Up-Regulation of Proteinase-Activated Receptor 1 Expression in Astrocytes During HIV Encephalitis

Abstract

Proteinase-activated receptor 1 (PAR-1) is a G protein-coupled receptor that is activated by thrombin and is implicated in the pathogenesis of inflammation. Although PAR-1 is expressed on immunocompetent cells within the brain such as astrocytes, little is known about its role in the pathogenesis of inflammatory brain diseases. Herein, we investigated PAR-1 regulation of brain inflammation by stimulating human astrocytic cells with thrombin or the selective PAR-1-activating peptide. Activated cells expressed significantly increased levels of IL-1β, inducible NO synthase, and PAR-1 mRNA. Moreover, supernatants of these same cells were neurotoxic, which was inhibited by an N-methyl-d-aspartate receptor antagonist. Striatal implantation of the PAR-1-activating peptide significantly induced brain inflammation and neurobehavioral deficits in mice compared with mice implanted with the control peptide or saline. Since HIV-related neurological disease is predicated on brain inflammation and neuronal injury, the expression of PAR-1 in HIV encephalitis (HIVE) was investigated. Immunohistochemical analysis revealed that PAR-1 and (pro)-thrombin protein expression was low in control brains, but intense immunoreactivity was observed on astrocytes in HIVE brains. Similarly, PAR-1 and thrombin mRNA levels were significantly increased in HIVE brains compared with control and multiple sclerosis brains. These data indicated that activation and up-regulation of PAR-1 probably contribute to brain inflammation and neuronal damage during HIV-1 infection, thus providing new therapeutic targets for the treatment of HIV-related neurodegeneration.

A1 Adenosine Receptor Upregulation and Activation Attenuates Neuroinflammation and Demyelination in a Model of Multiple Sclerosis

“…All mouse primer sequences were established previously (Overbergh et al, 1999;Sun et al, 2001), except for A2aAR (5Ј-CGCCATCCCATTCGCCATCAC-3Ј and 5Ј-CCTTCGCCTTCATACCCGTCACCA-3Ј), A3AR (5Ј-GCCTTCGC-ATGTGGTATCAGTAAA-3Ј and 5Ј-GAAGGGCAGAGTCCGTGGT-AATC-3Ј), and MMP-12 (5Ј-TTTCTTCCATATGGCCAAGC-3Ј and 5Ј-GGTCAAAGACAGCTGCATCA-3Ј). All human primer sequence were reported previously (Boven et al, 2003), except for A1AR (5Ј-CCCCCTCGCCATCCTCATCA-3Ј and 5Ј-GCCCGCTCCACCGCA-CTC-3Ј) and MMP-12 (5Ј-GGGGCCCGTATGGAGGAAACA-3Ј and 5Ј-CACGGGCAAAAACCACCAAAATG-3Ј). Semiquantitative analysis was performed by monitoring in real-time the increase of fluorescence of the SYBR-green dye (Molecular Probes) on a Bio-Rad (Hercules, CA) i-Cycler.…”

RON Receptor Tyrosine Kinase, a Negative Regulator of Inflammation, Inhibits HIV-1 Transcription in Monocytes/Macrophages and Is Decreased in Brain Tissue from Patients with AIDS

“…The brain tissues used in these experiments have been described in previous reports (30,31) and were obtained from the AIDS Brain Bank at St. Paul's Hospital (Vancouver, Canada) and the Neurovirology Laboratory Brain Bank at the University of Calgary. Samples represented frontal white matter that was collected at autopsy from all experimental groups and stored at Ϫ80°C.…”

“…Primary Abs were detected with biotinylated goat anti-rabbit or biotinylated goat anti-mouse Abs, followed by avidin-biotin-peroxidase complexes. Peroxidase activity was detected by diaminobenzidine or alkaline phosphatase (Vector Laboratories, Burlingame, CA), as previously reported (31). Hematoxylin was used to counterstain sections to assist in identifying cells expressing RON.…”

Proteinase-Activated Receptor-2 Induction by Neuroinflammation Prevents Neuronal Death during HIV Infection

“…PAR-1 has also been implicated in the pathogenesis of neuroinflammatory/degenerative disorders (13,14). Previous studies from our group demonstrated an important role for astrocytic PAR-1 up-regulation and activation in the neuropathogenesis of HIV-1 infection (15), characterized by neuroinflammation and neuronal injury. Indeed, neuronal dysfunction and death likely underlie the motor, behavioral, and cognitive impairments that are present among patients with HIV-associated dementia (HAD), which usually becomes manifest during AIDS.…”