MCP-3/CCL7 production by astrocytes: implications for SIV neuroinvasion and AIDS encephalitis.

Monocyte/macrophages and activated lymphocytes traffic through normal brain, and this trafficking is increased in inflammatory conditions such as HIV encephalitis (HIVE). HIVE is characterized in part by perivascular accumulations of macrophages. The earliest events in this process are poorly understood and difficult or impossible to address in humans. The SIV-infected macaque model of neuroAIDS has demonstrated migration of monocytes into the brain early in disease, coincident with peak SIV viremia. The chemotactic signals that initiate the increased emigration of mononuclear cells into the CNS have not been described. Here, we describe astrocytes as a primary source of chemokines to facilitate basal levels of monocyte trafficking to CNS and that increased chemokine (C-C motif) ligand 7 (CCL7) production may be responsible for initiating the increased trafficking in neuroAIDS. We have previously published complementary in vivo work demonstrating the presence of monocyte chemoattractant protein 3 (MCP-3)/CCL7 within the brain of SIV-infected macaques. Here, we demonstrate that MCP-3/CCL7 is a significant chemokine produced by astrocytes, that basal monocyte migration may be facilitated by astrocyte-derived CCL7, that production of CCL7 is rapidly increased by TNF-α and thus likely plays a critical role in initiating neuroinvasion by SIV/HIV.

Association of FAK activation with lentivirus-induced disruption of blood-brain barrier tight junction-associated ZO-1 protein organization.

Expression of tight junction proteins between brain microvascular endothelial cells (BMECs) of the blood-brain barrier (BBB) is lost during development of human immunodeficiency virus (HIV) encephalitis (HIVE). Although many studies have focused on the strains of virus that induce neurological sequelae or on the macrophages/microglia that are associated with development of encephalitis, the molecular signaling pathways within the BMECs involved have yet to be resolved. We have previously shown that there is activation and disruption of an in vitro BBB model using lentivirus-infected CEMx174 cells. We and others have shown similar disruption in vivo. Therefore, it was of interest to determine if the presence of infected cells could disrupt intact cerebral microvessels immediately ex vivo, and if so, which signaling pathways were involved. The present data demonstrate that disruption of tight junctions between BMECs is mediated through activation of focal adhesion kinase (FAK) by phosphorylation at TYR-397. Inhibition of FAK activation is sufficient to prevent tight junction disruption. Thus, it may be possible to inhibit the development of HIVE by using inhibitors of FAK.

Acquired immunodeficiency syndrome and the blood-brain barrier.

The blood-brain barrier (BBB) plays a critical role in normal physiology of the central nervous system by regulating what reaches the brain from the periphery. The BBB also plays a major role in neurologic disease including neuropathologic sequelae associated with infection by human immunodeficiency virus (HIV) in humans and the closely related simian immunodeficiency virus (SIV) in macaques. In this review, we provide an overview of the function, structure, and components of the BBB, followed by a more detailed discussion of the subcellular structures and regulation of the tight junction. We then discuss the ways in which HIV/SIV affects the BBB, largely through infection of monocytes/macrophages, and how infected macrophages crossing the BBB ultimately results in breakdown of the barrier.

Cyclooxygenase-1-deficient mice have high sleep-to-wake blood pressure ratios and renal vasoconstriction.

We used cyclooxygenase-1 (COX-1)-deficient mice to test the hypothesis that COX-1 regulates blood pressure (BP) and renal hemodynamics. The awake time (AT) mean arterial pressures (MAPs) measured by telemetry were not different between COX-1(+/+) and COX-1(-/-) (131+/-2 versus 126+/-3 mm Hg; NS). However, COX-1(-/-) had higher sleep time (ST) MAP (93+/-1 versus 97+/-2 mm Hg; P<0.05) and sleep-to-awake BP ratio (+8.6%; P<0.05). Under anesthesia with moderate sodium loading, COX-1(-/-) had higher MAP (109+/-5 versus 124+/-4 mm Hg; P<0.05), renal vascular resistance (23.5+/-1.6 versus 30.7+/-1.7 mm Hg . mL(-1) . min(-1) . g(-1); P<0.05) and filtration fraction (33.7+/-2.1 versus 40.2+/-2.0%; P<0.05). COX-1(-/-) had a 89% reduction (P<0.0001) in the excretion of TxB2, a 76% reduction (P<0.01) in PGE2, a 40% reduction (P<0.0002) in 6-ketoPGF1alpha (6keto), a 27% reduction (P<0.02) in 11-betaPGF2alpha (11beta), a 35% reduction (P<0.01) in nitrate plus nitrite (NOx), and a 52% increase in metanephrine (P<0.02). The excretion of normetanephrine, a marker for sympathetic nervous activity, was reduced during ST in COX-1(+/+) (6.9+/-0.9 versus 3.2+/-0.6 g . g(-1) creatinine . 10(-3); P<0.01). This was blunted in COX-1(-/-) (5.1+/-0.9 versus 4.9+/-0.7 g . g(-1) creatinine . 10(-3); NS). Urine collection during ST showed lower excretion of 6keto, 11beta, NOx, aldosterone, sodium, and potassium than during AT in both COX-1(+/+) and COX-1(-/-), and there were positive correlations among these parameters (6keto versus NOx; P<0.005; 11beta versus NOx; P<0.005; and NOx versus sodium; P<0.005). In conclusion, COX-1 mediates a suppressed sympathetic nervous activity and enhanced NO, which may contribute to renal vasodilatation and a reduced MAP while asleep or under anesthesia. COX-1 contributes to the normal nocturnal BP dipping phenomenon.