MicroRNAs (miRNAs) are ~22 nucleotides long, noncoding RNAs that control cellular function by either degrading mRNAs or arresting their translation. To understand their functional significance in ischemic pathophysiology, we profiled miRNAs in adult rat brain as a function of reperfusion time after transient middle cerebral artery occlusion. Of the 238 miRNAs evaluated, 8 showed increased and 12 showed decreased expression at least at 4 out of 5 reperfusion time points studied between 3 h and 3 days compared with sham. Of those, 17 showed >5 fold change. Bioinformatics analysis indicated a correlation between miRNAs altered to several mRNAs known to mediate inflammation, transcription, neuroprotection, receptors function, and ionic homeostasis. Antagomir-mediated prevention of mir-145 expression led to an increased protein expression of its downstream target superoxide dismutase-2 in the postischemic brain. In silico analysis showed sequence complementarity of eight miRNAs induced after focal ischemia to 877 promoters indicating the possibility of noncoding RNA-induced activation of gene expression. The mRNA expression of the RNases Drosha and Dicer, cofactor Pasha, and the pre-miRNA transporter exportin-5, which modulate miRNA biogenesis, were not altered after transient middle cerebral artery occlusion. Thus, the present studies indicate a critical role of miRNAs in controlling mRNA transcription and translation in the postischemic brain.

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

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-