activated phenotype. Two different NKT-cell-deficient mouse models, namely, TCR Jalpha18-/- (exclusively deficient in iNKT cells) and CD1d-/- (deficient in both iNKT and non-iNKT cells) mice, were used to explore the implication of these subsets in infection. We show that whereas both iNKT and non-iNKT cells do not have a major impact on the immune response during the early phase (1 and 4 weeks) of infection, they exert important, although opposite, effects on the immune response during the acute phase of the disease (7 and 12 weeks), after schistosome egg production. Indeed, iNKT cells contribute to Th1 cell differentiation whereas non-iNKT cells might be mostly implicated in Th2 cell differentiation in response to parasite Ag. Our findings suggest, for the first time, that helminths activate both iNKT and non-iNKT cells in vivo, enabling them to differentially influence the Th1/Th2 balance of the immune response.

Unconventional strategies for the suppression of allergic asthma.

Allergic asthma results from an intrapulmonary allergen-driven Th2 response and is characterized by intermittent airway obstruction, airway hyperreactivity, and airway inflammation. An inverse association between allergic asthma and microbial infections has been observed. And this observation constitutes the base of the hygiene hypothesis. Here we discuss the hygiene hypothesis with emphasis on regulatory cells. We review the evidence for the emergence of regulatory cells, such as CD4(+)CD25(+) T cells during infection or during induction of tolerance by mucosal antigen administration. The review focuses also on the emergence of activated CD8(+) T cells and macrophages, induced by infections or microbial products, which also can result in the suppression of asthma. The underlying mechanisms by which regulatory immune cells suppress asthma may represent novel unconventional strategies controlling asthma.

Cutting edge: invariant V alpha 14 NKT cells are required for allergen-induced airway inflammation and hyperreactivity in an experimental asthma model.

Airway hyperreactivity (AHR), eosinophilic inflammation with a Th2-type cytokine profile, and specific Th2-mediated IgE production characterize allergic asthma. In this paper, we show that OVA-immunized Jalpha18(-/-) mice, which are exclusively deficient in the invariant Valpha14(+) (iValpha14), CD1d-restricted NKT cells, exhibit impaired AHR and airway eosinophilia, decreased IL-4 and IL-5 production in bronchoalveolar lavage fluid, and reduced OVA-specific IgE compared with wild-type (WT) littermates. Adoptive transfer of WT iValpha14 NKT cells fully reconstitutes the capacity of Jalpha18(-/-) mice to develop allergic asthma. Also, specific tetramer staining shows that OVA-immunized WT mice have activated (CD69(+)) iValpha14 NKT cells. Importantly, anti-CD1d mAb treatment blocked the ability of iValpha14 T cells to amplify eosinophil recruitment to airways, and both Th2 cytokine and IgE production following OVA challenge. In conclusion, these findings clearly demonstrate that iValpha14 NKT cells are required to participate in allergen-induced Th2 airway inflammation through a CD1d-dependent mechanism.