Host-parasite interactions and their outcome constitute a critical and challenging step in disease establishment in cutaneous leishmaniasis. In the present in vitro study we investigated the possible modulating effects of both sensory and autonomic neuropeptides that normally exist in human and mouse skin, on the uptake and leishmanicidal capacity of macrophages on Leishmania (L.) major parasites, using a monocyte/macrophage murine cell line (Raw 264.7). The sensory neuropeptides somatostatin (SOM), calcitonin gene-related peptide (CGRP) and substance P (SP) suppressed the macrophage capacity for phagocytosing L. major promastigotes at different concentrations, 10(-10) - 10(-5) M, however, the suppressive effect of SP does not reach a significant level. CGRP and SP enhanced the leishmanicidal capacity of macrophages at 10(-7) M, and 10(-5) M, respectively, whereas SOM was without effect. The autonomic neuropeptides vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) both suppressed the phagocytic and leishmanicidal capacities of macrophages at various concentrations, 10(-10) - 10(-5) M. The findings indicate that neuropeptides have modulating effects on macrophage-L. major interactions. These effects might be exerted by a direct action on macrophages or indirectly through induction of other mediators.

Ahmed AA, Wahbi A, Nordlind K, Kharazmi A, Sundqvist K-G, Mutt V, Lidén S. In Vitro Leishmania major Promastigote-Induced Macrophage Migration is Modulated by Sensory and Autonomic Neuropeptides. Scand J Immunol 1998;48:79-85 Recruitment, migration and adherence of macrophages and their interaction with inoculated promastigotes are key steps in the initiation of the inflammatory process in cutaneous leishmaniasis. Parasite-and nervous system-derived factors might be involved in this process. In the present study the chemotactic activities of live, killed and sonicated Leishmania major promastigotes and of the promastigote culture supernatant as well as the L. major surface protease gp63 towards a murine macrophage cell line, Raw 264.7, were investigated, using the Boyden technique. The sensory neuropeptides SOM, CGRP and SP, and the autonomic neuropeptides VIP and NPY, were also investigated for possible modulatory effects on this chemotaxis, using the living promastigotes. Living promastigotes were the most efficient attractants for macrophages compared with other forms of the parasites. Prior incubation of the macrophages with the parasites completely abolished the chemotactic activity. This might indicate that the living promastigote chemotaxis is a receptor-mediated process. On the other hand, paraformaldehyde-killed promastigotes not only failed to induce macrophage chemotaxis but also inhibited it in comparison with the control. The surface protease gp63 tended to inhibit the macrophage chemotactic activity and the sonicate tended to stimulate it compared with controls. The culture supernatant had no effect, indicating that the chemoattractive factors putatively synthesized by the living promastigotes are not released to the surrounding medium. Somatostatin inhibited L. major promastigoteinduced macrophage migration at a high concentration, 10 ¹6 M, while substance P inhibited it at both low concentrations, 10 ¹10 and 10 ¹9 M, and a high one, 10 ¹6 M, the last-mentioned having the greatest inhibitory effect. A stimulatory effect of calcitonin gene-related peptide was found at high concentrations, 10 ¹5 and 10 ¹6 M. Vasoactive intestinal peptide stimulated macrophage chemotactic activity at both a high, 10 ¹5 M, and at a low, 10 ¹9 M, concentration, the same concentration at which neuropeptide Y exerted its maximum inhibitory effect.

Sequential biopsies from skin lesions induced by nickel sulphate and sodium lauryl sulphate, respectively, were investigated with respect to expression of extracellular matrix proteins and adhesion molecules on lymphocytes, endothelial cells, and keratinocytes. The majority of the infiltrating lymphocytes expressed VLA-4, LFA-1, CD44 and ICAM-1, a variable fraction expressed Leu-8 and VLA-5, and few or no cells were positive for VLA-1, VLA-2 and VLA-6. Noteworthy, was that the infiltrating cells showed a substantial amount of fibronectin but relatively small or negligible presence of laminin, collagen type IV, IgG, IgA, IgM, and albumin. The fibronectin was associated with cell bodies as well as the area surrounding infiltrating cells. The number of infiltrating cells was larger in biopsies from nickel-sulphate induced lesions and the infiltrates contained more fibronectin than biopsies from lesions induced by sodium lauryl sulphate. However, at the single-cell level, the expression of VLA antigens, LFA-1, CD44 and ICAM-1 was similar in both groups. The endothelial cells of skin biopsies from nickel-sulphate-induced lesions showed a stronger expression of VCAM-1, ELAM-1 and ICAM-1 compared to biopsies from sodium lauryl sulphate-induced lesions. In the biopsies from nickel sulphate-induced lesions, the keratinocytes showed a tendency to less VLA-6 expression. These results suggest that fibronectin plays a role in lymphocyte extravasation or extravascular lymphocyte migration.