Pentoxifylline, which inhibits tumor necrosis factor-alpha (TNF alpha), decreases human immunodeficiency virus replication in peripheral blood mononuclear cells. However, TNF alpha is important in cellular defense against M. avium-intracellulare complex (MAC), a common infection in advanced AIDS. The effect of pentoxifylline on mycobacterial colony counts in macrophages with in vivo MAC infection was evaluated, and differences in lipopolysaccharide (LPS)-induced TNF release in infected and uninfected macrophages were determined. Macrophages with in vivo MAC infection released much less TNF alpha in response to LPS (P = .01). The response was partially restored after antimycobacterial therapy. Pentoxifylline, in a concentration that inhibited LPS-induced TNF alpha by 52.4%, increased MAC counts by 2.5- to 50.0-fold. Thus, macrophages from AIDS patients with disseminated MAC infection are deficient in their ability to release TNF alpha, and further inhibition by pentoxifylline may be detrimental.

Severe weight loss is a common manifestation of advanced infection with the human immunodeficiency virus. The level of tumor necrosis factor alpha (TNF-alpha), an inducer of cachexia in laboratory animals, is elevated in the serum of some patients with AIDS. In a pilot study, five patients with unexplained AIDS-related wasting were treated with pentoxifylline, a known suppressor of TNF-alpha production. Three of the five patients had elevated baseline serum levels of TNF-alpha, and these three patients did not have significant weight gain after 4-8 weeks of pentoxifylline therapy despite the reduction of serum TNF-alpha levels. The remaining two patients, who did not have elevated serum levels of TNF-alpha, continued to lose weight and developed extensive bacterial pneumonia within 3 weeks of starting pentoxifylline therapy. Thus, therapy with pentoxifylline did not clearly benefit the patients with AIDS-related wasting in this uncontrolled pilot study; indeed, it might have been harmful for a subgroup of these patients.

Pentoxifylline, a tumor necrosis factor-alpha (TNF) inhibitor, is being tested as a treatment adjunct in human immunodeficiency virus (HIV)-infected patients. However, TNF is important in cellular defense. The effect of pentoxifylline on Mycobacterium avium complex (MAC) growth in exogenously infected macrophages was compared with the effect of dexamethasone. Pentoxifylline, in a concentration that decreased MAC-induced TNF by 48.1%, enhanced MAC growth by 1.9- to 19.6-fold and 1.82- to 4.46-fold in macrophages from normal and HIV-infected patients, respectively. It also induced interleukin-6 (IL-6) in infected macrophages. IL-6 induction correlated with the increase in MAC growth (y = 0.89 + 0.266x, P = .025). Dexamethasone in an equivalent TNF-suppressing concentration also increased MAC growth but was less effective. Unlike pentoxifylline, dexamethasone suppressed IL-6 and the suppression correlated inversely with MAC growth (y = 0.248 + 9.942x, P = .003). Thus, TNF and IL-6 are important in macrophage defense against MAC. Pentoxifylline and dexamethasone should be used with caution in AIDS patients.

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