title: Direct effects of HIV-1 Tat on excitability and survival of primary dorsal root ganglion neurons: possible contribution to HIV-1-associated pain.
abstract: The vast majority of people living with human immunodeficiency virus type 1 (HIV-1) have pain syndrome, which has a significant impact on their quality of life. The underlying causes of HIV-1-associated pain are not likely attributable to direct viral infection of the nervous system due to the lack of evidence of neuronal infection by HIV-1. However, HIV-1 proteins are possibly involved as they have been implicated in neuronal damage and death. The current study assesses the direct effects of HIV-1 Tat, one of potent neurotoxic viral proteins released from HIV-1-infected cells, on the excitability and survival of rat primary dorsal root ganglion (DRG) neurons. We demonstrated that HIV-1 Tat triggered rapid and sustained enhancement of the excitability of small-diameter rat primary DRG neurons, which was accompanied by marked reductions in the rheobase and resting membrane potential (RMP), and an increase in the resistance at threshold (R(Th)). Such Tat-induced DRG hyperexcitability may be a consequence of the inhibition of cyclin-dependent kinase 5 (Cdk5) activity. Tat rapidly inhibited Cdk5 kinase activity and mRNA production, and roscovitine, a well-known Cdk5 inhibitor, induced a very similar pattern of DRG hyperexcitability. Indeed, pre-application of Tat prevented roscovitine from having additional effects on the RMP and action potentials (APs) of DRGs. However, Tat-mediated actions on the rheobase and R(Th) were accelerated by roscovitine. These results suggest that Tat-mediated changes in DRG excitability are partly facilitated by Cdk5 inhibition. In addition, Cdk5 is most abundant in DRG neurons and participates in the regulation of pain signaling. We also demonstrated that HIV-1 Tat markedly induced apoptosis of primary DRG neurons after exposure for longer than 48 h. Together, this work indicates that HIV-1 proteins are capable of producing pain signaling through direct actions on excitability and survival of sensory neurons.
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America.
authors.forename: Xianxun
authors.initials: X
authors.lastname: Chi
authors.forename: Tohti
authors.initials: T
authors.lastname: Amet
authors.forename: Daniel
authors.initials: D
authors.lastname: Byrd
authors.forename: Kuei-Hua
authors.initials: KH
authors.lastname: Chang
authors.forename: Kavita
authors.initials: K
authors.lastname: Shah
authors.forename: Ningjie
authors.initials: N
authors.lastname: Hu
authors.forename: Ayslinn
authors.initials: A
authors.lastname: Grantham
authors.forename: Sishun
authors.initials: S
authors.lastname: Hu
authors.forename: Jianhong
authors.initials: J
authors.lastname: Duan
authors.forename: Feng
authors.initials: F
authors.lastname: Tao
authors.forename: Grant
authors.initials: G
authors.lastname: Nicol
authors.forename: Qigui
authors.initials: Q
authors.lastname: Yu
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002211:Capsaicin / Q000494:pharmacology; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D051360:Cyclin-Dependent Kinase 5 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D005727:Ganglia, Spinal / Q000166:cytology* / Q000473:pathology*; D015497:HIV-1; D008297:Male; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010146:Pain / Q000378:metabolism / Q000473:pathology* / Q000821:virology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000494:pharmacology*
chemical_list: D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D054322:tat Gene Products, Human Immunodeficiency Virus; D051360:Cyclin-Dependent Kinase 5; D002211:Capsaicin