Browsing by Subject "Cocaine -- Immunology"
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Item Alteration of immune responses by cocaine: Cytokines and reactive nitrogen intermediates(Texas Tech University, 1998-08) Starnes, Joel D,In recent years cocaine abuse has reached epidemic proportions. The use of cocaine, like many other drugs of abuse, has been shown to have immunomodulatory consequences. However, the effects of cocaine on the immune system have not been thoroughly examined. The macrophage (M0) plays a central role in the regulation of inflammatory responses, antigen presentation, and is an important non-specific first line of defense against incoming pathogens. In the present studies, the immunomodulatory effects of cocaine on certain aspects of M0 functions were examined. Cocaine was administered to experimental mice and/or M0 were exposed to cocaine or one of its metabolites in vitro. Experiments were conducted to determine the effects of cocaine on the ability of M0 to produce cytokines and reactive nitrogen intermediates (RNI). A novel method of cytokine induction using a mannose receptor ligand was also developed. Mannosylated bovine serum albumin (M-BS A) was administered to a variety of cell types including M0, and shown to induce cytokine secretion. M0 from cocaine-injected mice displayed a reduced ability to secrete proinflammatory cytokines when stimulated with M-BSA. This effect was also demonstrated by M0 exposed to cocaine in vitro. However, due to the acute nature of cocaine's effects, it had no effect on the secretion of regulatory cytokines. Cytokine mRNA levels were unaffected by cocaine exposure, suggesting the mechanism of inhibition involved attenuation of cytokine secretion, but not transcription. In vivo cocaine administration, but not in vitro cocaine exposure, caused inhibition of RNI in M0. In vitro exposure to the metabolite norcocaine inhibited nitrite production, suggesting a possible in vivo mechanism. iNOS levels were analyzed via Western blot, showing that iNOS protein levels were unaffected by norcocaine. The mechanism of inhibition appeared to be through the attenuation of iNOS enzymatic activity. Collectively, these studies indicate that cocaine impairs M0 proinflammatory activity and has the ability to cause immune system compromise. These studies suggest that the immunoregulatory effects of cocaine may lead to increased instances of infectious disease in drug addict populations.Item Inhibition of virus replication by cocaine: alterations in interferon production and calcium regulation(Texas Tech University, 1999-12) Grattendick, Kenneth JohnPrevious studies have demonstrated cocaine to have a myriad of effects on the immune system. Depending on which component of the immune system is studied and the methods used, cocaine has been shown to possess both stimulatory and inhibitory effects. Cocaine has also been associated with an increase in the risk of developing infectious diseases, although a direct correlation has yet to be determined. The studies presented in this dissertation describe the effects of cocaine on host resistance to viral infections. Cocaine was found to possess antiviral properties in macrophages (Mø). L929 cells, and Madin Darby canine kidney (MDCK) cells in vitro. This effect was dose-dependent in all of these cells with 100 µg/ml exhibiting the maximal inhibition. A similar dose-dependent inhibition was observed in M0 exposed to norcocaine, a metabolite of cocaine. However, other metabolites did not show any effects on virus replication. Cocaine induced a time-dependent increase in the antiviral activity of Mǿ that was not reproduced in L929 or MDCK cells. On average, the antiviral effect of cocaine required approximately 24—48 hr to appear, indicating that the effect was not due to a direct interaction of cocaine and virus. Cocaine's inhibition of virus replication could be reversed by the addition of either antibodies to interferons (IFN) or calcium ionophores. An indication that the effect of cocaine was due to the secretion of an antiviral protein was found in experiments showing that the antiviral effect could be transferred from cells incubated with cocaine to unstimulated cells. This antiviral product was found to accumulate over time in the media and could be neutralized by the addition of anti-IFN. In studies to determine the direct effects of cocaine on IFN production, cocaine was found to induce a 2-3-fold increase in IFN secretion in both L929 cells and M0, with similar increases in IFN transcripts. Cocaine also demonstrated the ability to inhibit cell proliferation, an effect attributed to the production of IFN. Experiments were also conducted to determine if the antiviral effects of cocaine observed in vitro could be demonstrated in an animal model. C57B1/6 mice were infected with Influenzavirus A and given daily i.p. injections of 10 mg/kg cocaine or saline. Cocaine-injected mice were visibly less sick than control animals and had 50% less virus in their lungs, as determined by hemagglutination. This reduction in virus load was consistent with the previous in vitro experiments with cocaine. Because the addition of calcium ionophores had been demonstrated to reverse the antiviral effect of/« vitro cocaine exposure, studies were conducted to determine the effects of cocaine on intracellular calcium (Ca^2+) regulation. Mø incubated with 100 µg/ml cocaine for 48-72 hr demonstrated a 41% increase in steady-state Ca^2+ concentrations. This effect was observed when cells were assayed either in the presence or absence of extracellular Ca^2+ indicating an alteration in calcium regulation that was localized to either the cytoplasm or intracellular membranes. Studies on the mobilization of Ca^2+ showed an increase m ATP-induced Ca^2+ transients when Mø were incubated with cocaine. Calcium ATPase inhibitors reduced the calcium increases in cocaine-treated Mø, further supporting the hypothesis that cocaine was increasing calcium mobilization. This result also indicated that the mechanism by which cocaine altered intracellular Ca levels was most likely localized to the endoplasmic reticulum Ca^2+ -ATPases. In summary, cocaine was found to inhibit virus replication by increasing IFN production and altering cytoplasmic Ca^2+ levels.