Infusion of HIV-1 Nef-expressing astrocytes into the rat hippocampus induces enteropathy and interstitial pneumonitis and increases blood–brain-barrier permeability

Abstract

Even though HIV-1 replication can be suppressed by combination antiretroviral therapy (cART) inflammatory processes still occur, contributing to comorbidities. Comorbidities are attributed to variety of factors, including HIV-1 mediated inflammation. Several HIV-1 proteins mediate central nervous system (CNS) inflammation, including Nef. Nef is an early HIV-1 protein, toxic to neurons and glia and is sufficient to cause learning impairment similar to some deficits observed in HIV-1 associated neurocognitive disorders. To determine whether hippocampal Nef expression by astrocytes contributes to comorbidities, specifically peripheral inflammation, we infused Sprague Dawley rats with GFP- (control) or Nef-transfected astrocytes into the right hippocampus. Brain, lung, and ileum were collected postmortem for the measurement of inflammatory markers. Increased blood-brain-barrier permeability and serum IL-1β levels were detected in the Nef-treated rats. The lungs of Nef-treated rats demonstrated leukocyte infiltration, macrophage upregulation, and enhanced vascular permeability. Ileal tissue showed reactive follicular lymphoid hyperplasia, increased permeability and macrophage infiltration. The intracerebroventricular application of IL-1 receptor antagonist reduced infiltration of immune cells into ileum and lung, indicating the important role of IL-1β in mediating the spread of inflammation from the brain to other tissues. This suggests that localized expression of a single viral protein, HIV-1 Nef, can contribute to a broader inflammatory response by upregulation of IL-1β. Further, these results suggest that Nef contributes to the chronic inflammation seen in HIV patients, even in those whose viremia is controlled by cART.

Blockade of beta adrenergic receptors protects the blood brain barrier and reduces systemic pathology caused by HIV-1 Nef protein

“…To verify the in-vivo expression, we performed ELISA of Nef in serum. ELISA was selected based on our earlier reports that transfected astrocytes secrete Nef [ 27 ], and that such astrocytic Nef expression compromises the BBB according to Evans blue dye extravasation and reduction of the tight junction protein claudin-5 [ 10 ]. ELISA shows only background expression (~0.2ng/ml) in naïve animals (data not shown), while Nef-treated animals, independent of propranolol administration, showed no significant difference in serum Nef, Fig 1(D) .…”

“…The blood brain barrier (BBB) integrity is known to be reduced due to tight junction protein disruption by several HIV proteins, and thereby a compromised BBB may cause inflammatory cytokines to cross over more abundantly from the periphery to the brain [ 7 – 10 ]. Cytokines such as interleukin IL-1β or TNF-α are inflammatory communicators from the immune system to the central nervous system (CNS) [ 11 ].…”

“…However, most studies concentrate on the effect of Nef in the brain, with few studies examining how those effects extend to the periphery. Recently, we demonstrated that the astrocytic expression of Nef could lead to BBB disruption, claudin-5 reduction, elevated serum IL-1β, and upregulated expression of macrophages in the lung and ileum of rats exposed to the protein [ 10 ]. Therefore, the pathway by which centrally expressed Nef could be inducing systemic inflammation is an area of interest.…”

“…In the present study which is a follow up to our earlier work with this model [ 10 , 27 ], we aimed to characterize the role of Nef in the activation of the SNS response. We chose to study the beta-adrenergic receptors (β-ARs) since activation of the G protein-coupled stimulatory receptor (GPCR) mediates the release of several inflammatory cytokine through activation of the NF-κB pathway [ 31 ].…”

Alzheimer’s-Like Pathology at the Crossroads of HIV-Associated Neurological Disorders

“…Other HIV proteins also affect BBB permeability. For example, the early protein Nef, expressed by astrocytes, has been shown to exacerbate BBB disruption [ 188 ]. Nef-transfected microglia have similar effects on the BBB, with alleviation seen via the use of Nef peptides [ 189 ].…”