No abstract

Prior work has shown that a high dose (20mg/kg) of systemic morphine, required to produce significant analgesia in the acute phase of a contusion injury, undermines the long-term health of treated subjects and increases lesion size. Moreover, a single dose of systemic morphine in the early stage of injury (24 h post-injury) led to symptoms of neuropathic pain 3 weeks later, in the chronic phase. The present study examines the locus of the effects using intrathecal morphine administration. Subjects were treated with one of three doses (0, 30, or 90 µg) of intrathecal morphine 24 h after a moderate contusion injury. The 90-µg dose produced significant analgesia when subjects were exposed to noxious stimuli (thermal and incremented shock) below the level of injury. Yet, despite analgesic efficacy, intrathecal morphine significantly attenuated the recovery of locomotor function and increased lesion size rostral to the injury site. A single dose of 30 or 90 µg of intrathecal morphine also decreased weight gain, and more than doubled the incidence of mortality and autophagia when compared to vehicle-treated controls. Morphine is one of the most effective pharmacological agents for the treatment of neuropathic pain and, therefore, is indispensable for the spinally injured. Treatment can, however, adversely affect the recovery process. A morphine-induced attenuation of recovery may result from increases in immune cell activation and, subsequently, pro-inflammatory cytokine concentrations in the contused spinal cord.

Significantly extended life expectancy coupled with contemporary sedentary lifestyles and poor nutrition have created a global epidemic of cardiovascular disease and stroke. For women, this issue is complicated by the discrepant outcomes of hormone therapy (HT) for stroke incidence and severity as well as the therapeutic complications for stroke associated with advancing age. Here we propose that the impact of estrogen therapy cannot be considered in isolation, but should include age-related changes in endocrine, immune, and nucleic acid mediators that collaborate with estrogen to produce neuroprotective effects commonly seen in younger, healthier demographics. Due to their role as modulators of ischemic cell death, the post-stroke inflammatory response, and neuronal survival and regeneration, this review proposes that Insulin-like Growth Factor (IGF)-1, Vitamin D, and discrete members of the family of non-coding RNA peptides called microRNAs (miRNAs) may be crucial biochemical markers that help determine the neuroprotective “window” of HT. Specifically, IGF-1 confers neuroprotection in concert with, and independently of, estrogen and failure of the insulin/IGF-1 axis is associated with metabolic disturbances that increase the risk for stroke. Vitamin D and miRNAs regulate and complement IGF-1 mediated function and neuroprotective efficacy via modulation of IGF-1 availability and neural stem cell and immune cell proliferation, differentiaton and secretions. Together, age-related decline of these factors differentially affects stroke risk, severity, and outcome, and may provide a novel therapeutic adjunct to traditional HT practices.

No abstract

Stroke is the third leading cause of death worldwide, and Vitamin D deficiency is associated with increased stroke risk, severity, and mortality. Vitamin D potently regulates the immune system and the post-stroke inflammatory response plays a critical role in ischemia-induced CNS pathogenesis; and neuroimmune interactions in the CNS and periphery regulate the nature, extent, and duration of inflammation. Previous studies from this lab indicate that Vitamin D deficiency (VDD) exacerbates ischemic cell loss and sensory motor behavioral deficits in adult rats subject to middle cerebral artery occlusion, an experimental stroke model. Changes in inflammatory cytokines post-ischemia included increased TGF-β expression in both groups but significantly higher IL-6 expression in VDD ischemic cortical tissues than control levels. Increased IL-6 levels in the presence of TGF-β is known to induce pathogenic CD4+ Th17 cell development and suppress neuroprotective Treg generation. In the present studies we used flow cytometry to examine Th17 and Treg subsets in ischemic cortical and splenic tissues. Flow cytometry indicated that VDD rats had significantly less activated Treg cells in ischemic cortical and splenic tissue, while Th17 activation was significantly increased in VDD ischemic cortical tissue. Due to the dysregulation of Treg:Th17 subsets in VDD animals post-stroke and the recently recognized role of the spleen and peripheral nervous system in ischemia-associated neurodegeneration we hypothesized that adoptive transfer of CD4+ T cells harvested from the spleen of control animals 2d post-stroke to the VDD group acutely following middle cerebral artery occlusion (4h) may provide key neuroimmune regulatory elements and/or neuroprotective immune cells and secretions. We found that splenic CD4+ adoptive transfer to VDD rats 4h post-stroke markedly improved infarct volume, survival, and behavioral performance as compared with VDD animals injected with vehicle alone. Together, these results suggest that peripheral immune status significantly influences stroke severity and that acute manipulation of the peripheral immune system post-stroke can prevent or ameliorate inflammation-associated neurodegeneration.

Vitamin D deficiency is widespread and considered a risk factor for cardiovascular disease and events such as stroke, and low Vitamin D (VD) levels are predictive for stroke and more fatal strokes in humans. VD’s ability to act as a selective endocrine and immunomodulator suggests a role for this hormone in reducing stroke-induced inflammation in the brain. However, the specific contribution of Vitamin D deficiency to stroke is not clear since it occurs with other co-morbid conditions, such as type 2 diabetes and obesity, which are also risk factors for cerebrovascular disease. To directly assess the impact of VD deficiency on stroke severity, adult female rats were fed control or VD deficient (VDD) diet for 6 weeks. The VDD diet reduced circulating VD levels to 25% of controls (p<0.05). Control and VDD groups were then subject to ischemic stroke by vasoconstriction of the Middle Cerebral Artery (MCA) by endothelin-1. Both groups displayed cortical and striatal infarction, however, infarct volumes were significantly larger in the VDD group in both the cortex (20%) and striatum (50%), when measured 5d post stroke. Furthermore, sensory motor function was more severely impaired in the VDD group, as measured by the tape test and the vibrissae evoked forelimb placement task (p<0.05). In the ischemic brain, IGF-1, which is a neuroprotective peptide hormone, is routinely elevated and the elevation was attenuated in the VDD groups (p<0.05). Additionally, VDD significantly reduced IL-1α, IL-1β, IL-2, IL-4, IFN-γ, and IL-10 expression in ischemic brain tissue, but elevated ischemia-induced IL-6. IL-6 was positively correlated with infarct volume (r2=.83 cortex, r2=.90 striatum) (p<.05). IL-6 promotes development and expansion of the Th17 cohort, whose cytokines secretions are a key factor in blood brain barrier disruption after stroke. These data support the hypothesis that VD deficiency independently modulates stroke severity by disrupting the expression of normally neuroprotective compounds (IGF-1) and elevating cytotoxic proteins (IL-6) in the ischemic brain. Supported by NIH AG027684 and AG028303 to FS.