Inhibitory effect of the immunosuppressant FK506 on apoptotic cell death induced by HIV-1 gp120

Cardiovascular disease in HIV infection

The survival of patients with HIV infection who have access to highly active antiretroviral therapy has dramatically increased. In HIV-infected persons, cardiovascular disease can be associated with HIV infection, opportunistic infections or neoplasias, use of antiretroviral drugs or treatment of opportunistic complications, mode of HIV acquisition (such as intravenous drug use), or with the classic non-HIV-related cardiovascular risk factors (such as smoking or age). Diseases of the heart associated with HIV infection or its opportunistic complications include pericarditis and myocarditis. Pericarditis may lead to pericardial effusion rarely causing tamponade. Cardiomyopathy is often clinically silent with asymptomatic left ventricular systolic dysfunction. Endocarditis is mainly the consequence of intravenous drug abuse, possibly leading to life-threatening valvular insufficiency with the need for cardiac surgery. A further serious condition associated with HIV infection is pulmonary hypertension potentially leading to right heart failure. The cardiovascular complications of HIV infection such as cardiomyopathy and pericarditis have been reduced by highly active antiretroviral therapy, but premature coronary atherosclerosis is now a growing problem because antiretroviral drugs can lead to serious metabolic disturbances resembling those in the metabolic syndrome. Lipodystrophy, a clinical syndrome of peripheral fat wasting, central adiposity, dyslipidemia, and insulin resistance, is most prevalent among patients treated with protease inhibitors. These patients should thus be screened for hyperlipidemia, hyperglycemia, and hypertension, and they may be candidates for lipid-lowering therapies. When initiating lipid-lowering therapy, interactions between statins and HIV protease inhibitors affecting cytochrome P450 function must be considered. Restenosis rate after percutaneous coronary intervention may be unexpectedly high.

Relationship between CD4(+)/CD8(+) T cell ratio and T cell activation in multiple myeloma: reference to IL-16

We found that the ratio of CD4(+) to CD8(+) T cells (CD4/CD8 ratio) was decreased in patients with multiple myeloma (MM) and that this decrease was significantly related to an increase of human leukocyte antigen (HLA)-DR expression by CD8(+) (but not CD4(+)) T cells (P<0.005). In addition, the serum level of interleukin (IL)-16 was significantly higher in stage III MM patients than in healthy controls (P<0.001). The decrease of CD4(+) T cells in MM may be mediated by activation of CD8(+) T cells derived cytokine IL-16. In addition, these T cell phenotypic changes and the IL-16 level appear to be useful indicators of disease activity.

Lessons from similarities between SLE and HIV infection

OBJECTIVE

We attempted to obtain deeper understanding of systemic lupus erythematosus (SLE) and human immunodeficiency virus (HIV) infection through comparative studies between both diseases.

METHOD

For this purpose, we reviewed and discussed lessons from similarities in both diseases based on our own and reported findings in literatures.

RESULT

Such comparative studies may contribute to the progress in understanding the clinical or pathogenetic features of these diseases.

CONCLUSION

Further studies into the relationship between SLE and HIV infection may bring to light important clues to assist in the development of better treatments for each disease.

A possible pathogenic role of CD8+ T cells and their derived cytokine, IL-16, in SLE

Current investigations into the role of CD8+ T cells and their derived cytokine, interleukin (IL)-16, in the induction of CD4+ T cell abnormalities in systemic lupus erythematosus (SLE) were reviewed and discussed on the basis of results mainly obtained in our laboratory.

Neuroimmunophilin ligands: evaluation of their therapeutic potential for the treatment of neurological disorders

Neuroimmunophilin ligands are a class of compounds that hold great promise for the treatment of nerve injuries and neurological disease. In contrast to neurotrophins (e.g., nerve growth factor), these compounds readily cross the blood-brain barrier, being orally effective in a variety of animal models of ischaemia, traumatic nerve injury and human neurodegenerative disorders. A further distinction is that neuroimmunophilin ligands act via unique receptors that are unrelated to the classical neurotrophic receptors (e.g., trk), making it unlikely that clinical trials will encounter the same difficulties found with the neurotrophins. Another advantage is that two neuroimmunophilin ligands (cyclosporin A and FK-506) have already been used in humans (as immunosuppressant drugs). Whereas both cyclosporin A and FK-506 demonstrate neuroprotective actions, only FK-506 and its derivatives have been clearly shown to exhibit significant neuroregenerative activity. Accordingly, the neuroprotective and neuroregenerative properties seem to arise via different mechanisms. Furthermore, the neuroregenerative property does not involve calcineurin inhibition (essential for immunosuppression). This is important since most of the limiting side effects produced by these drugs arise via calcineurin inhibition. A major breakthrough for the development of this class of compounds for the treatment of human neurological disorders was the ability to separate the neuroregenerative property of FK-506 from its immunosuppressant action via the development of non-immunosuppressant (non-calcineurin inhibiting) derivatives. Further studies revealed that different receptor subtypes, or FK-506-binding proteins (FKBPs), mediate immunosuppression and nerve regeneration (FKBP-12 and FKBP-52, respectively, the latter being a component of steroid receptor complexes). Thus, steroid receptor chaperone proteins represent novel targets for future drug development of novel classes of compounds for the treatment of a variety of human neurological disorders, including traumatic injury (e.g., peripheral nerve and spinal cord), chemical exposure (e.g., vinca alkaloids, Taxol) and neurodegenerative disease (e.g. , diabetic neuropathy and Parkinson's disease).

Relationship between CD4+/CD8+ T cell ratio and T cell activation in systemic lupus erythematosus

We investigated the relationship between the ratio of CD4+ to CD8+ T cells (CD4/CD8 ratio) and T cell activation, indicated by human leukocyte antigen (HLA)-DR expression, in patients with systemic lupus erythematosus (SLE). We found that the ratio was decreased in SLE patients and that this was significantly related to expression of HLA-DR by CD8+ (but not CD4+) T cells. These findings may assist in understanding the pathogenesis of SLE. In some SLE patients, the CD4/CD8 ratio and HLA-DR expression may be good indicators of therapeutic efficacy.

Immunoaugmenting effect of FK 506 on experimental allergic encephalomyelitis in Lewis rats

The effect of the immunosuppressive drug FK 506 on encephalomyelitis (EAE) in Lewis rats was studied. Treatment that began during EAE induction delayed EAE onset, but when the disease started it was chronic/progressive and of unusual severity and duration, leading to death in many animals. Treatment started after onset of EAE shortened the disease. Forty seven days after immunization, extensive demyelination and inflammation were observed in the spinal cords of rats treated with FK 506 from the day of EAE induction. Rats treated after EAE onset had only minimal pathological abnormalities.

Calmodulin antagonists inhibit apoptosis of CD4+ T-cells from patients with AIDS

Recent studies indicate that Fas and Fas ligand are involved in apoptosis of T-cells in HIV-infected patients. We have demonstrated that calcium/calmodulin is involved in Fas-mediated apoptosis in human T-cell lines transfected with HIV recombinant cDNA. In the present study, we examined spontaneous apoptosis of T-cells in vitro in peripheral blood obtained from 11 patients with AIDS and 8 HIV-seronegative normal donors and the effect of the calmodulin antagonists, trifluoperazine (TFP) or tamoxifen (TMX), on apoptosis. The results show that: (1) levels of spontaneous apoptosis were higher in PBMCs obtained from patients with AIDS than HIV-negative normal controls and the levels of apoptosis correlated with the severity of disease. (2) The accelerated apoptosis occurred predominantly in CD4+ cells in patients with AIDS. (3) Calmodulin antagonists inhibited the spontaneous apoptosis of CD4+ T-cells from patients with AIDS, which resulted in an increase in the ratio of CD4+ to CD8+ T-cells. (4) The inhibitory effect of calmodulin antagonists on apoptosis was more significant in patients with advanced disease (CDC category C) compared to less severe disease (CDC category B). These results indicate that calmodulin antagonists inhibit HIV-associated apoptosis of CD4+ T-cells, and imply that the calcium/calmodulin play important roles in mediating apoptosis of CD4+ T-cells induced by HIV infection.

Transcriptional regulation of the human FasL promoter-enhancer region

The human FasL enhancer region was cloned and functionally characterized in transformed and primary T cells. Within the 2.3 kilobase pairs of the FasL untranslated region, the distal 3' 300-base pair portion contains a single transcription initiation site and confers basal and inducible transcriptional activity. Stimuli that increase [Ca2+]i such as CD3 cross-linking or ionomycin, but not activation of protein kinase C, were found to induce FasL enhancer transcription in a cyclosporin-sensitive manner. Moreover, calcineurin and NFAT, but not AP1, were identified as necessary and sufficient effectors in driving FasL transcription through an NFAT cis-acting motif (GGAAA). Additional modes of T cell activation such as CD4 cross-linking were also found to induce NFAT binding to the FasL enhancer region and to functionally transactivate its transcription. These results indicate that the induction of FasL gene transcription in T cells after CD3 or CD4 activation is selectively mediated by calcineurin and NFAT.

Characterization of the cytotoxic factor(s) released from thymic dendritic cells upon human immunodeficiency virus type 1 infection

We previously demonstrated that infection of primary human thymic dendritic cells (DCs) with laboratory strains of HIV leads to the release of soluble factor(s) which induced thymocyte killing. In the present paper, we extend the characterization of this process. Our results reveal that primary HIV-1 isolates are similarly able to induce the production of cytotoxic factor(s) from thymic DCs and that the release of such factor(s) is dependent on viral infection. Interestingly, we observed that CD4+ and CD8+ purified thymocyte subsets, and activated PBMCs are susceptible to the cytotoxic activity, whereas freshly isolated resting PBMCs are resistant to this effect. Cycloheximide treatment prevents the killing of thymocytes exposed to HIV-infected DC supernatant, revealing that this form of cell death is an active biological process requiring protein synthesis. Finally, our data suggest that FasL and TNF alpha could both participate in the killing process. These in vitro observations provide a plausible model, whereby HIV-infected DCs can play a role in vivo in the induction of uninfected thymocyte killing.

Circulating immune complexes from HIV-1+ patients induces apoptosis on normal lymphocytes

Isolated immune complexes from sera of 49 out of 67 human immunodeficiency virus-1-positive (HIV-1+) patients (CIC-HIV+), composed of anti-HIV-HIV-Ag, could induce apoptosis on normal phytohaemagglutinin (PHA)-activated lymphocytes. DNA degradation was detected by propidium iodide staining. This activity is directed against CD4+ lymphocytes as demonstrated by double binding of CIC-HIV+ and anti-CD4 on apoptosis cells. Expression of Fas antigen is prior to apoptotic phenomena. CIC-HIV+ apoptosis inducers belong mainly to asymptomatic HIV-infected patients, indicating that immune complexes from these patients can destroy CD4+ lymphocytes.

Human immunodeficiency virus type 2 envelope glycoprotein binds to CD8 as well as to CD4 molecules on human T cells

We report here that human immunodeficiency virus type 2 (HIV-2) envelope glycoprotein (gp105), but not HIV-1 gp120, can bind to CD8 molecules as well as to CD4 molecules on human T cells. This phenomenon may lead to differences in the life cycles of HIV-1 and HIV-2, and it may be related to the differences in disease manifestations of HIV-1 and HIV-2 infection, including longer survival of HIV-2-infected patients.

Role of curdlan sulfate in the binding of HIV-1 gp120 to CD4 molecules and the production of gp120-mediated TNF-alpha

To clarify the mechanism by which curdlan sulfate (CRDS) inhibits human immunodeficiency virus (HIV)-1 infection, we examined its influence on the binding of gp120 to CD4 molecules on T cells and macrophages, as well as on the production of TNF-alpha by gp120-stimulated macrophages (which promotes HIV-1 replication). CRDS treatment of cells not only inhibited the binding of HIV-1 gp120 to CD4+ cells, but also inhibited TNF-alpha production induced by gp120. Inhibition of HIV-1 infection by CRDS may be related to these two actions.