Post-transcriptional Regulation of Astrocyte-Tissue Inhibitor of Metalloproteinases-1 (TIMP-1) In HIV-Associated Neurocognitive Disorders

HIV-1 leads to several central nervous system (CNS) problems termed as HIV-associated neurocognitive disorders (HAND). Tissue inhibitor of metallopoteinases-1 (TIMP-1) / matrix metalloproteinase (MMP) imbalance has been observed in HAND and several other neuroinflammatory conditions. Astrocytes are major contributors to brain TIMPs, and they regulate TIMP / MMP balance [1, 2]. Differential regulation of TIMP-1 in acute versus chronic neuroinflammation is relevant to HAND neuropathogenesis and long-term neurodegeneration[3]. However, the underlying mechanisms are still being uncovered. Our previous work has shown the neuroprotective role of TIMP-1 via MMPdependent and independent manners [4, 5]. In this study, we investigated regulation of astrocyte TIMP-1 in HAND. First, microarray analyses were performed to analyze micro RNA (miRNA) changes in IL-1β activated astrocytes. For further studies, TIMP-1 3’ untranslated region (TIMP-1 3’UTR) cloned downstream of firefly luciferase and miRNA overexpression constructs were used to investigate miRNA-mediated TIMP-1 3’UTR post-transcriptional regulation. Firefly luciferase activity and endogenous astrocyte TIMP-1 levels were measured in parallel experiments. A total of 12 miRNAs were significantly increased and four were significantly decreased; seven of those were further confirmed by real-time PCR (RT2-PCR). The most increased were miR 155, miR 146b and miR 29b, whereas, the most downregulated one was miR 518e. Overexpression of miR 155, miR 146b, miR 29b altered both firefly luciferase activity via and endogenous astrocyte TIMP-1 levels in IL-1β and/or HIV-1 activated astrocytes. Comparable responses were obtained in luciferase activity changes and de novo TIMP- 1 protein levels corroborating post-transcriptional regulation of astrocyte-TIMP-1. Thus, our data suggests that astrocyte-TIMP-1 is regulated post-transcriptionally by miRNAs during HAND. Given the emerging role of miRNAs in several neuroinflammatory and neurodegenerative diseases, our data uncover a novel mechanism of TIMP-1 regulation in astrocytes that may have significant impact on future studies on MMP/TIMP balance in HIV-associated neuroinflammation.