Publications

Eccentric muscle exercise is a common cause of acute and chronic (lasting days to weeks) musculoskeletal pain. To evaluate the mechanisms involved, we have employed a model in the rat, in which eccentric hind limb exercise produces both acute mechanical hyperalgesia as well as long-term changes characterized by enhanced hyperalgesia to subsequent exposure to an inflammatory mediator. Eccentric exercise of the hind limb produced mechanical hyperalgesia, measured in the gastrocnemius muscle, which returned to baseline at 120 h post-exercise. When nociceptive thresholds had returned to baseline, intramuscular injection of prostaglandin E(2) (PGE(2) ) induced hyperalgesia that was unattenuated 240 h later, much longer than PGE(2) -induced hyperalgesia in unexercised rats (4 h). This marked prolongation of PGE(2) hyperalgesia induced by eccentric exercise was prevented by the spinal intrathecal injection of oligodeoxynucleotide antisense to protein kinase Cε, a second messenger in nociceptors implicated in the induction of chronic pain. Exercise-induced hyperalgesia and prolongation of PGE(2) hyperalgesia were inhibited by the spinal intrathecal administration of antisense for the interleukin-6 but not the tumor necrosis factor α type 1 receptor. These findings provide further insight into the mechanism underlying exercise-induced chronic muscle pain, and suggest novel approaches for the prevention and treatment of exercise- or work-related chronic musculoskeletal pain syndromes.

A major dose-limiting side effect of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) chemotherapies, such as the nucleoside reverse transcriptase inhibitors (NRTIs), is a small-fiber painful peripheral neuropathy, mediated by its mitochondrial toxicity. Co-morbid conditions may also contribute to this dose-limiting effect of HIV/AIDS treatment. Alcohol abuse, which alone also produces painful neuropathy, is one of the most important co-morbid risk factors for peripheral neuropathy in patients with HIV/AIDS. Despite the prevalence of this problem and its serious impact on the quality of life and continued therapy in HIV/AIDS patients, the mechanisms by which alcohol abuse exacerbates highly active antiretroviral therapy (HAART)-induced neuropathic pain has not been demonstrated. In this study, performed in rats, we investigated the cellular mechanism by which consumed alcohol impacts antiretroviral-induced neuropathic pain. NRTI 2',3'-dideoxycytidine (ddC; 50 mg/kg) neuropathy was mitochondrial-dependent and PKCε-independent, and alcohol-induced painful neuropathy was PKCε-dependent and mitochondrial-independent. At low doses, ddC (5 mg/kg) and alcohol (6.5% ethanol diet for 1 week), which alone do not affect nociception, together produce profound mechanical hyperalgesia. This hyperalgesia is mitochondrial-dependent but PKCε-independent. These experiments, which provide the first model for studying the impact of co-morbidity in painful neuropathy, support the clinical impression that alcohol consumption enhances HIV/AIDS therapy neuropathy, and provide evidence for a role of mitochondrial mechanisms underlying this interaction.

Phospholipids are required for epidermal lamellar body formation. Glycerol 3-phosphate acyltransferases (GPATs) catalyze the initial step in the biosynthesis of glycerolipids. Little is known about the expression and regulation of GPATs in epidermis/keratinocytes. Here, we demonstrate that GPAT 1, 3, and 4 are expressed in epidermis/keratinocytes, whereas GPAT2 is not detected. In mouse epidermis, GPAT 3 and 4 are mainly localized to the upper layers whereas GPAT1 is found in both the upper and lower layers. GPAT1 and 3 mRNA increase during fetal rat epidermal development. No change in GPAT expression was observed in adult mice following acute permeability barrier disruption. Calcium-induced human keratinocyte differentiation increased GPAT3 mRNA whereas both GPAT1 and 4 mRNA levels decreased. In parallel, total GPAT activity increased 2-fold in differentiated keratinocytes attributable to an increase in N-ethylmaleimide (NEM) sensitive GPAT activity localized to microsomes with little change in NEM resistant activity, consistent with an increase in GPAT3. Furthermore, PPARγ or PPARδ activators increased GPAT3 mRNA, microsomal GPAT activity, and glycerol lipid synthesis without affecting the expression of GPAT1 or 4. Finally, both PPARγ and PPARδ activators increased GPAT3 mRNA via increasing its transcription. Thus, multiple isoforms of GPAT are expressed and differentially regulated in epidermis/keratinocytes.

A small percentage of human immunodeficiency virus (HIV)-infected individuals, termed elite controllers, are able to spontaneously control HIV replication in blood. As the gastrointestinal mucosa is an important site of HIV transmission and replication as well as CD4+ T-cell depletion, it is important to understand the nature of the immune responses occurring in this compartment. Although the role of the HIV-specific CD8+ T-cell responses in mucosal tissues has been described, few studies have investigated the role of mucosal HIV-specific CD4+ T cells. In this study, we assessed HIV-specific CD4+ T-cell responses in the rectal mucosa of 28 "controllers" (viral load [VL] of <2,000 copies/ml), 14 "noncontrollers" (VL of >10,000 copies/ml), and 10 individuals on highly active antiretroviral therapy (HAART) (VL of <75 copies/ml). Controllers had higher-magnitude Gag-specific mucosal CD4+ T-cell responses than individuals on HAART (P<0.05), as measured by their ability to produce gamma interferon (IFN-γ), interleukin-2 (IL-2), tumor necrosis factor alpha (TNF-α), and macrophage inflammatory protein 1β (MIP-1β). The frequency of polyfunctional mucosal CD4+ T cells was also higher in controllers than in noncontrollers or individuals on HAART (P<0.05). Controllers with the strongest HIV-specific CD4+ T-cell responses possessed class II HLA alleles, HLA-DRB1*13 and/or HLA-DQB1*06, previously associated with a nonprogression phenotype. Strikingly, individuals with both HLA-DRB1*13 and HLA-DQB1*06 had highly polyfunctional mucosal CD4+ T cells compared to individuals with HLA-DQB1*06 alone or other class II alleles. The frequency of polyfunctional CD4+ T cells in rectal mucosa positively correlated with the magnitude of the mucosal CD8+ T-cell response (Spearman's r=0.43, P=0.005), suggesting that increased CD4+ T-cell "help" may be important in maintaining strong CD8+ T-cell responses in the gut of HIV controllers.