E-selectin and P-selectin expression in endothelium of leprosy skin lesions.

Leprosy is an infectious-contagious disease whose clinical evolution depends on the immune response pattern of the host. Adhesion molecules and leukocyte migration from blood to tissue are of the utmost importance for the recognition and elimination of infectious pathogens. Selectins are transmembrane glycoproteins that share a similar structural organization and can be divided into three types according to their site of expression. The biopsies were cut into 5µm thick sections and submitted to immunohistochemistry using antibodies against E-selectin and P-selectin. The number of E-selectin-positive cells was significantly higher in the tuberculoid form than in the lepromatous form. The immunostaining pattern of P-selectin differed from that of E-selectin. Analysis showed a larger number of endothelial cells expressing CD62P in the lepromatous form compared to the tuberculoid form. The presence of these adhesins in the endothelium contributing to or impairing the recruitment of immune cells to inflamed tissue and consequently influences the pattern of immune response and the clinical presentation of the disease.

Rifampicin inhibits the retinal neovascularization in vitro and in vivo.

Rifampicin, an antibacterial drug widely used in the treatment of tuberculosis and leprosy, has recently been reported to have anti-oxidative and anti-apoptotic effects. However, its anti-angiogenic effect has not been investigated. We examined its anti-angiogenic effect on tube formation and proliferation by human umbilical vein endothelial cells (HUVECs) in vitro and on retinal neovascularization in a murine oxygen-induced retinopathy model in vivo. In addition, we explored the potential mechanisms for its anti-angiogenic effect. Rifampicin significantly suppressed HUVEC tube formation and proliferation, and its effects appeared to be mediated at least in part through inhibition of extracellular signal-regulated kinase (ERK) 1/2 phosphorylation. Retinal neovasuclarization was induced in neonatal mice by returning the retina to normoxia (21% O2) after exposure to hyperoxia (75% O2) from postnatal day 7 (P7) to P12. Rifampicin was given subcutaneously at 20mg/kg once a day from immediately after hyperoxia (P12) to P16. At P17, flat-mounted retinas were prepared and evaluated for pathological and physiological angiogenesis. Rifampicin significantly suppressed retinal neovascularization (versus vehicle treatment), but revascularization of the capillary-free area did not differ between vehicle and rifampicin treatment. Rifampicin has anti-angiogenic effects in vitro and in vivo, and may be useful as an anti-angiogenic agent in the treatment of retinal neovascularization diseases.

Electron microscope appearance of lepromatous footpads of nude mice [corrected].

Footpad lesions of 3 nude mice infected by Mycobacterium leprae were studied at 9, 12, and 14 months after inoculation with light and electron microscope. The lesions were somewhat similar to those found in nodules in polar lepromatous leprosy. Striated muscles rather than nerves were the preferred site of the growth of M. leprae. Yet, M. leprae were identified in Schwann cells and endothelial cells, singly and in clumps. M. leprae filled macrophages, and free M. leprae were found in large numbers in the endoneurium without producing any significant demyelination.

Association of Mycobacterium leprae with human endothelial cells in vitro.

Endothelial cell infection by Mycobacterium leprae has long been described histologically in all types of leprosy and in some of the acute reactions occurring in this disease. Recent evidence from experimental lepromatous neuritis indicates that M. leprae colonizes endothelial cells of epineural blood vessels even in sites of minimal infection, suggesting that interaction between these cells and M. leprae may play an important role in the selective localization of this organism to peripheral nerve. To begin to study the mechanisms involved, we have examined the interaction between M. leprae and human umbilical vein endothelial cells (HUVEC) in vitro using light microscopy, scanning and transmission electron microscopy, and confocal laser scanning microscopy. When M. leprae were added to confluent monolayers of HUVEC, uptake increased slowly to a maximum at 24 hours. Maximal percentages of infected cells were similar at ratios of organisms:cell over a range of 25:1 to 100:1. The bacilli appeared to lie within membrane-bound vacuoles at all time points. The kinetics of association of M. leprae with HUVEC are much slower than has previously been observed with macrophages, possibly due to differences in the binding of M. leprae. Compared with other pathogens that infect endothelial cells, M. leprae also appear to be ingested more slowly, and to a more limited degree. The receptors involved in M. leprae binding to endothelial cells and the impact of intracellular infection by M. leprae on these cells remain to be determined.

Endothelial cells and the pathogenesis of lepromatous neuritis:insights from the armadillo model.

Selective infection of peripheral nerves is a unique property of Mycobacterium leprae that results in serious injury, but its basis is unexplained. Recent evidence from infected armadillos suggests that endothelial cells of peripheral nerve vasculature may be the gatekeepers by which M. leprae infects nerves. The pathogenesis of neuropathy in leprosy may thus entail a dynamic sequence of adhesion, immunologic, and inflammatory processes involving peripheral nerve endothelial cells.

M. leprae infection of vascular and lymphatic endothelial cells of the epineurium and perineurium in experimental lepromatous neuritis.

Infection of peripheral nerve by M. leprae, the histopathologic hallmark of leprosy, is a major factor in this disease, but the route and mechanisms by which bacilli localize to peripheral nerve are unknown. Experimentally infected armadillos have recently been recognized as a model of lepromatous neuritis; the major site of early accumulation of M. leprae is epineurial. To determine the epineurial cells involved, 1 cm. segments of 44 nerves from armadillos were screened for acid-fast bacilli (AFB), and thin sections were examined ultrastructurally. Of 596 blocks containing nerve, 36% contained AFB. Overall, M. leprae were found in endothelial cells in 40% of epineurial blood vessels and 75% of lymphatics, and in 25% of endoneurial vessels. Comparison of epineurial and endoneurial findings suggested that colonization of epineurial vessels preceded endoneurial infection. Such colonization of epineurial nutrient vessels may greatly increase the risk of endoneurial M. leprae bacteremia, and also enhance the risk of ischemia following even mild increases in inflammation or mechanical stress. These findings also raise the possibility that early, specific mechanisms in the localization of M. leprae to peripheral nerve may involve adhesion events between M. leprae (or M. leprae-parasitized macrophages) and the endothelial cells of the vasa nervorum.

The nose in leprosy: immunohistology of the nasal mucosa.

A detailed study of the nose was undertaken in 40 leprosy patients with different classifications of leprosy and different durations of disease at two hospitals in Brazil. This manuscript describes the immunohistochemical data on cellular infiltrates in the nasal biopsies of those patients. It was surprising that the damage to the whole depth of the nasal mucosa, epithelium and lamina propria was considerable, as was the case in the nasal mucosa which looked relatively normal during clinical inspection. The epithelium showed large holes which looked like very extended goblet cells. Very obvious was the lack of vasoconstriction after cocaine application, and the vessels also showed a lack of staining with factor VIII, possibly indicating a disruption of the endothelium. The number of neurofilaments was extensively reduced in all leprosy groups compared to normal controls. As in the skin, an increased number of CD68+ cells was found in the lamina propria of the nasal mucosa of the lepromatous patients. Contrary to findings in the skin, in the nasal mucosa of the borderline/lepromatous patients the number of CD4+ cells was increased and the number of CD8+ cells was decreased compared to normal controls. The number of CD8+ cells tended to be more reduced when the history of leprosy was longer. It is not clear as yet whether the reduced numbers of CD8+ cells are acquired during infection or whether persons with a low number of CD8+ cells in the nose might have a higher risk of acquiring leprosy.

Ultrastructural observations of small blood vessels in leprosy patients.

In lepromatous leprosy, blood vessels revealed the luminal protrusions of endothelial cells containing M. leprae and thickening of the basement membrane of endothelial and smooth cells. Endothelial projections with increased pinocytotic vesicles were more often encountered in lepromatous leprosy than in the other types of leprosy. On the other hand, in tuberculoid leprosy, the extensive rough endoplasmic reticulum suggesting protein synthesis was observed in the endothelial cells compared with the other types of leprosy and non-specific lesions. It seems that the blood vessels associated with hyperfunction and proliferation in the endothelium could aggravate the degenerative changes in peripheral nerve fibers including the Schwann cells.