Recent studies have revealed a positive correlation between astrocyte apoptosis and rapid disease progression in persons with neurodegenerative diseases. Glycogen synthase kinase 3β (GSK-3β) is a molecular regulator of cell fate in the central nervous system and a target of the phosphatidylinositol 3-kinase (PI-3K) pathway. We have therefore examined the role of the PI-3K pathway, and of GSK-3β, in regulating astrocyte survival. Our studies indicate that inhibition of PI-3K leads to apoptosis in primary cortical astrocytes. Furthermore, overexpression of a constitutively active GSK-3β mutant (S9A) is sufficient to cause astrocyte apoptosis, whereas an enzymatically inactive GSK-3β mutant (K85M) has no effect. In light of reports on the interplay between GSK-3β and nuclear factor κB (NF-κB), and because of the antiapoptotic activity of NF-κB, we examined the effect of GSK-3β overexpression on NF-κB activation. These experiments revealed strong inhibition of NF-κB activation in astrocytes upon overexpression of the S9A, but not the K85M, mutant of GSK-3β. This was accompanied by stabilization of the NF-κB-inhibitory protein, IκBα and down-regulation of IκB kinase (IKK) activity. These findings therefore implicate GSK-3β as a regulator of NF-κB activation in astrocytes and suggest that the pro-apoptotic effects of GSK-3β may be mediated at least in part through the inhibition of NF-κB pathway.

Background: Unlike CD4+ T cells, HIV-1 infected macrophages exhibit extended life span even upon stress, consistent with their in vivo role as long-lived HIV-1 reservoirs. Results: Here, we demonstrate that PI3K/Akt inhibitors, including clinically available Miltefosine, dramatically reduced HIV-1 production from long-living virus-infected macrophages. These PI3K/Akt inhibitors hyper-sensitize infected macrophages to extracellular stresses that they are normally exposed to, and eventually lead to cell death of infected macrophages without harming uninfected cells. Based on the data from these Akt inhibitors, we were able to further investigate how HIV-1 infection utilizes the PI3K/Akt pathway to establish the cytoprotective effect of HIV-1 infection, which extends the lifespan of infected macrophages, a key viral reservoir. First, we found that HIV-1 infection activates the well characterized pro-survival PI3K/Akt pathway in primary human macrophages, as reflected by decreased PTEN protein expression and increased Akt kinase activity. Interestingly, the expression of HIV-1 or SIV Tat is sufficient to mediate this cytoprotective effect, which is dependent on the basic domain of Tat – a region that has previously been shown to bind p53. Next, we observed that this interaction appears to contribute to the downregulation of PTEN expression, since HIV-1 Tat was found to compete with PTEN for p53 binding; this is known to result in p53 destabilization, with a consequent reduction in PTEN protein production. Conclusion: Since HIV-1 infected macrophages display highly elevated Akt activity, our results collectively show that PI3K/Akt inhibitors may be a novel therapy for interfering with the establishment of long-living HIV-1 infected reservoirs.

Despite the use of anti-retroviral therapies, a majority of HIV-infected individuals still develop HIV-Associated Neurocognitive Disorders (HAND), indicating that host inflammatory mediators, in addition to viral proteins, may be contributing to these disorders. Consistently, we have previously shown that levels of the inflammatory mediator soluble CD40L (sCD40L) are elevated in the circulation of HIV-infected, cognitively impaired individuals as compared to their infected, non-impaired counterparts. Recent studies from our group suggest a role for the CD40/CD40L dyad in blood brain barrier (BBB) permeability and interestingly, sCD40L is thought to regulate BBB permeability in other inflammatory disorders of the CNS. Using complementary multiphoton microscopy and quantitative analyses in wild-type and CD40L deficient mice, we now reveal that the HIV transactivator of transcription (Tat) can induce BBB permeability in a CD40L-dependent manner. This permeability of the BBB was found to be the result of aberrant platelet activation induced by Tat, since depletion of platelets prior to treatment reversed Tat-induced BBB permeability. Furthermore, Tat treatment led to an increase in granulocyte antigen 1 (Gr1) positive monocytes, indicating an expansion of the inflammatory subset of cells in these mice, which were found to adhere more readily to the brain microvasculature in Tat treated animals. Exploring the mechanisms by which the BBB becomes compromised during HIV infection has the potential to reveal novel therapeutic targets, thereby aiding in the development of adjunct therapies for the management of HAND, which are currently lacking.

HIV-1–associated neuroinflammation persists even with effective combined antiretroviral therapy, and it is associated with the presence of activated monocytes/macrophages within the CNS. To infiltrate the CNS, monocytes transmigrate across the selectively permeable blood–brain barrier, which is compromised during HIV-1 infection. Interestingly, platelet-derived excess soluble CD40 ligand found in the plasma and cerebrospinal fluid of HIV-1–infected individuals with cognitive impairment has previously been implicated in increased blood–brain barrier permeability. In this study we show that soluble CD40 ligand also promotes the formation of complexes between inflammatory monocytes and activated platelets (PMCs), which are detected by flow cytometry as monocytes that express excess of CD61, a platelet marker, and that these complexes are increased in individuals with HIV-1 infection. PMCs exhibit an enhanced ability to adhere to human brain microvascular endothelial cells as compared with monocytes alone, and they migrate across the transendothelial barrier. These complexes can be found marginalized in the lumen of postcapillary venules in postmortem brain tissue derived from cases of HIV-1–associated encephalitis. The extravasation of monocytes across the brain endothelium may exacerbate neuroinflammation, indicating that enhancing this event via platelet interaction may be a contributing factor in the development of cognitive impairment. Thus, dampening platelet activation, and in turn PMC formation, with antiplatelet agents may prove beneficial in developing adjunctive therapies for use in combination with combined antiretroviral therapy in an effort to reduce HIV-1–associated neurologic deficit.

Cannabis continues to be the most used drug in the world today. Research shows that cannabis use is associated with a wide range of adverse health consequences that may involve almost every physiological and biochemical system including respiratory/pulmonary complications such as chronic cough and emphysema, impairment of immune function, and increased risk of acquiring or transmitting viral infections such as HIV, HCV, and others. The review of published research shows that cannabis use may impair immune function in many instances and thereby exerts an impact on viral infections including human immune deficiency virus (HIV), hepatitis C infection (HCV), and human T-cell lymphotropic type I and II virus (HTLV-I/II). The need for more research is also highlighted in the areas of long-term effects of cannabis use on pulmonary/respiratory diseases, immune dysfunction and the risk of infection transmission, and the molecular/genetic basis of immune dysfunction in chronic cannabis users.