Researchers at the University of Pennsylvania have demonstrated that morphine withdrawal complicates hepatitis C by suppressing IFN-alpha-mediated immunity and enhancing virus replication. The paper by Wang et al., �Morphine withdrawal enhances hepatitis C virus (HCV) replicon expression,� appears in the November issue of The American Journal of Pathology and is accompanied by a commentary.
Hepatitis C virus (HCV) is common among intravenous drug users, with 70 to 80% of abusers infected in the United States. This high association has peaked interest in determining the effects of drug abuse, specifically opiates, on progression of the disease. The discovery of such an association would impact treatment of both HCV infection and drug abuse.
Dr. Wen-Zhe Ho has been interested in such interplay for some time. His laboratory has previously shown using cell culture that morphine enhances virus replication and inhibits IFN-alpha (a natural anti-viral factor produced by immune, as well as host cells, and the only one approved in recombinant form for treating HCV infection). To further these results, his lab has used a cell model system to determine the consequences of morphine withdrawal, which is a common recurring event in opioid users.
Chuan-Qing Wang and colleagues examined the effects of morphine withdrawal (MW) on HCV-infected cultured liver cells by exposing cells to the drug for four days followed by its removal. They also assessed the effects of using naloxone, to block the opioid receptors, in conjunction with drug removal, i.e. precipitated morphine withdrawal (PW). To measure HCV replication, they used a virus-like �replicon� that mimics the events that occur in liver cells and expression of viral RNA and proteins that HCV uses. Although the replicon does not produce the infectious virus, the HCV replicon system represents the best available system for examining the impact of opiates on HCV at the time of their research study.
Similar to their previous results, the authors found that MW and PW increased levels of HCV replicon RNA and protein expression. In addition, both withdrawal scenarios inhibited IFN-alpha expression in liver cells in the presence or absence of HCV replicon. Since IFN-alpha is a critical self-defense mechanism utilized by liver cells to fight off viral infection, including HIV, this study suggests that morphine withdrawal weakens host cell immunity and provides a favorable environment for HCV growth in the liver.
The authors extended their study by examining the mechanism behind these observations. MW and PW inactivated the IFN-alpha promoter (the switch for making IFN-alpha) by directly inhibiting its activator, interferon regulatory factor-7 (IRF-7), and this effect was more pronounced in HCV replicon-containing cells. Finally, the ability of IFN-alpha treatment to block HCV replicon expression (85%) fell following MW (60%) and PW (50%). This finding, in conjunction with the earlier report by the same group, provides an explanation to the question of why so many HCV-infected patients fail to respond to IFN-alpha treatment.
Although the clinical relevance of this study remains to be determined, these data showing that withdrawal promotes HCV expression by suppressing anti-HCV factor (IFN-alpha) production by liver cells suggests that �opioid abuse may contribute to the chronicity of HCV infection and promote HCV disease progression.� The study also underscores the necessity of future clinical and epidemiological studies to define the role of opiate abuse in promoting HCV disease.
These results suggest that opioid abusers experiencing periods of drug abuse, followed by periods of withdrawal (due to lack of supplies) may lead to immunocompromised liver. These findings further support the need for methadone maintenance treatment as an additional benefit for opioid abusers.
Research was supported by National Institute on Drug Abuse, National Institutes of Health.
This work involved collaborators at Joseph Stokes, Jr. Research Institute at The Children’s Hospital of Philadelphia; The Center for Studies of Addiction, University of Pennsylvania School of Medicine; and The Children’s Hospital of Fudan University, Shanghai, China.
Wang C-Q, Li Y, Douglas SD, Wang X, Metzger DS, Zhang T, Ho W-Z: Morphine withdrawal enhances hepatitis C virus (HCV) replicon expression. Am J Pathol 2005, 167:1333-1340
The American Journal of Pathology, the official journal of the American Society for Investigative Pathology (ASIP), seeks to publish high-quality original papers on the cellular and molecular mechanisms of disease. The editors accept manuscripts which report important findings on disease pathogenesis or basic biological mechanisms that relate to disease, without preference for a specific method of analysis. High priority is given to studies on human disease and relevant experimental models using cellular, molecular, biological, animal, chemical and immunological approaches in conjunction with morphology.
ntravenous (IV) drug users who abuse morphine, then withdraw from it later, may be unknowingly complicating the beneficial effects of their hepatitis C treatment or giving their hepatitis infection an unwanted boost. That’s the conclusion of a study by researchers at Children’s Hospital of Philadelphia, the University of Pennsylvania and in China.1 The findings are published in the November issue of the American Journal of Pathology.
Detrimental Effects of Morphine Withdrawal
Quitting morphine in this population of hepatitis C patients may suppress the benefits of interferon-alfa in the body and enhance the replication of the virus, the study investigators led by Wen-Zhe Ho, MD, a research associate professor in the division of Immunologic and Infectious Diseases at Children’s Hospital of Philadelphia, reported.
According to the study investigators, hepatitis C infection is common among IV drug users; up to 90 percent of such users are infected with HCV in the United States, and one-fifth to one-half have chronic infection.2 The high numbers of these patients with the disease has prompted medical researchers to study the effects of drug abuse, especially the use of opiates, on HCV progression.
„In the case of HCV infection, there is little information about whether drug abuse, such as heroin, enhances HCV replication and promotes HCV disease progression,“ wrote Ho and his team. „This lack of knowledge about the impact of opioid abuse on HCV disease is a major barrier to fundamental understanding of HCV-related morbidity and mortality among intravenous drug users and to the development of new therapeutic approaches for HCV infection.“
The scientists theorized that illicit drugs might be able to detrimentally alter the immune response against the viral infection in some way. Other studies, they pointed out, showed that these drugs have the ability to block the production of beneficial interferons in the body that normally fight the virus.
Morphine’s Effect on Hepatitis C Studied Previously
In a previous study, Ho and his colleagues found that morphine boosted the virus‘ growth and interfered with interferon alfa in a collection of liver cells.3 Interferon alfa is the basis for the pegylated interferon that people with hepatitis C take as medication for the disease today in combination with the antiviral oral drug, ribavirin.4 Also produced naturally in the body, interferon is an antiviral factor produced by certain cells.
The follow-up to that laboratory-based study was the latest research aimed at determining how withdrawing from morphine might affect the course of the disease. „Physical dependence on morphine is characterized by the occurrence of an abstinence or withdrawal syndrome on termination of the drug,“ wrote Ho and his fellow investigators. These abstinence syndromes also can occur during the use of an opioid antagonist such as naloxone (Narcan), a drug that reverses the effects of narcotics, the researchers explained. Thus, they also tested the effect of naloxone-induced morphine withdrawal for the study.
Ho and his team exposed a group of liver cells kept in culture to morphine for four days, then removed it. The scientists also used a model that mimicked the events that occur in liver cells when genetic material (HCV RNA) and proteins used by the hepatitis C virus to create infection are present. This allowed the researchers to mimic the replication patterns of the virus without actually using an infectious virus.
Effects of Morphine Withdrawal
Similar to what they found in their previous study,3 Ho and his colleagues learned that removing morphine boosted levels of HCV RNA (the genetic material used by the virus) and hepatitis C viral protein in the cells. This, in essence, indicates that the viral infection is spreading. However, 72 hours after morphine was removed, HCV RNA levels decreased, suggesting there was only a temporary surge.
Withdrawing the morphine also blocked interferon-alfa production in the liver cells compared to cells in which morphine was not withdrawn. Since interferon-alfa is a critical self-defense mechanism used by liver cells to fight off attacks by the hepatitis C virus or HIV, the findings suggest that drug abusers who quit using morphine can weaken their immune system’s ability to defend the body against an HCV infection, and provides a favorable environment for hepatitis C viral growth in the liver.
Underlying Causes Studied
Next, Ho’s group wanted to understand why removing morphine created such a beneficial environment for the hepatitis C virus. They learned that removing morphine from liver cells blocked the production of interferon-alfa by, in turn, suppressing its activator, interferon regulatory factor-7 (IRF-7). The team also found that the ability of interferon-alfa to block HCV replication (or the model of HCV in this case) fell by nearly two-thirds.
The same detrimental effect of morphine removal also occurred in relation to manmade interferon alfa. This manmade, or recombinant, form is similar to the interferon medication used for people with hepatitis C today. When synthetic interferon was added to the cell lines, they demonstrated a strong ability to fight off the hepatitis virus. However, when morphine was withdrawn from the cells, the anti-HCV ability of interferon-alfa „was significantly diminished,“ Ho and his colleagues wrote.
These results were observed when morphine was directly withdrawn or indirectly removed by using naloxone, they reported, and even to a greater extent in the latter case.
„Collectively, these new observations in conjunction with our earlier findings support the notion that opioid abuse is a co-factor that promotes HCV replication,“ wrote Ho and his colleagues.
The researchers point out that the clinical relevance of this study remains to be determined, but the findings suggest that „opioid abuse may contribute to the chronicity of HCV infection and promote HCV disease progression.“
They recommend both clinical and epidemiological studies be launched to better define the rule of drug abuse in the context of HCV infection. In the meantime, they say drug abusers who use such opioids as morphine, followed by periods of withdrawal due to lack of supplies, may be doing much more harm to their livers.
„Our findings provide a plausible interpretation of the high failure rate of interferon-alfa therapy in intravenous drug users,“ the investigators concluded. „The identification of mechanism(s) involved in morphine’s action on the anti-HCV effect of interferon-alfa has the potential to improve interferon-alfa-based treatment for HCV-infected IV drug users.“
In an accompanying editorial,5 Kevin Moore, PhD, and Geoff Dusheiko, MD, both professors of Hepatology at Royal Free and University College Medical School in London, write that the findings suggest that IV drug abusers or those receiving opioid substitutes like methadone, and who are infected with HCV, may have more difficulty clearing the virus.
„Until recently, there were no data on the effects of opiates on HCV replication or the development of liver injury and fibrosis, one of the earliest features of progression to cirrhosis,“ wrote Moore and Dusheiko.
„The growing implication from these and other studies is that continued opiate abuse leads to enhanced viral replication, liver injury, and … fibrosis. Further studies are required to determine whether these effects occur in humans, as well,“ they wrote.