Involvement of TLR2-TLR4, NLRP3, and IL-17 in pain induced by a novel Sprague-Dawley rat model of experimental autoimmune encephalomyelitis.

Up to 92% of patients suffering from multiple sclerosis (MS) experience pain, most without adequate treatment, and many report pain long before motor symptoms associated with MS diagnosis. In the most commonly studied rodent model of MS, experimental autoimmune encephalomyelitis (EAE), motor impairments/disabilities caused by EAE can interfere with pain testing. In this study, we characterize a novel low-dose myelin-oligodendrocyte-glycoprotein (MOG)-induced Sprague-Dawley (SD) model of EAE-related pain in male rats, optimized to minimize motor impairments/disabilities. Adult male SD rats were treated with increasing doses of intradermal myelin-oligodendrocyte-glycoprotein (MOG1-125) (0, 4, 8, and 16 µg) in incomplete Freund's adjuvant (IFA) vehicle to induce mild EAE. Von Frey testing and motor assessments were conducted prior to EAE induction and then weekly thereafter to assess EAE-induced pain and motor impairment. Results from these studies demonstrated that doses of 8 and 16 µg MOG1-125 were sufficient to produce stable mechanical allodynia for up to 1 month in the absence of hindpaw motor impairments/disabilities. In the follow-up studies, these doses of MOG1-125, were administered to create allodynia in the absence of confounded motor impairments. Then, 2 weeks later, rats began daily subcutaneous injections of the Toll-like receptor 2 and 4 (TLR2-TLR4) antagonist (+)-naltrexone [(+)-NTX] or saline for an additional 13 days. We found that (+)-NTX also reverses EAE-induced mechanical allodynia in the MOG-induced SD rat model of EAE, supporting parallels between models, but now allowing a protracted timecourse to be examined completely free of motor confounds. Exploring further mechanisms, we demonstrated that both spinal NOD-like receptor protein 3 (NLRP3) and interleukin-17 (IL-17) are necessary for EAE-induced pain, as intrathecal injections of NLRP3 antagonist MCC950 and IL-17 neutralizing antibody both acutely reversed EAE-induced pain. Finally, we show that spinal glial immunoreactivity induced by EAE is reversed by (+)-NTX, and that spinal demyelination correlates with the severity of motor impairments/disabilities. These findings characterize an optimized MOG-induced SD rat model of EAE for the study of pain with minimal motor impairments/disabilities. Finally, these studies support the role of TLR2-TLR4 antagonists as a potential treatment for MS-related pain and other pain and inflammatory-related disorders.

Unexplained Gait and Balance Changes: A Case Report of Myxoma Mitigation in a Breast Reduction Patient.

In Fall 2020, a female physical therapist (PT) developed mild changes in gait, infrapatellar tendon pain, and lateral patellar tracking. As a PT in good physical condition, she did not access her employer's occupational health clinic but instead she self-treated. Two months after symptom onset and self-treatment, she was diagnosed with an intramuscular myxoma within her left vastus lateralis, the largest muscle within the quadricep. The employee was at risk of slips, trips, and falls as the mass grew. Due to the location and increasing size of the mass, the employee required surgical treatment. Healthcare workers, particularly those who provide treatment, are likely to self-treat rather than seek assistance from the occupational health professional. The employee was seen by a plastic surgeon for an unrelated medical condition which is when the myxoma was diagnosed. Further delay may have led to occupational injury associated with the balance and gait disturbances. Opportunity exists for the occupational health professional to provide a review of services, including screening for musculoskeletal changes associated with occupational injury such as those described herein. This is especially important among those healthcare workers who tend to self-treat.

T cell transgressions: Tales of T cell form and function in diverse disease states.

Insights into T cell form, function, and dysfunction are rapidly evolving. T cells have remarkably varied effector functions including protecting the host from infection, activating cells of the innate immune system, releasing cytokines and chemokines, and heavily contributing to immunological memory. Under healthy conditions, T cells orchestrate a finely tuned attack on invading pathogens while minimizing damage to the host. The dark side of T cells is that they also exhibit autoreactivity and inflict harm to host cells, creating autoimmunity. The mechanisms of T cell autoreactivity are complex and dynamic. Emerging research is elucidating the mechanisms leading T cells to become autoreactive and how such responses cause or contribute to diverse disease states, both peripherally and within the central nervous system. This review provides foundational information on T cell development, differentiation, and functions. Key T cell subtypes, cytokines that create their effector roles, and sex differences are highlighted. Pathological T cell contributions to diverse peripheral and central disease states, arising from errors in reactivity, are highlighted, with a focus on multiple sclerosis, rheumatoid arthritis, osteoarthritis, neuropathic pain, and type 1 diabetes.

Toll-like receptor 2 and 4 antagonism for the treatment of experimental autoimmune encephalomyelitis (EAE)-related pain.

Neuropathic pain is a major symptom of multiple sclerosis (MS) with up to 92% of patients reporting bodily pain, and 85% reporting pain severe enough to cause functional disability. None of the available therapeutics target MS pain. Toll-like receptors 2 and 4 (TLR2/TLR4) have emerged as targets for treating a wide array of autoimmune disorders, including MS, as well as having demonstrated success at suppressing pain in diverse animal models. The current series of studies tested systemic TLR2/TLR4 antagonists in males and females in a low-dose Myelin oligodendrocyte glycoprotein (MOG) experimental autoimmune encephalomyelitis (EAE) model, with reduced motor dysfunction to allow unconfounded testing of allodynia through 50+ days post-MOG. The data demonstrated that blocking TLR2/TLR4 suppressed EAE-related pain, equally in males and females; upregulation of dorsal spinal cord proinflammatory gene expression for TLR2, TLR4, NLRP3, interleukin-1ß, IkBα, TNF-α and interleukin-17; and upregulation of dorsal spinal cord expression of glial immunoreactivity markers. In support of these results, intrathecal interleukin-1 receptor antagonist reversed EAE-induced allodynia, both early and late after EAE induction. In contrast, blocking TLR2/TLR4 did not suppress EAE-induced motor disturbances induced by a higher MOG dose. These data suggest that blocking TLR2/TLR4 prevents the production of proinflammatory factors involved in low dose EAE pathology. Moreover, in this EAE model, TLR2/TLR4 antagonists were highly effective in reducing pain, whereas motor impairment, as seen in high dose MOG EAE, is not affected.

Experimental autoimmune encephalopathy (EAE)-induced hippocampal neuroinflammation and memory deficits are prevented with the non-opioid TLR2/TLR4 antagonist (+)-naltrexone.

Multiple sclerosis (MS) is associated with burdensome memory impairments and preclinical literature suggests that these impairments are linked to neuroinflammation. Previously, we have shown that toll-like receptor 4 (TLR4) antagonists, such as (+)-naltrexone [(+)-NTX], block neuropathic pain and associated spinal inflammation in rats. Here we extend these findings to first demonstrate that (+)-NTX blocks TLR2 in addition to TLR4. Additionally, we examined in two rat strains whether (+)-NTX could attenuate learning and memory disturbances and associated neuroinflammation using a low-dose experimental autoimmune encephalomyelitis (EAE) model of MS. EAE is the most commonly used experimental model for the human inflammatory demyelinating disease, MS. This low-dose model avoided motor impairments that would confound learning and memory measurements. Fourteen days later, daily subcutaneous (+)-NTX or saline injections began and continued throughout the study. Contextual and auditory-fear conditioning were conducted at day 21 to assess hippocampal and amygdalar function. With this low-dose model, EAE impaired long-term, but not short-term, contextual fear memory; both long-term and short-term auditory-cued fear memory were spared. This was associated with increased mRNA for hippocampal interleukin-1ß (IL-1ß), TLR2, TLR4, NLRP3, and IL-17 and elevated expression of the microglial marker Iba1 in CA1 and DG regions of the hippocampus, confirming the neuroinflammation observed in higher-dose EAE models. Importantly, (+)-NTX completely prevented the EAE-induced memory impairments and robustly attenuated the associated proinflammatory effects. These findings suggest that (+)-NTX may exert therapeutic effects on memory function by dampening the neuroinflammatory response in the hippocampus through blockade of TLR2/TLR4. This study suggests that TLR2 and TLR4 antagonists may be effective at treating MS-related memory deficits.