Background Mechanisms for increased cardiovascular risk in HIV-1-infected adults are incompletely understood, but platelet activation and immune activation leading to a prothrombotic state have been proposed as significant contributors. Aspirin has antiplatelet and immunomodulatory properties. We explored whether 1 week of low-dose aspirin attenuates platelet activation and immune activation in HIV-1-infected and virologically suppressed adults on antiretroviral therapy. Methods Platelet activation and immune activation were measured in HIV-1-infected subjects virologically suppressed on antiretroviral therapy and controls before and after 1 week of low-dose aspirin. Results Compared with control subjects, HIV-1-infected subjects had increased platelet activation, as measured by spontaneous platelet aggregation and aggregation in response to adenosine diphosphate, collagen, and arachidonic acid. After aspirin therapy, percent aggregation decreased similarly in both HIV-1-infected and control subjects to all platelet agonists tested except aggregation in response to arachidonic acid, which remained elevated in the HIV-1-infected group. HIV-1-infected subjects exhibited increased markers of T-cell activation (CD38 and HLA-DR) and monocyte activation (sCD14), which decreased after 1 week of aspirin therapy. Moreover, leukocyte responses to Toll-like receptor stimulation were enhanced after 1 week of aspirin therapy. In vitro studies showed that HIV-1 plasma could activate healthy platelets, which in turn activated monocytes, implicating a direct role for activated platelets in immune activation. Conclusions Our data demonstrate that heightened platelet activation and immune activation in treated HIV-1 disease are attenuated by 1 week of aspirin therapy. Aspirin should be further studied for its antithrombotic and immunomodulatory benefits in treated HIV-1 disease.

No abstract

Some studies suggest that mean platelet volume (MPV) correlates with increased risk for cardiovascular morbidity and mortality. In this study, we aim to assess reproducibility, need for standardized measurements, effect of aspirin, and association with other established markers of platelet activity. Following an overnight fast, 48 healthy volunteers had weekly assessment of platelet activity and were administered aspirin 81 mg daily for 7 d between weeks 3 and 4. We investigated the influence of time between phlebotomy and MPV measurement (n=10). Reproducibility was assessed by coefficient of variation (CV) and intraclass correlation coefficient (ICC). MPV measurements were reproducible (Week 1: 10.6 fL [9.9–11], Week 2: 10.6 fL [10.0–10.9], Week 3: 10.6 fL [9.8–11]). CV was ≤4% and ICC>0.85 (p<0.001) for each comparison, indicating excellent reproducibility. There was no effect of aspirin on MPV (10.6 fL [9.8–11] versus 10.5 fL [9.9–11]; p=0.81). MPV significantly increased as time between phlebotomy and MPV measurement increased (Spearman’s rho=0.94, p=0.001). Increasing MPV tertiles was associated with collagen- and thrombin receptor-activated peptide-induced platelet aggregation but not with ADP- or arachidonic acid-induced or spontaneous platelet aggregation. In conclusion, when standardized, MPV is a reproducible marker of platelet size and not affected by low-dose aspirin. MPV is modestly associated with some, but not all, markers of platelet activity.

Astrocyte swelling (cytotoxic brain edema) is the major neurological complication of acute liver failure (ALF), a condition in which ammonia has been strongly implicated in its etiology. Ion channels and transporters are known to be involved in cell volume regulation and a disturbance in these systems may result in cell swelling. One ion channel known to contribute to astrocyte swelling/brain edema in other neurological disorders is the ATP-dependent, non-selective cation channel (NCCa-ATP channel). We therefore examined its potential role in the astrocyte swelling/brain edema associated with ALF. Cultured astrocytes treated with 5 mM ammonia showed a 3-fold increase in the sulfonylurea receptor type 1 (SUR1) protein expression, a marker of NCCa-ATP channel activity. Blocking SUR1 with glibenclamide significantly reduced the ammonia-induced cell swelling in cultured astrocytes. Additionally, overexpression of SUR1 in ammonia-treated cultured astrocytes was significantly reduced by co-treatment of cells with BAY 11-7082, an inhibitor of NF-κB, indicating the involvement of an NF-κB-mediated SUR1 upregulation in the mechanism of ammonia-induced astrocyte swelling. Brain SUR1 mRNA level was also found to be increased in the thioacetamide (TAA) rat model of ALF. Additionally, we found a significant increase in SUR1 protein expression in rat brain cortical astrocytes in TAA-treated rats. Treatment with glibenclamide significantly reduced the brain edema in this model of ALF. These findings strongly suggest the involvement of NCCa-ATP channel in the astrocyte swelling/brain edema in ALF, and that targeting this channel may represent a useful approach for the treatment of the brain edema associated with ALF.

OBJECTIVE Plasma soluble CD40L (sCD40L) is increased during human immunodeficiency virus-1 (HIV) infection, but it is unknown whether it circulates in monomeric or multimeric forms, and whether the circulating forms have differential effects on myeloid dendritic cell (DC) function and adaptive regulation. DESIGN sCD40L forms were measured in plasma samples from HIV-infected donors. The effects of sCD40L forms on DC function were measured in vitro. METHODS To delineate which forms of sCD40L are present in plasma from HIV-infected donors, immunoblots were performed following enrichment of plasma for medium and low abundance proteins. DCs from seronegative donors were exposed to multiple forms of sCD40L prior to Toll-like receptor (TLR) stimulation and DC function and adaptive regulation was assessed in vitro. RESULTS Monomeric and multimeric forms of sCD40L were identified in plasma from ART-treated HIV-infected donors. Though monomeric and multimeric forms of sCD40L had differential effects on DC activation when given alone, both strongly suppressed secretion of the Th1 skewing cytokine, IL-12, upon subsequent TLR stimulation. Furthermore, DCs exposed to both monomeric and multimeric sCD40L induced regulatory T cell formation and T cell anergy. CONCLUSIONS Elevated sCD40L during HIV infection impairs DC function, contributing to innate and adaptive immune dysfunction. Antiretroviral adjunctive therapies that decrease sCD40L may provide immune modulatory benefits.