Estradiol Treatment Prevents Injury Induced Enhancement in Spinal Cord Dynorphin Expression

Abstract

Administration of the ovarian steroid estradiol in male and female animals has been shown to have neuromodulatory and neuroprotective effects in a variety of experimental models. In the present study, spinal tissues from dermatomes just above (T5–T7, at level) a severe chronic spinal cord injury (SCI) at T8 were analyzed for expression levels of prodynorphin (PRDN) and phospho-(serine 369) κ-opioid receptor (KOR-P) in 17 β estradiol (EB)- and placebo-treated adult male rats. Dynorphin was targeted since (1) it has previously been shown to be elevated post-SCI, (2) intrathecal injection of dynorphin produces several of the same adverse effects seen with a SCI, and (3) its increased expression is known to occur in a variety of different experimental models of central neuropathic pain. A significant elevation of extracellular levels of both PRDN and KOR-P in the placebo-treated SCI group relative to uninjured surgical sham controls was found in spinal tissues above the injury level, indicating increased dynorphin levels. Importantly, the EB-treated SCI group did not show elevations of PRDN levels at 6 weeks post-injury. Immunohistochemical analysis of at level tissues revealed that EB treatment significantly prevented a post-SCI increase in expression of PRDN puncta co-labeling synapsin I, a nerve terminal marker. The dynorphin-containing terminals co-labeled vesicular glutamate receptor-2 (a marker of glutamatergic terminals), a finding consistent with a non-opioid basis for the adverse effects of dynorphin. These results support a beneficial role for EB treatment post-SCI through a reduction in excessive spinal cord levels of dynorphin. Studies manipulating the timing of the EB treatment post-injury along with specific functional assessments will address whether the beneficial effects are due to EB’s potential neuromodulatory or neuroprotective action.

Effects of exercise training on urinary tract function after spinal cord injury

“…All the samples were run at least three times, and the bands from all the tests were analyzed by inverse densitometry using ImageJ 1.47 (version 1.47, National Institutes of Health) according to our previous protocols (40). Each individual value was normalized by subtracting the background and dividing the value with corresponding ␤-actin values (minus background).…”

“…Expressions of the proteins TGF-␤ and CD11b were analyzed with Western blotting following our previously published protocols (40). The left kidney was sectioned (to include both cortex and medulla in the sample) on an ice tray and homogenized in ice-cold lysis buffer [50 mM Tris·HCl (pH 8.0), 200 mM NaCl, 50 mM NaF, 0.3% Triton X-100, 1 M DTT, 1 M benzamidine, 100 mM Na-orthovanadate, 100 mM PMSF] and protease inhibitor (78425, Halt protease inhibitor single-use cocktail, Thermo Scientific).…”

Changes in bone Pb accumulation: Cause and effect of altered bone turnover

“…This is consistent with the observation that, at 9 months post-OVX, OVX animals had already lower, although non-significant, mineral apposition rates than controls [37]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Moreover, in what concerns the lack of statistical significance of the EST induced decrease in bone turnover markers observed in this work in comparison with normal rats, it is first noted that 17-estradiol has been administered as an antiresorptive agent usually in ovariectomized rats [29], not on intact animals exposed to Pb, and at much higher dosing regimens than that used in this study [26,27,28]. Conceivably, Pb exposure combined with a low-dose, slow-release EST regimen administered to normal rats, may moderate the expected decrease in bone turnover markers induced by EST administered in the abovementioned standard conditions, and thus, result in a non significant change.…”

“…In the EST group, animals were given subcutaneous implants of 17-estradiol pellets (90-day release, 0.025 mg/pellet IRA), via a small incision in the skin of the neck just behind the right ear under brief isofluorane anesthesia. In view of published data, this slow-release dosing regimen is deemed to result in a 10 to 30% increase of physiological plasma estradiol levels in intact female and male Wistar rats [26,27,28]. All animals were fed the same diet, adequately for daily requirements but not ad lib in order to avoid obesity.…”

Challenges and opportunities of sensory plasticity after SCI

“…The effect of SCI on primary sensory neurons is an emerging topic of investigation (Huang et al, 2006; Shortland et al, 2006; Ramer et al, 2012; Walters, 2012) as a possible mechanism of SCI-related pain and other pathologies such as AD (e.g., Widerstrom-Noga et al, 2004). New approaches to applying knowledge of nociceptive mechanisms are also being tested as potential treatments for SCI-related sensory pathologies (Gupta and Hubscher, 2012; Lee et al, 2012; Rabchevsky et al, 2012; Ramer et al, 2012). …”