Cirino Thomas J, Alleyne Amy R, Duarte Vinicius, Figueroa Ariana, Simons Chloe A, Anceaume Emet M, Kendrick Justin, Wallman Olivia, Eans Shainnel O, Stacy Heather M, Medina Jessica M, McLaughlin Jay P
Department of Pharmacodynamics, College of Pharmacy, University of Florida, 1345 Center Drive, P.O. Box 100487, Gainesville, FL, 32610, USA.
Department of Neurology, University of California San Francisco, 675 Nelson Rising Lane, San Francisco, California, 94158, USA.
J Neuroimmune Pharmacol. 2022 Jun;17(1-2):152-164. doi: 10.1007/s11481-021-09985-4. Epub 2021 Feb 22.
Despite the success of combined antiretroviral therapy (cART) in reducing viral load, a substantial portion of Human Immunodeficiency Virus (HIV)+ patients report chronic pain. The exact mechanism underlying this co-morbidity even with undetectable viral load remains unknown, but the transactivator of transcription (HIV-Tat) protein is of particular interest. Functional HIV-Tat protein is observed even in cerebrospinal fluid of patients who have an undetectable viral load. It is hypothesized that Tat protein exposure is sufficient to induce neuropathic pain-like manifestations via both activation of microglia and generation of oxidative stress. iTat mice conditionally expressed Tat protein in the central nervous system upon daily administration of doxycycline (100 mg/kg/d, i.p., up to 14 days). The effect of HIV-Tat protein exposure on the well-being of the animal was assessed using sucrose-evoked grooming and acute nesting behavior for pain-depressed behaviors, and the development of hyperalgesia assessed with warm-water tail-withdrawal and von Frey assays for thermal hyperalgesia and mechanical allodynia, respectively. Tissue harvested at select time points was used to assess ex vivo alterations in oxidative stress, astrocytosis and microgliosis, and blood-brain barrier integrity with assays utilizing fluorescence-based indicators. Tat protein induced mild thermal hyperalgesia but robust mechanical allodynia starting after 4 days of exposure, reaching a nadir after 7 days. Changes in nociceptive processing were associated with reduced sucrose-evoked grooming behavior without altering acute nesting behavior, and in spinal cord dysregulated free radical generation as measured by DCF fluorescence intensity, altered immunohistochemical expression of the gliotic markers, Iba-1 and GFAP, and increased permeability of the blood-brain barrier to the small molecule fluorescent tracer, sodium fluorescein, in a time-dependent manner. Pretreatment with the anti-inflammatory, indomethacin (1 mg/kg/d, i.p.), the antioxidant, methylsulfonylmethane (100 mg/kg/d i.p.), or the immunomodulatory agent, dimethylfumarate (100 mg/kg/d p.o.) thirty minutes prior to daily injections of doxycycline (100 mg/kg/d i.p.) over 7 days significantly attenuated the development of Tat-induced mechanical allodynia. Collectively, the data suggests that even acute exposure to HIV-1 Tat protein at pathologically relevant levels is sufficient to produce select neurophysiological and behavioral manifestations of chronic pain consistent with that reported by HIV-positive patients.
尽管联合抗逆转录病毒疗法（cART）在降低病毒载量方面取得了成功，但仍有相当一部分人类免疫缺陷病毒（HIV）阳性患者报告有慢性疼痛。即使病毒载量检测不到，这种合并症背后的确切机制仍然未知，但转录激活因子（HIV-Tat）蛋白尤其值得关注。即使在病毒载量检测不到的患者脑脊液中也能观察到功能性HIV-Tat蛋白。据推测，Tat蛋白暴露足以通过激活小胶质细胞和产生氧化应激来诱导神经性疼痛样表现。iTat小鼠在每天给予强力霉素（100 mg/kg/d，腹腔注射，最多14天）后，在中枢神经系统中条件性表达Tat蛋白。使用蔗糖诱发的梳理行为和急性筑巢行为来评估HIV-Tat蛋白暴露对动物健康的影响，以检测疼痛抑制行为，分别用温水甩尾试验和von Frey试验评估痛觉过敏的发展，以检测热痛觉过敏和机械性异常性疼痛。在选定的时间点采集组织，用于通过基于荧光指示剂的检测来评估氧化应激、星形细胞增生和小胶质细胞增生的离体变化以及血脑屏障的完整性。Tat蛋白在暴露4天后开始诱导轻度热痛觉过敏，但在7天后达到最低点时诱导强烈的机械性异常性疼痛。伤害性处理的变化与蔗糖诱发的梳理行为减少有关，但不改变急性筑巢行为，并且脊髓中通过DCF荧光强度测量的自由基生成失调，胶质细胞标记物Iba-1和GFAP的免疫组化表达改变，以及血脑屏障对小分子荧光示踪剂荧光素钠的通透性随时间增加。在每天注射强力霉素（100 mg/kg/d，腹腔注射）前30分钟，用抗炎药吲哚美辛（1 mg/kg/d，腹腔注射）、抗氧化剂甲基磺酰甲烷（100 mg/kg/d，腹腔注射）或免疫调节剂富马酸二甲酯（100 mg/kg/d，口服）进行预处理，持续7天，可显著减轻Tat诱导的机械性异常性疼痛的发展。总体而言，数据表明，即使在病理相关水平急性暴露于HIV-1 Tat蛋白也足以产生与HIV阳性患者报告一致的慢性疼痛的特定神经生理和行为表现。
