Cocaine Inhibits Production of Murine Hepatitis Virus by Peritoneal Macrophages In Vitro

Abstract

Our previous studies have demonstrated a number of effects of cocaine on macrophage (M phi) functions. The present studies were initiated to ascertain the effects of cocaine on virus production in vitro. C57BL/6 mice were injected intraperitoneally with thioglycollate broth, and the peritoneal M phi collected 4 days later were cultured in 96-well microtiter plates as continuous monolayers. Various concentrations of cocaine were incubated with M phi for up to 5 days. Mouse hepatitis virus (MHV) was added to these cultures, which was followed by a methyl cellulose overlay. Cocaine caused a dose-dependent inhibition of viral plaques after 48 hr of incubation. The inhibitory activity was transferable to fresh cultures of M phi, inhibiting both plaque size and number. Specific polyclonal antibodies to alpha + beta-interferon but not tumor necrosis factor or transforming growth factor-beta partially reversed the inhibition of both plaque size and plaque number. It appears that MHV induced interferon in cultured M phi, an effect that was enhanced by cocaine. Since cocaine has been reported to interfere with calcium mobilization, studies were done using ionomycin, a calcium ionophore, in order to reverse possible effects on intracellular calcium that could affect virus production. The presence of ionomycin completely reversed the inhibition of virus production by cocaine. The antiviral effects of cocaine appear to be caused by modulation of intracellular calcium and, to a lesser extent, by the enhancement of interferon production.

Cocaine Causes Increased Type I Interferon Secretion by both L929 Cells and Murine Macrophages

“…In previous experiments with M, it was determined that antiviral activity could be transferred to fresh M, indicating that cocaine-treated cells secreted antiviral products (9). However, it was not determined what the identity of this secreted product was or whether it accumulated over time, which would be expected with the induction of secreted products.…”

“…Palamara et al have described an increase in Sendai virus replication in epithelial cells cultured with cocaine in vitro, possibly caused by decreasing intracellular glutathione levels and increasing the redox state of the cells (15). Recently, our lab has described an antiviral activity of cocaine on murine peritoneal M infected with mouse hepatitis virus (MHV) in vitro (9). However, the mechanism(s) involved in this activity was not previously characterized.…”

“…The Indiana strain of vesicular stomatitis virus (VSV) was a gift from Sam Baron. The viral plaque assay has been described previously (9). Briefly, after M or L929 cells were incubated with cocaine, the culture media were discarded and 50 l of virus (MHV or VSV, respectively) diluted to approximately 40 PFU in DMEM-S was added.…”

Examination of the Nitric Oxide Production-Suppressing Component in Tinospora tuberculata.

“…Cell Culture and Assay According to the method of Lefkowitz et al, 6) mice were injected intraperitoneally with 1.5 ml of a 4% thioglycollate broth. After 4 d, the animals were sacrificed by cervical dislocation.…”

“…Peritoneal lavage was performed using cold RPMI 1640 medium. Peritoneal macrophages were centrifuged at 1000ϫg for 2 min, and the sedimented cells were resuspended at a density of 1ϫ10 6 /ml in 5% fetal calf serum (FCS)-supplemented RPMI 1640 medium. The cell suspension was added to each well of a 6-well or 96-well tissue culture plate.…”