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Open Access Research

Transient hypercapnia reveals an underlying cerebrovascular pathology in a murine model for HIV-1 associated neuroinflammation: role of NO-cGMP signaling and normalization by inhibition of cyclic nucleotide phosphodiesterase-5

Jharon Silva1, Oksana Polesskaya1, Walter Knight34, Johnny Ting Zheng1, Megan Granger1, Tenée Lopez5, Fernando Ontiveros1, Changyong Feng2, Chen Yan34, Karl A Kasischke6 and Stephen Dewhurst1*

Author Affiliations

1 Department of Microbiology and Immunology, University of Rochester Medical Center, 601 Elmwood Avenue, Box 672, Rochester, NY 14642, USA

2 Department of Biostatistics and Computational Biology, University of Rochester Medical Center, 601 Elmwood Avenue, Box 631, Rochester, NY, USA

3 Department of Medicine, University of Rochester Medical Center, 601 Elmwood Avenue, Box MED, Rochester, NY, USA

4 Aab Cardiovascular Research Institute, University of Rochester Medical Center, 601 Elmwood Avenue, Box CVRI, Rochester, NY, USA

5 University of Houston, Houston, TX, USA

6 Dept. of Neurology, University of Ulm Medical Center, Ulm, Germany

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Journal of Neuroinflammation 2012, 9:253  doi:10.1186/1742-2094-9-253

Published: 20 November 2012

Abstract

Background

Cerebral blood flow (CBF) is known to be dysregulated in persons with human immunodeficiency virus 1 (HIV-1), for uncertain reasons. This is an important issue because impaired vasoreactivity has been associated with increased risk of ischemic stroke, elevated overall cardiovascular risk and cognitive impairment.

Methods

To test whether dysregulation of CBF might be due to virally-induced neuroinflammation, we used a well-defined animal model (GFAP-driven, doxycycline-inducible HIV-1 Tat transgenic (Tat-tg) mice). We then exposed the mice to a brief hypercapnic stimulus, and assessed cerebrovascular reactivity by measuring 1) changes in cerebral blood flow, using laser Doppler flowmetry and 2) changes in vascular dilation, using in vivo two-photon imaging.

Results

Exposure to brief hypercapnia revealed an underlying cerebrovascular pathology in Tat-tg mice. In control animals, brief hypercapnia induced a brisk increase in cortical flow (20.8% above baseline) and vascular dilation, as measured by laser Doppler flowmetry and in vivo two-photon microscopy. These responses were significantly attenuated in Tat-tg mice (11.6% above baseline), but cortical microvascular morphology and capillary density were unaltered, suggesting that the functional pathology was not secondary to vascular remodeling. To examine the mechanistic basis for the diminished cerebrovascular response to brief hypercapnia, Tat-tg mice were treated with 1) gisadenafil, a phosphodiesterase 5 (PDE5) inhibitor and 2) tetrahydrobiopterin (BH4). Gisadenafil largely restored the normal increase in cortical flow following hypercapnia in Tat-tg mice (17.5% above baseline), whereas BH4 had little effect. Gisadenafil also restored the dilation of small (<25 μm) arterioles following hypercapnia (19.1% versus 20.6% diameter increase in control and Tat-tg plus gisadenafil, respectively), although it failed to restore full dilation of larger (>25 μm) vessels.

Conclusions

Taken together, these data show that HIV-associated neuroinflammation can cause cerebrovascular pathology through effects on cyclic guanosine monophosphate (cGMP) metabolism and possibly on PDE5 metabolism.

Keywords:
Cerebrovascular reactivity; HIV-1; Tat-transgenic mice; Hypercapnia; Phosphodiesterase-5