Pentoxifylline: a drug with wide spectrum applications in dermatology.

Pentoxifylline (PTX) is a methylxanthine derivative with a variety of anti-inflammatory effects. Currently, PTX is approved by the Food and Drug Administration for the treatment of intermittent claudication, but studies have shown that it has a variety of physiological effects at the cellular level, which may be important in treating a diverse group of diseases.

Induction of apoptosis in monocytes by Mycobacterium leprae in vitro: a possible role for tumour necrosis factor-alpha.

A diverse range of infectious organisms, including mycobacteria, have been reported to induce cell death in vivo and in vitro. Although morphological features of apoptosis have been identified in leprosy lesions, it has not yet been determined whether Mycobacterium leprae modulates programmed cell death. For that purpose, peripheral blood mononuclear cells obtained from leprosy patients were stimulated with different concentrations of this pathogen. Following analysis by flow cytometry on 7AAD/CD14+ cells, it was observed that M. leprae induced apoptosis of monocyte-derived macrophages in a dose-dependent manner in both leprosy patients and healthy individuals, but still with lower efficiency as compared to M. tuberculosis. Expression of tumour necrosis factor-alpha (TNF-alpha), Bax-alpha, Bak mRNA and TNF-alpha protein was also detected in these cultures; in addition, an enhancement in the rate of apoptotic cells (and of TNF-alpha release) was noted when interferon-gamma was added to the wells. On the other hand, incubation of the cells with pentoxifylline impaired mycobacterium-induced cell death, the secretion of TNF-alpha, and gene expression in vitro. In addition, diminished bacterial entry decreased both TNF-alpha levels and the death of CD14+ cells, albeit to a different extent. When investigating leprosy reactions, an enhanced rate of spontaneous apoptosis was detected as compared to the unreactive lepromatous patients. The results demonstrated that M. leprae can lead to apoptosis of macrophages through a mechanism that could be at least partially related to the expression of pro-apoptotic members of the Bcl-2 protein family and of TNF-alpha. Moreover, while phagocytosis may be necessary, it seems not to be crucial to the induction of cell death by the mycobacteria.

Induction of apoptosis in monocytes by Mycobacterium leprae in vitro: a possible role for tumour necrosis factor-alpha

A diverse range of infectious organisms, including mycobacteria, have been reported to induce cell death in vivo and in vitro. Although morphological features of apoptosis have been identified in leprosy lesions, it has not yet been determined whether Mycobacterium leprae modulates programmed cell death. For that purpose, peripheral blood mononuclear cells obtained from leprosy patients were stimulated with different concentrations of this pathogen. Following analysis by flow cytometry on 7AAD/CD14+ cells, it was observed that M. leprae induced apoptosis of monocyte-derived macrophages in a dose-dependent manner in both leprosy patients and healthy individuals, but still with lower efficiency as compared to M. tuberculosis. Expression of tumour necrosis factor-alpha (TNF-alpha), Bax-alpha, Bak mRNA and TNF-alpha protein was also detected in these cultures; in addition, an enhancement in the rate of apoptotic cells (and of TNF-alpha release) was noted when interferon-gamma was added to the wells. On the other hand, incubation of the cells with pentoxifylline impaired mycobacterium-induced cell death, the secretion of TNF-alpha, and gene expression in vitro. In addition, diminished bacterial entry decreased both TNF-alpha levels and the death of CD14+ cells, albeit to a different extent. When investigating leprosy reactions, an enhanced rate of spontaneous apoptosis was detected as compared to the unreactive lepromatous patients. The results demonstrated that M. leprae can lead to apoptosis of macrophages through a mechanism that could be at least partially related to the expression of pro-apoptotic members of the Bcl-2 protein family and of TNF-alpha. Moreover, while phagocytosis may be necessary, it seems not to be crucial to the induction of cell death by the mycobacteria.

Does pentoxifylline find a place in the armementarium of leprologists in type II reaction?

Alternative therapeutic interventions in Type II lepra reaction are being considered following serious problems associated with the use of steroids and thalidomide. Pentoxifylline (PTX) has been used in Type II reaction with varying degrees of success. The results of a study on the use of this drug in a dose of 1200 mg per day for a period of 2 months in patients with ENL reaction are discussed. Five patients, one of whom was HIV positive--all with severe Type II reaction, were regularly evaluated for regression of inflammatory symptoms and clinical involution of ENL lesions while on PTX therapy and thereafter. It was found that PTX led to a total elimination of systemic symptoms within a week. ENL lesions regressed in two weeks. However, in one patient, lesions recurred after one month of therapy. It appears that PTX is well tolerated and could be used as an additional drug in the armamentarium of leprologists in the management of Type II reaction, especially in HIV co-infection, where long-term steroids are contraindicated. However, further studies to compare the effects of PTX with currently, widely used drugs for the treatment of ENL reaction are necessary.

Pentoxifylline downregulates nitric oxide and tumor necrosis factor-alpha induced by mycobacterial lipoarabinomannan in a macrophage cell line.

Pentoxifylline (PTX), a phosphodiesterase inhibitor, is known to downregulate tumor necrosis factor-alpha (TNF-alpha) secretion induced by lipopolysacchride (LPS) and gamma interferon (IFN-gamma). We have had limited success in treating leprosy reactions, including erythema nodosum leprosum (ENL), in which TNF-alpha has been identified as a major proinflammatory cytokine. PTX inhibited production of NO (IC50 approximately equal to 1.0 mg/ml) and TNF-alpha (IC50 approximately equal to 0.05 mg/ml) in a dose-dependent fashion. As little as 0.5 mg/ml of PTX decreased NO production and 0.01 mg/ml of PTX inhibited TNF-alpha production. Western blot analyses demonstrated that iNOS was suppressed by PTX. Northern blot analyses showed significant reduction of TNF-alpha mRNA. We conclude that PTX is an effective inhibitor of lipoarabinomannan (LAM)-induced TNF-alpha production at both the product and transcriptional levels in our macrophage cell line. PTX also showed moderate inhibition of NO at the product level as well as translation of iNOS.

Sequential analysis of erythrocyte aggregation in health and diseases.

Aggregation of erythrocytes requires prolonged interaction of cellular and plasma constituents similar to in vivo conditions. To achieve this and then to analyse this process in various clinical and laboratory conditions, a PC-AT based system is developed. The erythrocyte suspension at 5% hematocrit in plasma is placed in a glass chamber, and the changes in laser transmitted intensity due to movement of the aggregates and erythrocytes in the path of the beam are sequentially recorded. From these data, aggregate size index, aggregate sedimentation time index, time required for completion of process and total number of fluctuations are calculated. From these, two additional parameters - effective number of cells and effective sedimentation duration - are calculated. The results show that in leprosy the aggregation of erythrocytes is reduced. In in vitro studies due to the cholesterol-enrichment of the erythrocyte membrane and treatment with pentoxifylline the aggregation of cells is increased whereas in disprin treated cells this is reduced compared to that of normal erythrocytes.