Matrix metalloproteinases, their production by monocytes and macrophages and their potential role in HIV-related diseases

Interactions of HIV and methamphetamine: cellular and molecular mechanisms of toxicity potentiation

Methamphetamine (METH) is a highly addictive psychostimulant drug, whose abuse has reached epidemic proportions worldwide. METH use is disproportionally represented among populations at high risks for developing HIV infection or who are already infected with the virus. Psychostimulant abuse has been reported to exacerbate the cognitive deficits and neurodegenerative abnormalities observed in HIV-positive patients. Thus, the purpose of the present paper is to review the clinical and basic observations that METH potentiates the adverse effects of HIV infection. An additional purpose is to provide a synthesis of the cellular and molecular mechanisms that might be responsible for the increased toxicity observed in co-morbid patients. The reviewed data indicate that METH and HIV proteins, including gp120, gp41, Tat, Vpr and Nef, converge on various caspase-dependent death pathways to cause neuronal apoptosis. The role of reactive microgliosis in METH- and in HIV-induced toxicity is also discussed.

Activation of human monocytes after infection by human coronavirus 229E

Human coronaviruses (HCoV) are recognized respiratory pathogens that may be involved in other pathologies such as central nervous system (CNS) diseases. To investigate whether leukocytes could participate in respiratory pathologies and serve as vector for viral spread towards other tissues, the susceptibility of human leukocytic cell lines and peripheral blood mononuclear cells (PBMC) to HCoV-229E and HCoV-OC43 infection was investigated. Human primary monocytes/macrophages were susceptible to HCoV-229E infection, but strongly restricted HCoV-OC43 replication. Moreover, productive HCoV-229E infection of primary monocytes and of the THP-1 monocytic cell line led to their activation, as indicated by the production of pro-inflammatory mediators, including TNF-alpha, CCL5, CXCL10 and CXCL11 and MMP-9. Moreover, an in vitro chemotaxis assay showed that motility towards chemokines of THP-1 cells and primary monocytes was increased following an acute or persistent HCoV-229E infection. Taken together, these results suggest that infected monocytes could serve as a reservoir for HCoV-229E, become activated, participate in the exacerbation of pulmonary pathologies, as well as serve as potential vectors for viral dissemination to host tissues, where it could be associated with other pathologies.

Matrix metalloproteinase dysregulation in HIV infection: implications for therapeutic strategies

The emerging role of immune activation and inflammation in the pathogenesis of human immunodeficiency virus (HIV) disease has stimulated the search for new approaches for managing HIV infection. Recent evidence suggests that an imbalance between matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of MMPs (TIMPs) might contribute to HIV-associated pathology by inducing remodelling of the extracellular matrix. Here, we discuss the evidence and the potential mechanisms for altered MMP or TIMP function in HIV infection and disease. Furthermore, we outline the possible medical implications for the use of compounds that target MMP activity, and we propose that antiretroviral drugs, particularly HIV protease inhibitors (PIs), and compounds with anti-inflammatory properties, such as statins, natural omega-3 fatty acids and tetracyclines, which inhibit MMP function, might represent useful therapeutic approaches to mitigate potential MMP-related damage during HIV infection.

Comparison of MMP-2 and MMP-9 secretion from T helper 0, 1 and 2 lymphocytes alone and in coculture with macrophages

Metalloproteinases (MMPs) participate in extracellular matrix remodelling and regulatory signalling during chronic inflammatory states such as atherosclerosis formation. However, the sources and mediators of MMP upregulation need clarification. We investigated whether proinflammatory mouse T helper type 1 (Th1) lymphocytes are more active in MMP secretion than naïve Th0 or anti-inflammatory Th2 phenotypes, in the absence of specific antigenic stimulation, under baseline conditions and after contact with irradiated macrophages. We also compared the effect of Th0, Th1 or Th2 lymphocyte-conditioned medium and irradiated lymphocytes on MMP production from macrophages. Finally, we investigated whether CD40-CD40 ligand (CD40L) interactions were involved in T-cell-stimulated MMP secretion from macrophages. Under baseline conditions, MMP-2 messenger RNA (mRNA) and protein levels were greater in Th1 than Th0 or Th2 lymphocytes; MMP-9 mRNA, but not protein, was also upregulated. In the presence of irradiated macrophages MMP-2 and MMP-9 production from Th1 and Th2 was greater than from Th0 lymphocytes. Conditioned media from Th1 but not Th0 or Th2 cells increased MMP-9 secretion from macrophages. Irradiated Th1 lymphocytes stimulated both MMP-2 and MMP-9 secretion from macrophages more than irradiated Th2 or Th0 cells; this activation was independent of CD40-CD40L interaction. These findings demonstrate for the first time greater MMP secretion by Th1 than Th2 or Th0 lymphocytes and their greater ability to upregulate macrophage MMP secretion in the absence of specific antigenic stimulation. These mechanisms could promote matrix turnover in inflammatory states and, for example, promote atherosclerotic plaque rupture.

PGE2-induced metalloproteinase-9 is essential for dendritic cell migration

Following antigen acquisition and maturation, dendritic cells (DCs) disengage from the extracellular matrix, cross basement membranes, and travel to draining lymph nodes to activate T cells. CCR7 expression is necessary but not sufficient for the directional migration of DCs. Prostaglandin E2 (PGE2), present in inflammatory sites, induces DC migration, presumably by enacting a migration-permissive gene expression program. Since regulation of DC migration is highly important for their use in vaccination and therapy, we examined the PGE2-induced changes in the expression of metalloproteinases (MMPs). Our results indicate that PGE2 significantly up-regulates MMP-9 expression, induces both secreted and membrane-bound MMP-9, and that in turn, DC-derived MMP-9 is essential for DC chemotaxis in response to the CCR7 ligand CCL19, Matrigel migration, and in vivo migration in both wild-type and MMP-9-deficient hosts. We conclude that DCs matured within inflammatory sites require both CCR7 and PGE2-induced MMP-9 for their directional migration to draining lymph nodes.

Macrophages transmit human immunodeficiency virus type 1 products to CD4-negative cells: involvement of matrix metalloproteinase 9

It was previously reported that human immunodeficiency virus type 1 (HIV-1) spreads in CD4 lymphocytes through cell-to-cell transmission. Here we report that HIV-1-infected macrophages, but not lymphocytes, transmit HIV-1 products to CD4-negative cells of either epithelial, neuronal, or endothelial origin in the absence of overt HIV-1 infection. This phenomenon was detectable as early as 1 h after the start of cocultivation and depended on cell-to-cell contact but not on the release of viral particles from donor cells. Transfer of HIV-1 products occurred upon their polarization and colocalization within zones of cell-to-cell contact similar to virological synapses. Neither HIV-1 Env nor Nef expression was required but, interestingly, we found that an HIV-1-dependent increase in matrix metalloproteinase 9 production from donor cells significantly contributed to the cell-to-cell transmission of the viral products. The macrophage-driven transfer of HIV-1 products to diverse CD4-negative cell types may have a significant role in AIDS pathogenesis.

Antiretroviral therapy inhibits matrix metalloproteinase-9 from blood mononuclear cells of HIV-infected patients

OBJECTIVE

To investigate whether antiretroviral therapy (ART) influences the release of matrix metalloproteinase (MMP)-9 from peripheral blood mononuclear cells (PBMC) of HIV-infected individuals.

DESIGN

Culture supernatants were collected from PBMC isolated from 46 HIV-infected subjects and 19 healthy donors (HD). Among the HIV-infected subjects, 30 were receiving ART therapy, while 16 were naive for any ART treatment.

METHODS

Zymography of culture supernatants was followed by determination of MMP-9 using computered scanning densitometry. MMP-9 net enzymatic activity was determined by the sensitive fluorescent-activated substrate conversion assay (FASC) to complement the zymography data.

RESULTS

MMP-9 was significantly elevated in culture supernatants from PBMC of ART-naive subjects in comparison with HD. In the supernatants from 30 HIV-infected subjects receiving ART therapy, MMP-9 was significantly lower than that in those from ART-naive subjects. Analysis by the reverse transcriptase polymerase chain reaction indicated that MMP-9 expression was increased in ART-naive subjects in comparison with HD but ART induced a decrease of MMP-9 expression to levels comparable with those of HD. FASC used as a functional assay showed conversion of fluorescent gelatine in ART-naive subjects, indicating the presence of active MMP-9. By contrast, in both HD and ART-treated subjects, there was no MMP-9 activity, indicating that MMP-9 was completely blocked by binding to its natural tissue inhibitor TIMP-1.

CONCLUSIONS

The present findings show for the first time that ART can reduce the capacity of PBMC from HIV-infected patients to secrete increased amounts of MMP-9.

Advances in macrophage and dendritic cell biology in HIV-1 infection stress key understudied areas in infection, pathogenesis, and analysis of viral reservoirs

The continued quest to intervene in HIV-1 infection by halting transmission, suppressing replication, or eradicating disease in infected subjects stresses the significance of dendritic cell and macrophage biology as early and persistent players in the relationship between infection and disease. As highlighted by new data and presentations at the Sixth International Workshop on HIV and Cells of Macrophage/Dendritic Lineage and Other Reservoirs, a greater emphasis is currently underway in studying the potential of targeting these cell types by intervention early in infection, better defining viral phenotypes and entry mechanisms with a more precise nomenclature system, identifying new, intrinsic cellular factors that may restrict infection within these cell types, and pursuing novel roles for macrophage activation and trafficking. Other key areas include examination of these cells as sources of viral persistence in patients, their roles in coinfection, and their metabolic function in HIV pathogenesis and drug toxicity. This issue of JLB contains reviews and original research reports from the workshop, which highlight new findings, current research questions, and key areas in need of future investigation as a result of their significance to HIV prevention and pathogenesis.