Thiazolidinediones (TZDs) are synthetic agonists of the ligand-activated transcription factor peroxisome proliferatoractivated receptor-c (PPARc). TZDs are known to curtail inflammation associated with peripheral organ ischemia. As inflammation precipitates the neuronal death after stroke, we tested the efficacy of TZDs in preventing brain damage following transient middle cerebral artery occlusion (MCAO) in adult rodents. As hypertension and diabetes complicate the stroke outcome, we also evaluated the efficacy of TZDs in hypertensive rats and type-2 diabetic mice subjected to transient MCAO. Pre-treatment as well as post-treatment with TZDs rosiglitazone and pioglitazone significantly decreased the infarct volume and neurological deficits in normotensive, normoglycemic, hypertensive and hyperglycemic rodents. Rosiglitazone neuroprotection was not enhanced by retinoic acid · receptor agonist 9-cis-retinoic acid, but was prevented by PPARc antagonist GW9662. Rosiglitazone significantly decreased the postischemic intercellular adhesion molecule-1 expression and extravasation of macrophages and neutrophils into brain. Rosiglitazone treatment curtailed the post-ischemic expression of the pro-inflammatory genes interleukin-1b, interleukin-6, macrophage inflammatory protein-1a, monocyte chemoattractant protein-1, cyclooxygenase-2, inducible nitric oxide synthase, early growth response-1, CCAAT/enhancer binding protein-b and nuclear factor-kappa B, and increased the expression of the anti-oxidant enzymes catalase and copper/zinc-superoxide dismutase. Rosiglitazone also increased the expression of the anti-inflammatory gene

Spinal injury disrupts connections between the brain and spinal cord, causing life-long paralysis. Most spinal injuries are incomplete, leaving spared neural pathways to motor neurons that initiate and coordinate movement. One therapeutic strategy to induce functional motor recovery is to harness plasticity in these spared neural pathways. Chronic intermittent hypoxia (CIH) (72 episodes per night, 7 nights) increases synaptic strength in crossed spinal synaptic pathways to phrenic motoneurons below a C2 spinal hemisection. However, CIH also causes morbidity (e.g., high blood pressure, hippocampal apoptosis), rendering it unsuitable as a therapeutic approach to chronic spinal injury. Less severe protocols of repetitive acute intermittent hypoxia may elicit plasticity without associated morbidity. Here we demonstrate that daily acute intermittent hypoxia (dAIH; 10 episodes per day, 7 d) induces motor plasticity in respiratory and nonrespiratory motor behaviors without evidence for associated morbidity. dAIH induces plasticity in spared, spinal pathways to respiratory and nonrespiratory motor neurons, improving respiratory and nonrespiratory (forelimb) motor function in rats with chronic cervical injuries. Functional improvements were persistent and were mirrored by neurochemical changes in proteins that contribute to respiratory motor plasticity after intermittent hypoxia (BDNF and TrkB) within both respiratory and nonrespiratory motor nuclei. Collectively, these studies demonstrate that repetitive acute intermittent hypoxia may be an effective and non-invasive means of improving function in multiple motor systems after chronic spinal injury.

Thiazolidinediones (TZDs) are potent synthetic agonists of the ligand-activated transcription factor peroxisome proliferatoractivated receptor-␥ (PPAR␥). TZDs were shown to induce neuroprotection after cerebral ischemia by blocking inflammation. As spinal cord injury (SCI) induces massive inflammation that precipitates secondary neuronal death, we currently analyzed the therapeutic efficacy of TZDs pioglitazone and rosiglitazone after SCI in adult rats. Both pioglitazone and rosiglitazone (1.5 mg/kg i.p.; four doses at 5 min and 12, 24, and 48 h) significantly decreased the lesion size (by 57 to 68%, p Ͻ 0.05), motor neuron loss (by 3-to 10-fold, p Ͻ 0.05), myelin loss (by 66 to 75%, p Ͻ 0.05), astrogliosis (by 46 to 61%, p Ͻ 0.05), and microglial activation (by 59 to 78%, p Ͻ 0.05) after SCI. TZDs significantly enhanced the motor function recovery (at 7 days after SCI, the motor scores were 37 to 45% higher in the TZD groups over the vehicle group; p Ͻ 0.05), but the treatment was effective only when the first injection was given by 2 h after SCI. At 28 days after SCI, chronic thermal hyperalgesia was decreased significantly (by 31 to 39%; p Ͻ 0.05) in the pioglitazone group compared with the vehicle group. At 6 h after SCI, the pioglitazone group showed significantly less induction of inflammatory genes [interleukin (IL)-6 by 83%, IL-1␤ by 87%, monocyte chemoattractant protein-1 by 75%, intracellular adhesion molecule-1 by 84%, and early growth response-1 by 67%] compared with the vehicle group (p Ͻ 0.05 in all cases). Pioglitazone also significantly enhanced the post-SCI induction of neuroprotective heat shock proteins and antioxidant enzymes. Pretreatment with a PPAR␥ antagonist, 2-chloro-5-nitro-N-phenyl-benzamide (GW9662), prevented the neuroprotection induced by pioglitazone.Peroxisome proliferator-activated receptor (PPAR) and retinoid X receptor are ligand-activated transcription factors of the nuclear hormone receptor superfamily. Upon ligand binding, PPAR forms a heterodimeric complex with retinoid X receptor that binds to the cis-acting sequences (peroxisome proliferator response element) on DNA to initiate or repress the transcription of target genes (Blanquart et al., 2003). PPAR exists as three isoforms (␣, ␥, and ␦/␤) that control many cellular functions including lipid metabolism, glucose absorption, and cell growth and differentiation (Escher and Wahli, 2000). 15-Deoxy-⌬-12,14-prostaglandin J 2 (15-d-PGJ 2 ) is the natural agonist and thiazolidinediones (TZDs) (troglitazone, ciglitazone, rosiglitazone, and pioglitazone) are potent synthetic agonists of PPAR␥. Of these, troglitazone was removed from the market because of hepatotoxicity, whereas rosiglitazone and pioglitazone are currently ap-

Increased levels of interleukin-6 (IL-6) play a role in post-ischemic cerebral inflammation. IL-6 binding to its receptors induces phosphorylation of the receptor associated janus kinases (JAKs), and the down-stream signal transducer and activator of transcription (STAT) family of transcription factors, which amplify the IL-6 signal transduction. We evaluated the functional significance of JAK2 and STAT3 activation in focal ischemia-induced neuronal damage. Transient middle cerebral artery occlusion in adult rats led to increased JAK2 and STAT3 phosphorylation in the ipsilateral cortex and striatum after 6-72 h of reperfusion. Fluorescent immunohistochemistry with cell specific markers (NeuN for neurons, glial fibrillary acidic protein for reactive astrocytes and ED1/OX42 for activated macrophages/microglia) showed that both pJAK2 and pSTAT3 staining is predominantly localized in the macrophages/microglia in the post-ischemic brain. Intracerebroventricular infusion of rats with AG490 (a JAK2 phosphorylation inhibitor) prevented the post-ischemic JAK2 and STAT3 phosphorylation and significantly decreased the infarct volume, number of apoptotic cells and neurological deficits, compared to vehicle control. Furthermore, intracerebral injection of siRNA specific for STAT3 led to curtailed STAT3 mRNA expression and phosphorylation, decreased infarct volume, fewer apoptotic cells and improved neurological function following transient middle cerebral artery occlusion. These studies show that JAK2-STAT3 activation plays a role in post-ischemic brain damage.

No abstract

AIH-induced respiratory plasticity and stem cell therapy have complementary translational potential to treat breathing deficits in patients with ALS.

Phrenic long-term facilitation (pLTF) following acute intermittent hypoxia (AIH) is a form of spinal, serotonin-dependent synaptic plasticity that requires reactive oxygen species (ROS) formation. We tested the hypothesis that spinal NADPH oxidase activity is a necessary source of ROS for pLTF. Sixty minutes post-AIH (three 5-min episodes of 11% O 2 , 5 min intervals), integrated phrenic and hypoglossal (XII) nerve burst amplitudes were increased from baseline, indicative of phrenic and XII LTF. Intrathecal injections (∼C 4 ) of apocynin or diphenyleneiodonium chloride (DPI), two structurally and functionally distinct inhibitors of the NADPH oxidase complex, attenuated phrenic, but not XII, LTF. Immunoblots from soluble (cytosolic) and particulate (membrane) fractions of ventral C 4 spinal segments revealed predominantly membrane localization of the NADPH oxidase catalytic subunit, gp91 phox , whereas membrane and cytosolic expression were both observed for the regulatory subunits, p47 phox and RAC1. Immunohistochemical analysis of fixed tissues revealed these same subunits in presumptive phrenic motoneurons of the C 4 ventral horn, but not in neighbouring astrocytes or microglia. Collectively, these data demonstrate that NADPH oxidase subunits localized within presumptive phrenic motoneurons are a major source of ROS necessary for AIH-induced pLTF. Thus, NADPH oxidase activity is a key regulator of spinal synaptic plasticity, and may be a useful pharmaceutical target in developing therapeutic strategies for respiratory insufficiency in patients with, for example, cervical spinal injury.

Phrenic long-term facilitation (pLTF) is a serotonin-dependent form of pattern-sensitive respiratory plasticity induced by intermittent hypoxia (IH), but not sustained hypoxia (SH). The mechanism(s) underlying pLTF pattern sensitivity are unknown. SH and IH may differentially regulate serine/threonine protein phosphatase activity, thereby inhibiting relevant protein phosphatases uniquely during IH and conferring pattern sensitivity to pLTF. We hypothesized that spinal protein phosphatase inhibition would relieve this braking action of protein phosphatases, thereby revealing pLTF after SH. Anesthetized rats received intrathecal (C4) okadaic acid (25 nM) before SH (25 min, 11% O 2 ). Unlike (vehicle) control rats, SH induced a significant pLTF in okadaic acid-treated rats that was indistinguishable from rats exposed to IH (three 5 min episodes, 11% O 2 ). IH and SH with okadaic acid may elicit pLTF by similar, serotonin-dependent mechanisms, because intravenous methysergide blocks pLTF in rats receiving IH or okadaic acid plus SH. Okadaic acid did not alter IH-induced pLTF. In summary, pattern sensitivity in pLTF may reflect differential regulation of okadaic acid-sensitive serine/threonine phosphatases; presumably, these phosphatases are less active during/after IH versus SH. The specific okadaic acid-sensitive phosphatase(s) constraining pLTF and their spatiotemporal dynamics during and/or after IH and SH remain to be determined.