Dual immune effect of iNKT cells considering human cutaneous and visceral leishmaniasis: An example of cell plasticity according to different disease scenarios.

Although the semi-invariant natural killer T cells (iNKT) are a small subpopulation of cells in the peripheral blood, they are presumed to play a role in early stages of infection against various pathogens, including protozoa. This work investigates the activation status and cytokine profile of iNKT cells during human Leishmania infantum and Leishmania braziliensis infection. We studied iNKT cells in patients with symptomatic active visceral leishmaniasis (AVL) (n = 8), patients with symptomatic active cutaneous leishmaniasis (ACL) (n = 13), negative endemic controls (NEC) (n = 6) and non-endemic controls (NonEC) (n = 6), with and without total Leishmania antigen stimulus (TLA). The number of iNKT cells in the peripheral blood of patients with ACL and AVL unaltered in relation to control groups. Moreover, the iNKT cells from ACL showed a hyperactivation profile compared to patients with AVL. Additionally, TLA induced IFN-gamma production in iNKT cells from patients with ACL, while in iNKT of patients with AVL, TLA induced a decrease in this cytokine. Higher IL-17 and IL-10 production by iNKT cells from patients with ACL were also observed compared to all other groups. There were no changes in iNKT IL-10-producing cells in AVL after TLA stimulation. However, TLA induced increase in IL-10 in iNKT cells in patients with ACL. These findings suggest that, although iNKT cells showed distinct profiles in patients with ACL and AVL, they play a dual role in immune modulation in both Leishmania infections.

NO production and potassium channels activation induced by Crotalus durissus cascavella underlie mesenteric artery relaxation.

Animal toxins are natural resources for pharmacological studies. The venom of Crotalus durissus cascavella (C.d. cascavella) may be a source in the bio-prospecting of new anti-hypertensive agents. The aim of this study was to investigate vascular effects of the venom of C.d. cascavella in normotensive rats. Studies were performed using isolated mesenteric artery segments and aortic endothelial cells. The cumulative administration of the venom of C.d. cascavella (0.001-30 µg/mL) on phenylephrine (Phe; 10 µM) pre-contracted rings induced a concentration-dependent vasorelaxation in the presence of vascular endothelium (Emax = 47.9 ± 5.0% n = 8), and its effect was almost abolished in the absence of endothelium (Emax = 5.8± 2.4% n = 5 (∗∗∗p < 0.001)). Tissue viability was maintained as there was no difference in the contractile capacity of rings before and after the administration of venom. The vasorelaxant effect of the venom was also abolished when arteries were pre-contracted with potassium chloride (KCl; 80 mM) (Emax = 6.4± 0.9% n = 5, ∗∗∗p < 0.001). When assessing the participation of endothelium-derived relaxing factors, it was noted that non-selective COX inhibition with indomethacin (10 µM) caused a significant reduction in the vasorelaxant effect of C.d. cascavella (*p < 0.05). When investigating the participation of NO released by endothelium, there was a significant reduction of the vasorelaxant effect of venom in rings treated with L-NAME (100 µM; Emax = 17.5± 2.2% n = 6; **p < 0.01). Similar results were noted in the presence of ODQ (10 µM), an inhibitor of soluble guanylyl cyclase (Emax = 11.2± 3.5%, n = 6) and PTIO (100 µM), a stable radical scavenger for nitric oxide (Emax = 10.77± 3.6%, n = 6). Moreover, the venom induced the release of NO by isolated aortic endothelial cells through amperometric studies. When assessing the participation of K+ channels on the vasodilatory response of the venom, tyrode solution with 20 mM of KCl caused a significant reduction in the relaxation response (p < 0.001) (Emax = 21.3 ± 8%, n = 7), as did inhibitor of delayed rectifier K+ channels (4-amynopiridine 1 mM; Emax = 9.5 ± 1.3, %, n = 5, ***p < 0.001), and vasorelaxation was almost abolished in the presence of Iberiotoxin (IbTx 100 nM). Therefore, these results suggest that the venom of C.d. cascavella induces vasorelaxation in superior mesenteric artery rings of normotensive rats in an endothelium-dependent manner. Specifically, the venom stimulates the generation of endothelium-derived relaxing factors, especially NO, and activates vascular smooth muscle hyperpolarization through K+ channels. These data illustrate that C.d. cascavella is a source of bioactive molecules and therefore has therapeutic potential in the treatment of cardiovascular diseases such as hypertension.

Endothelium-derived nitric oxide is involved in the hypotensive and vasorelaxant effects induced by discretamine in rats.

The aim of this study was to investigate the pharmacological effects of discretamine, an isoquinoline alkaloid isolated from Duguetia magnolioidea Maas, on the cardiovascular system, using a combined in vivo and in vitro approach. Blood pressure and heart rate measurements, as well as changes in isometric tension in rat superior mesenteric arterial rings, elicited by discretamine were recorded. In normotensive non-anaesthetized rats (n = 6), discretamine (0.01; 0.05; 0.1; 0.5; 1, 5 and 10 mg/kg i.v., randomly) injections produced hypotension (-5.2 +/- 1.7; -5.1 +/- 2.1; -7.7 +/- 2; -8.9 +/- 1.7; -9.6 +/- 2.2; -16.8 +/- 2.8 and -13.4 +/- 1.3 mmHg, respectively) accompanied by tachycardia (24.2 +/- 6.1; 36.8 +/- 11.3; 44.2 +/- 7.7; 45.9 +/- 6.4; 48.2 +/- 9.1; 72.1 +/- 14.5 and 64 +/- 17 bpm, respectively). Hypotensive and tachycardic responses were significantly attenuated after L-NAME (20 mg/kg, i.v.) administration. In isolated rat mesenteric artery rings, with endothelium intact, discretamine (10(-12) - 10(-5) M) induced concentration-dependent relaxation of the contractions induced by phenylephrine (10 microM) [pD2 = 6.8 +/- 0.1]. The effect of the discretamine on phenylephrine induced contractions was significantly attenuated after removal of the vascular endothelium [pD2 = 5.8 +/- 0.04]. Similar results were obtained after pre-treatment with L-NAME 100 microM [pD2 = 5.8 +/- 0.04], L-NAME 300 microM [pD2 = 5.9 +/- 0.06], Hydroxocobalamin 30 microM [pD2 = 5.8 +/- 0.06] or ODQ 10 microM [pD2 = 5.8 +/- 0.04]. In addition, in rabbit aorta endothelial cell line, discretamine significantly increased NO3- levels. These results suggest that the hypotensive effect induced by discretamine is probably due to a peripheral vasodilatation, at least, in part, due to the release of NO from vascular endothelium and consequent activation of soluble guanylyl cyclase (GC) in the vascular smooth muscle cells.