Osteoarthritis (OA), a degenerative joint disease, is associated with increased systemic inflammation, chronic pain, and cardiovascular dysfunction. Epidemiological evidence establishes that OA increases the risk of cardiovascular disease (CVD) threefold, yet the causal role of OA's contributions remains underexamined. We assessed cardiac function longitudinally following destabilization of the medial meniscus (DMM) surgery to induce osteoarthritis in mice. DMM-mice exhibited significant, sexually dimorphic alterations in echocardiographic parameters. Female DMM mice developed impaired relaxation with altered E/A ratios, increased E/e' ratios, and prolonged intraventricular relaxation time with no change in ejection fraction, while male DMM mice showed progressive systolic dysfunction with decreasing ejection fraction, increased E/e' ratio, and prolonged intraventricular contraction time. Transcriptomic profiles and biochemical analyses demonstrated divergent cellular responses involving fibrosis and oxidative stress in female mice, whereas autophagic and apoptotic responses were observed in male mice. Using a tumor necrosis factor 2 (TNFR2) agonist shown to reduce systemic inflammation, we investigated its potential therapeutic role in the context of OA-induced cardiovascular dysfunction. TNFR2 agonism proved to be effective both prophylactically and therapeutically for female diastolic dysfunction. While prophylactic and therapeutic administration delayed male systolic dysfunction, the efficacy declined over time. Our findings demonstrate evidence of a novel sexually dimorphic model of OA-induced CVD that recapitulates the sexually dimorphic pattern of patient phenotypes and a promising new therapeutic approach to CVD.

Multiple sclerosis (MS) is an autoimmune neurodegenerative disorder with approximately 80 % of patients suffering from pain and 50 % from paralysis. Using a rodent model for MS, experimental autoimmune encephalomyelitis (EAE), researchers have predominately investigated paralysis/motor disease as the clinical symptom of EAE with fewer studying MS/EAE pain. However, in EAE, all mice exhibit a pain like phenotype and only a subset progresses to paralysis. Despite extensive research characterizing the disease pathology, the etiology that contributes to the range of pain and motor symptom occurrence in MS remains understudied. This is the first study to dissect MS symptom pathophysiology, using the non-PTX EAE model, in mice that experience mechanical hypersensitivity (pain-like phenotype) with and without paralysis. We found that mechanical hypersensitivity experienced by mice with or without paralysis is comparable between the two groups, irrespective of sex. In addition, there is a significant increase in the activation and infiltration of immune cells, demyelination, and heightened protein expression of B cell chemoattractant CXCL13 within the spinal cord of mice exhibiting mechanical hypersensitivity and paralysis, compared to mice only experiencing mechanical hypersensitivity.

After high-level spinal cord injury (SCI), persistently reactive microglia drive widespread plasticity throughout the neuraxis. Plasticity in the thoracolumbar cord, a region corresponding to the spinal sympathetic reflex (SSR) circuit, contributes to the development of sympathetic dysfunction and associated immune disorders. The transcription factor NF-κB is activated after SCI, promoting a pro-inflammatory loop by driving the expression of inflammatory mediators which further activate NF-κB signaling. We hypothesize that microglial NF-κB signaling via IKKβ modulates microglial activity, impacting central and peripheral immune activity related to the SSR circuit post-SCI. We assessed the effect of deleting canonical IKKβ in CNS-resident microglia, its impact on microglial activation, polarization, central transcriptional activity, and peripheral immune activity at 1- and 4-week post-SCI (wpi). Transcriptomic analyses reveal microglial IKKβ influences immune-related pathways in the thoracolumbar cord at 1 wpi. We show that inhibition of microglial NF-κB signaling via deletion of the activator IKKβ mitigates injury-induced increases in "proinflammatory" M1 microglia in the thoracolumbar cord at 4 wpi and increases the quantity of splenocytes at 1 wpi. This study advances our understanding of how microglial IKKβ signaling shapes the neuroimmune response and a peripheral immune organ after SCI.

OBJECTIVE:This review aims to assess the existing evidence that connects osteoarthritis (OA) with neurodegenerative diseases, specifically Alzheimer's disease (AD) and Parkinson's disease (PD), and to elucidate shared mechanisms that may contribute to the development of innovative therapeutic approaches. METHOD:We present a narrative review of prior epidemiological, genetic, and mechanistic studies that describe overlapping risk factors and convergent pathological pathways linking OA and neurodegenerative diseases. Key focus areas include metabolic and hormonal influences, inflammatory cytokine signaling, and mitochondrial dysfunction that arise in both OA and neurodegenerative diseases. RESULTS:Emerging evidence indicates that OA and neurodegenerative diseases share core drivers-advanced age, obesity, metabolic syndrome, and genetic susceptibility. Central to both are chronic inflammation, mediated by tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β), as well as mitochondrial dysfunction, which promote both cartilage degradation and neuronal death. Genetic data reveal consistent activation of NF-κB and JAK/STAT signaling, with contributions from MAPK, TGF-β, and WNT signaling pathways. Preclinical models demonstrate that OA-induced peripheral inflammation can amplify neuroinflammation and accelerate AD-like pathology, underscoring a potential bidirectional link. Despite these associations, causal relationships have not been concretely established. CONCLUSION:OA may contribute to neurodegenerative risk through shared inflammatory and metabolic mechanisms, representing an underrecognized intersection between musculoskeletal and neurological diseases. Targeting these convergent pathways offers a promising avenue for dual-purpose interventions. Establishing causality through longitudinal and mechanistic studies could enable early identification of at-risk patients and guide the development of therapies that mitigate both joint degeneration and neurodegeneration.

Heightened sympathetic reflexes (sympathetic hyperreflexia, SH) post-high-level spinal cord injury (SCI) detrimentally impact effector organs, resulting in peripheral immune dysfunction and cardiovascular disease, two leading causes of morbidity and mortality in SCI. We previously found that an activated neuroimmune system after SCI contributes to intraspinal plasticity in the spinal sympathetic reflex (SSR) circuit, underlying SH. We hypothesize that activation of NF-κB, a key regulator of inflammation, in spinal cord below-SCI contributes to driving SSR circuit plasticity, resulting in SH-associated autonomic dysreflexia (AD) and peripheral immune dysfunction. Here, we demonstrate inhibition of central NF-κB signaling via intrathecal delivery of dimethylamino parthenolide (DMAPT) significantly decreases SH post-complete transection of thoracic spinal segment 3 in adult rats. This included reduced AD severity that was associated with decreased interneuron recruitment into the SSR circuit after SCI. We also observed intrathecal DMAPT-treatment improved survival post-SCI that corresponded with normalized numbers of splenic regulatory T-cells. These findings underscore central NF-κB signaling as a key component driving SH after SCI.

Spinal cord injury (SCI) is a devastating condition with 250,000 to 500,000 new cases globally each year. Respiratory infections, e.g., pneumonia and influenza are the leading cause of death after SCI. Unfortunately, there is a poor understanding of how altered neuro-immune communication impacts an individual's outcome to infection. In humans and rodents, SCI leads to maladaptive changes in the spinal-sympathetic reflex (SSR) circuit which is crucial to sympathetic function. The cause of the impaired immune function may be related to harmful neuroinflammation which is detrimental to homeostatic neuronal function, aberrant plasticity, and hyperexcitable circuits. Soluble tumor necrosis factor (sTNF) is a pro-inflammatory cytokine that is elevated in the CNS after SCI and remains elevated for several months after injury. By pharmacologically attenuating sTNF in the CNS after SCI we were able to demonstrate improved immune function. Furthermore, when we investigated the specific cellular population which may be involved in altered neuro-immune communication we reported that excessive TNFR1 activity on excitatory INs promotes immune dysfunction. Furthermore, this observation is NF-kβ dependent in VGluT2 + INs. Our data is the first report of a target within the CNS, TNFR1, that contributes to SCI-induced immune dysfunction after T9-SCI and is a potential avenue for future therapeutics.

Chronic morbidities, including cognitive impairment, are a common consequence of traumatic brain injury (TBI), with millions currently living with permanent TBI-related disabilities. Recent work has indicated that altered cellular architecture in the dentate gyrus (DG) may play a significant role in the development of chronic cognitive impairment and excitotoxicity. However, current understanding of the temporal progression of these pathological changes in the context of neuroinflammation and chronic cognitive outcomes is limited. This study characterized temporospatial changes in the hilar region of the DG, showing that the population of reelin- and somatostatin-expressing inhibitory interneurons was significantly reduced as early as 7 days post-injury (dpi), and that aberrant migration of excitatory granule cells occurs gradually in the weeks to months following injury. These findings coincided with upregulation of monocyte/macrophage-associated inflammatory mediators, including MIP-1β, MIG, MCP-1, and TNF-α at 7 days dpi, with differential cytokine regulation persisting 120 dpi. Injury was associated with the development of chronic spatial memory impairment and reduced risk-assessment behavior, with a transient reduction in spontaneous anxiety. TNFR1 and TNFR2 were differentially expressed in inhibitory neurons, further implicating TNF-signaling as a driver of hilar neuron loss. Furthermore, systemic administration of anti-TNF-α monoclonal antibody induced significant neuroprotection, attenuated pro-inflammatory mediators, and hilar interneuron loss. These findings suggest that TNF-TNFR signaling plays a crucial role in driving hilar interneuron loss and aberrant granule cell migration, which, in turn, may contribute to the development of excitotoxicity and chronic cognitive deficits.

Tumor necrosis factor receptor 2 (TNFR2) activation is a promising-therapeutic strategy for autoimmune disorders such as multiple sclerosis (MS) and chronic neuropathic pain (CNP). This study aimed to identify mechanisms governing the sex-specific efficacy of TNFR2 activation on abrogating pain and motor disease severity in mice experiencing experimental autoimmune encephalomyelitis (EAE), a rodent model of MS. We find that the XX sex-chromosome complement is indispensable for TNFR2-mediated attenuation of EAE-associated motor disease. Mice with XY chromosomes experienced exacerbated motor disease severity, associated with an elevated magnitude of neurodegeneration and demyelination. Contrasting this, we show that TNFR2-mediated alleviation of EAE induced CNP is both sex and sex-chromosome independent. However, the alleviation of CNP following TNFR2 activation across two different neuropathic pain models (EAE and chronic constriction injury) was dependent on the gonadal hormone Activin-A. This suggests a shared mechanism through which gonadal-derived factors impact TNFR2-mediated pain relief, independent of sex hormones. These findings highlight the importance of considering sex chromosomes and sex-independent gonadal hormones in evaluating potential sex-specific differences in drug efficacy during therapeutic development.

Multiple sclerosis (MS), a demyelinating autoimmune disease of the central nervous system (CNS), predominately affects females compared to males. Tumor necrosis factor (TNF), a pro-inflammatory cytokine, signaling through TNF receptor 1 contributes to inflammatory disease pathogenesis. In contrast, TNF receptor 2 signaling is neuroprotective. Current anti-TNF MS therapies are shown to be detrimental to patients due to pleiotropic effects on both pro- and anti-inflammatory functions. Using a non-pertussis toxin (nPTX) experimental autoimmune encephalomyelitis (EAE) model in C57BL/6 mice, we systemically administered a TNFR2 agonist (p53-sc-mTNFR2) to investigate behavioral and pathophysiological changes in both female and male mice. Our data shows that TNFR2 activation alleviates motor and sensory symptoms in females. However, in males, the agonist only alleviates sensory symptoms and not motor. nPTX EAE induction in TNFR2 global knockout mice caused exacerbated motor symptoms in females along with an earlier day of onset, but not in males. Our data demonstrates that TNFR2 agonist efficacy is sex-specific for alleviation of motor symptoms, however, it effectively reduces mechanical hypersensitivity in both females and males. Altogether, these data support the therapeutic promise TNFR2 agonism holds as an MS therapeutic and, more broadly, to treat central neuropathic pain.

ABSTRACT Upregulation of soluble tumor necrosis factor (sTNF) cytokine signaling through TNF receptor 1 (TNFR1) and subsequent neuronal hyperexcitability are observed in both animal models and human chronic neuropathic pain (CNP) (Clark et al., 2013; Empl et al., 2001; Ji et al., 2018; Lindenlaub and Sommer, 2003). To test the hypothesis that supraspinal circuitry is critical to pain chronification, we studied the intersect between supraspinal TNFR1 mediated neuronal signaling and sex specificity by selectively removing TNFR1 in Nex+ neurons in adult mice (NexCre ERT2 ::TNFR1 f/f ). We determined that following chronic constriction injury (CCI), pain resolves in males; however, female acute pain transitions to chronic. Subsequently, we investigated two downstream pathways, p38MAPK and NF-κB, important in TNFR1 signaling and injury response. We detected p38αMAPK and NF-κB activation in male cortical tissue; however, p38αMAPK phosphorylation was reduced in NexCre ERT2 ::TNFR1 f/f males. We observed similar behavioral results following CCI in NexCre ERT2 ::p38αMAPK f/f mice. Previously, we established estrogen’s ability to modulate sTNF/TNFR1 signaling in CNP, which may contribute to female prevalence of CNP (Bouhassira et al., 2008; Claiborne et al., 2006; de Mos et al., 2007; Del Rivero et al., 2019; Li et al., 2009). To explore the intersection between estrogen and inflammation in CNP we used a combination therapy of an estrogen receptor β (ER β) inhibitor with a sTNF/TNFR1 or general p38MAPK inhibitor. We determined both combination therapies lend “male-like” therapeutic relief to females following CCI. These data suggest that TNFR1/p38αMAPK signaling in Nex+ neurons in CNP is male-specific and lack of therapeutic efficacy following sTNF inhibition in females is due to ER β interference. These studies highlight sex-specific differences in pathways important to pain chronification and elucidate potential therapeutic strategies that would be effective in both sexes.

Postural control is critical for locomotion, allowing for gait changes, obstacle avoidance and navigation of rough terrain. A major problem after spinal cord injury (SCI) is regaining the control of balance to prevent falls and further injury. While the circuits for locomotor pattern generation reside in the spinal cord, postural control consists of multiple, complex networks that interact at the spinal, brainstem and cortical levels. After complete SCI, cortical reorganization establishes novel control of trunk musculature that is required for weight-supported stepping. In this study, we examined the impact of exercise therapy on cortical reorganization in the more clinically relevant models of both moderate and severe midthoracic contusion injury in the rat. Results demonstrate that both spontaneous recovery and therapy induced recovery of weight-supported stepping utilize cortical reorganization. Moreover, exercise therapy further improves outcome by enhancing cortical control of lower thoracic muscles enabling improvements in interlimb coordination associated with improved balance that increases weight-supported stepping. The outcome of this study suggest that cortical control of posture is key to functional improvement in locomotion. This information can be used to improve the timing and type of therapy after SCI by considering changes along the entire neural axis.

Activation of the endoplasmic reticulum (ER) stress sensor inositol‐requiring enzyme‐1α (IRE1α) contributes to neuronal development and is known to induce neuronal remodeling in vitro and in vivo. On the contrary, excessive IRE1 activity is often detrimental and may contribute to neurodegeneration. To determine the consequences of increased activation of IRE1α, we used a mouse model expressing a C148S variant of IRE1α with increased and sustained activation. Surprisingly, the mutation did not affect the differentiation of highly secretory antibody‐producing cells but exhibited a beneficial effect in a mouse model of experimental autoimmune encephalomyelitis (EAE). Although mechanical allodynia was unaffected, significant improvement in motor function was found in IRE1C148S mice with EAE relative to wild type (WT) mice. Coincident with this improvement, there was reduced microgliosis in the spinal cord of IRE1C148S mice, with reduced expression of proinflammatory cytokine genes. This was accompanied by reduced axonal degeneration and enhanced 2',3'‐cyclic nucleotide 3'‐phosphodiesterase (CNPase) levels, suggesting improved myelin integrity. Interestingly, while the IRE1C148S mutation is expressed in all cells, the reduction in proinflammatory cytokines and in the microglial activation marker ionized calcium‐binding adapter molecule (IBA1), along with preservation of phagocytic gene expression, all point to microglia as the cell type contributing to the clinical improvement in IRE1C148S animals. Our data suggest that sustained increase in IRE1α activity can be beneficial in vivo, and that this protection is cell type and context dependent. Considering the overwhelming but conflicting evidence for the role of ER stress in neurological diseases, a better understanding of the function of ER stress sensors in physiological contexts is clearly needed.

Activation of the ER stress sensor IRE1α contributes to neuronal development and is known to induce neuronal remodeling in vitro and in vivo. On the other hand, excessive IRE1 activity is often detrimental and may contribute to neurodegeneration. To determine the consequences of increased activation of IRE1α, we used a mouse model expressing a C148S variant of IRE1α with increased and sustained activation. Surprisingly, the mutation did not affect the differentiation of highly secretory antibody-producing cells, but exhibited a strong protective effect in a mouse model of experimental autoimmune encephalomyelitis (EAE). Significant improvement in motor function was found in IRE1C148S mice with EAE relative to WT mice. Coincident with this improvement, there was reduced microgliosis in the spinal cord of IRE1C148S mice, with reduced expression of pro-inflammatory cytokine genes. This was accompanied by reduced axonal degeneration and enhanced CNPase levels, suggestiing improved myelin integrity. Interestingly, while the IRE1C148S mutation is expressed in all cells, the reduction in proinflammatory cytokines and in the activation of microglial activation marker IBA1, along with preservation of phagocytic gene expression, all point to microglia as the cell type contributing to the clinical improvement in IRE1C148S animals. Our data suggest that sustained increase in IRE1α activity can be protective in vivo, and that this protection is cell type and context dependent. Considering the overwhelming but conflicting evidence for the role of the ER stress in neurological diseases, a better understanding of the function of ER stress sensors in physiological contexts is clearly needed.

Loss of function in transport protein particles (TRAPP) links a new set of emerging genetic disorders called "TRAPPopathies". One such disorder is NIBP syndrome, characterized by microcephaly and intellectual disability, and caused by mutations of NIBP/TRAPPC9, a crucial and unique member of TRAPPII. To investigate the neural cellular/molecular mechanisms underlying microcephaly, we developed Nibp/Trappc9-deficient animal models using different techniques, including morpholino knockdown and CRISPR/Cas mutation in zebrafish and Cre/LoxP-mediated gene targeting in mice. Nibp/Trappc9 deficiency impaired the stability of the TRAPPII complex at actin filaments and microtubules of neurites and growth cones. This deficiency also impaired elongation and branching of neuronal dendrites and axons, without significant effects on neurite initiation or neural cell number/types in embryonic and adult brains. The positive correlation of TRAPPII stability and neurite elongation/branching suggests a potential role for TRAPPII in regulating neurite morphology. These results provide novel genetic/molecular evidence to define patients with a type of non-syndromic autosomal recessive intellectual disability and highlight the importance of developing therapeutic approaches targeting the TRAPPII complex to cure TRAPPopathies.

Spinal cord injury (SCI) is a devastating condition with 250,000 to 500,000 new cases globally each year. Respiratory infections, e.g., pneumonia and influenza, are the leading cause of death after SCI. For instance, an individual with SCI is 37 times more likely to become infected and hospitalized from the flu. Yet, the field has a poor understanding of how immune dysfunction arises after trauma to the central nervous system (CNS) and how altered neuro-immune communication impacts an individual’s outcome to infection. In humans and rodents, SCI leads to maladaptive changes in the spinal-sympathetic reflex (SSR) circuit which is crucial to sympathetic function. Soluble Tumor Necrosis Factor (sTNF) is a pro-inflammatory cytokine that is elevated in the CNS after SCI and remains elevated for several months after injury. We recently demonstrated that blocking TNFR1 activation in the CNS, using XPro1595, decreased the maladaptive excitability of SpINs in the SSR circuit leading to improved immune response to infection after SCI. We hypothesize that hyper-excitability of glutamatergic SpINs after SCI due to persistent TNFR1 activation contributes to immune dysfunction. To test this, we utilized viral mediated targeted knock-down of TNFR1 on excitatory SpINs, and demonstrated that inhibiting TNFR1 on excitatory interneurons contributes to improved immune function, including an increase in virus-specific T cells and decrease in viral load remaining in the lung after infection. Supported by grants from NIH (R01 NS111761) Supported by grants from NIH (R01 NS111761)

After a severe, high-level spinal cord injury (SCI), plasticity to intraspinal circuits below injury results in heightened spinal sympathetic reflex activity and detrimentally impacts peripheral organ systems. Such sympathetic hyperreflexia is immediately apparent as an episode of autonomic dysreflexia (AD), a life-threatening condition characterized by sudden hypertension and reflexive bradycardia following below-level sensory inputs; for example, pressure sores or impacted fecal matter. Over time, plasticity within the spinal sympathetic reflex (SSR) circuit contributes to the progressive intensification of AD events, as the frequency and severity of AD events increase greatly beginning ∼2 weeks post-injury (wpi). The neuroimmune system has been implicated in driving sympathetic hyperreflexia, as inhibition of the cytokine soluble tumor necrosis factor-alpha (sTNFα) using the biological mimetic XPro1595 beginning within days post-SCI has been shown to attenuate the development of AD. Here, we sought to further understand the effective therapeutic time window of XPro1595 to diminish sympathetic hyperreflexia, as indicated by AD. We delayed the commencement of continuous intrathecal administration of XPro1595 until 2 weeks after a complete, thoracic level 3 injury in adult rats. We examined the severity of colorectal distension-induced AD biweekly. We found that initiation of sTNFα inhibition at 2 wpi does not attenuate the severity or intensification of sympathetic hyperreflexia compared with saline-treated controls. Coupled with previous data from our group, these findings suggest that central sTNFα signaling must be targeted prior to 2 weeks post-SCI in order to decrease sympathetic hyperreflexia.

Multiple Sclerosis (MS) is a debilitating autoimmune disease often accompanied by severe chronic pain. The most common type of pain in MS, called neuropathic pain, arises from disease processes affecting the peripheral and central nervous systems. It is incredibly difficult to study these processes in patients, so animal models such as experimental autoimmune encephalomyelitis (EAE) mice are used to dissect the complex mechanisms of neuropathic pain in MS. The pleiotropic cytokine tumor necrosis factor α (TNFα) is a critical factor mediating neuropathic pain identified by these animal studies. The TNF signaling pathway is complex, and can lead to cell death, inflammation, or survival. In complex diseases such as MS, signaling through the TNFR1 receptor tends to be pro-inflammation and death, whereas signaling through the TNFR2 receptor is pro-homeostatic. However, most TNFα-targeted therapies indiscriminately block both arms of the pathway, and thus are not therapeutic in MS. This review explores pain in MS, inflammatory TNF signaling, the link between the two, and how it could be exploited to develop more effective TNFα-targeting pain therapies.