Focus on the heart: alcohol consumption, HIV infection, and cardiovascular disease

With the advent of effective antiretroviral therapy, people infected with HIV have a longer life expectancy and, consequently, are likely to develop other chronic conditions also found in noninfected people, including cardiovascular disease (CVD). Alcohol consumption, which is common among HIV-infected people, may influence the risk of CVD. In noninfected adults, moderate alcohol consumption can reduce the risk of coronary heart disease (CHD), heart attacks, and the most common type of stroke, whereas heavy drinking increases the risk of these cardiovascular events. These relationships can be partially explained by alcohol's effects on various risk factors for CVD, including cholesterol and other lipid levels, diabetes, or blood pressure. In HIV-infected people, both the infection itself and its treatment using combination antiretroviral therapy may contribute to an increased risk of CVD by altering blood lipid levels, inducing inflammation, and impacting blood-clotting processes, all of which can enhance CVD risk. Coinfection with the hepatitis C virus also may exacerbate CVD risk. Excessive alcohol use can further enhance CVD risk in HIV-infected people through either of the mechanisms described above. In addition, excessive alcohol use (as well as HIV infection) promote microbial translocation, the leaking of bacteria or bacterial products from the intestine into the blood stream, where they can induce inflammatory and immune reactions that damage the cardiovascular system.

Focus on: Alcohol and the immune system

Alcohol abuse suppresses multiple arms of the immune response, leading to an increased risk of infections. The course and resolution of both bacterial and viral infections is severely impaired in alcohol-abusing patients, resulting in greater patient morbidity and mortality. Multiple mechanisms have been identified underlying the immunosuppressive effects of alcohol. These mechanisms involve structural host defense mechanisms in the gastrointestinal and respiratory tract as well as all of the principal components of the innate and adaptive immune systems, which are compromised both through alcohol's direct effects and through alcohol-related dysregulation of other components. Analyses of alcohol's diverse effects on various components of the immune system provide insight into the factors that lead to a greater risk of infection in the alcohol-abusing population. Some of these mechanisms are directly related to the pathology found in people with infections such as HIV/AIDS, tuberculosis, hepatitis, and pneumonia who continue to use and abuse alcohol.

Integrating HIV/AIDS and alcohol research

Many people at risk for or already infected with HIV abuse alcohol, contributing to the difficulties in preventing the spread of the infection and treating infected patients. Thus, alcohol-abusing patients may delay testing for HIV, accessing appropriate medical care, and initiating antiretroviral therapy (ART), which may hasten disease progression to full-blown AIDS. Alcohol abuse also increases the risk of HIV infection by promoting risky behaviors and counteracting efforts to minimize the risk of infection, prevent transmission of the virus to others once exposure has occurred, and reduce the risk of progression and organ or tissue injury after infection. In HIV-infected people undergoing treatment, concurrent alcohol abuse often renders treatment ineffective because patients frequently fail to adhere to the strict treatment regimens necessary to achieve control of the infection. Moreover, alcohol may interact with ART medications and exacerbate adverse effects of these medications. Future research needs to better integrate behavioral and biological research to identify strategies to prevent the spread of HIV infection in alcohol-abusing populations as well as focus on translational research to effectively implement promising approaches on a large scale.

Alcohol's effects on brain and behavior

Over the past 40 years, rigorous examination of brain function, structure, and attending factors through multidisciplinary research has helped identify the substrates of alcohol-related damage in the brain. One main area of this research has focused on the neuropsychological sequelae of alcoholism, which has resulted in the description of a pattern of sparing and impairment that provided an essential understanding of the functional deficits as well as of spared capabilities that could be useful in recovery. These studies have elucidated the component processes of memory, problem solving, and cognitive control, as well as visuospatial, and motor processes and their interactions with cognitive control processes. Another large area of research has focused on observable brain pathology, using increasingly sophisticated imaging technologies--progressing from pneumoencephalography to computed tomography, magnetic resonance imaging (MRI), diffusion tensor imaging, and functional MRI--that have enabled ever more detailed insight into brain structure and function. These advancements also have allowed analysis of the course of brain structural changes through periods of drinking, abstinence, and relapse.

Underage alcohol use: summary of developmental processes and mechanisms: ages 16-20

Late adolescence (i.e., the age-group between 16 and 20 years) is characterized by significant changes in neurological and cognitive processes, behavioral and social functioning, and relational and physical contexts as the individual moves toward adulthood. In this age-group, major role transitions affect almost every aspect of life. Moreover, brain development continues-and with it the development of cognitive functions, working memory, emotional and behavioral self-regulation, and decisionmaking. The adolescent's social and emotional development also continues to evolve, affecting interactions with parents, siblings, peers, and first romantic relationships. All of these changes impact drinking behavior during late adolescence, and, in fact, alcohol use, binge drinking, and heavy drinking are particularly prevalent in youth ages 16-20. Determining the common trajectories of drinking behavior in this age-group is important for understanding how adolescent alcohol use helps shape adult outcomes and for identifying risk and protective factors. It also is important to study the short- and long-term consequences of adolescent alcohol use and abuse, including alcohol's effects on the developing adolescent brain and accomplishment of important developmental tasks of this age.

Laser-assisted microdissection

When analyzing alcohol's effects on the brain, researchers often want to look at small clusters of cells that can be studied in isolation from the surrounding brain tissue rather than at the entire brain or larger brain areas. This implies that relatively small numbers of cells have to be retrieved from the brain and studied in culture or subjected to biochemical analyses. The challenge then becomes how to isolate small numbers of cells from a specific brain region without including unwanted cells. One approach to solving this problem is to use a technology known as laser-assisted microdissection (LMD). This article reviews some of the principles of LMD and its use in alcohol research.

Communication networks in the brain: neurons, receptors, neurotransmitters, and alcohol

Nerve cells (i.e., neurons) communicate via a combination of electrical and chemical signals. Within the neuron, electrical signals driven by charged particles allow rapid conduction from one end of the cell to the other. Communication between neurons occurs at tiny gaps called synapses, where specialized parts of the two cells (i.e., the presynaptic and postsynaptic neurons) come within nanometers of one another to allow for chemical transmission. The presynaptic neuron releases a chemical (i.e., a neurotransmitter) that is received by the postsynaptic neuron's specialized proteins called neurotransmitter receptors. The neurotransmitter molecules bind to the receptor proteins and alter postsynaptic neuronal function. Two types of neurotransmitter receptors exist-ligand-gated ion channels, which permit rapid ion flow directly across the outer cell membrane, and G-protein-coupled receptors, which set into motion chemical signaling events within the cell. Hundreds of molecules are known to act as neurotransmitters in the brain. Neuronal development and function also are affected by peptides known as neurotrophins and by steroid hormones. This article reviews the chemical nature, neuronal actions, receptor subtypes, and therapeutic roles of several transmitters, neurotrophins, and hormones. It focuses on neurotransmitters with important roles in acute and chronic alcohol effects on the brain, such as those that contribute to intoxication, tolerance, dependence, and neurotoxicity, as well as maintained alcohol drinking and addiction.

Magnetic resonance imaging approaches for studying alcoholism using mouse models

Mice are one of the most commonly used animal models of alcoholism, and extensive genetic and behavioral data related to alcohol consumption and its consequences in different strains are available. However, only recently have researchers begun to combine magnetic resonance imaging (MRI) technology with other experimental strategies to study the effects of alcohol in mice. This powerful combination enables structural and functional data of alcohol's effects on the brain of living animals to be obtained. This article reviews the challenges associated with the use of these technologies in mice and discusses the application of these advanced technologies to mouse models of alcoholism.

Translational studies of alcoholism: bridging the gap

Human studies are necessary to identify and classify the brain systems predisposing individuals to develop alcohol use disorders and those modified by alcohol, while animal models of alcoholism are essential for a mechanistic understanding of how chronic voluntary alcohol consumption becomes compulsive, how brain systems become damaged, and how damage resolves. Our current knowledge of the neuroscience of alcohol dependence has evolved from the interchange of information gathered from both human alcoholics and animal models of alcoholism. Together, studies in humans and animal models have provided support for the involvement of specific brain structures over the course of alcohol addiction, including the prefrontal cortex, basal ganglia, cerebellum, amygdala, hippocampus, and the hypothalamic-pituitary-adrenal axis.