Poststroke Induction of α-Synuclein Mediates Ischemic Brain Damage.

UNLABELLED: α-Synuclein (α-Syn), one of the most abundant proteins in the CNS, is known to be a major player in the neurodegeneration observed in Parkinson's disease. We currently report that transient focal ischemia upregulates α-Syn protein expression and nuclear translocation in neurons of the adult rodent brain. We further show that knockdown or knock-out of α-Syn significantly decreases the infarction and promotes better neurological recovery in rodents subjected to focal ischemia. Furthermore, α-Syn knockdown significantly reduced postischemic induction of phospho-Drp1, 3-nitrotyrosine, cleaved caspase-3, and LC-3 II/I, indicating its role in modulating mitochondrial fragmentation, oxidative stress, apoptosis, and autophagy, which are known to mediate poststroke neuronal death. Transient focal ischemia also significantly upregulated serine-129 (S129) phosphorylation (pα-Syn) of α-Syn and nuclear translocation of pα-Syn. Furthermore, knock-out mice that lack PLK2 (the predominant kinase that mediates S129 phosphorylation) showed better functional recovery and smaller infarcts when subjected to transient focal ischemia, indicating a detrimental role of S129 phosphorylation of α-Syn. In conclusion, our studies indicate that α-Syn is a potential therapeutic target to minimize poststroke brain damage. SIGNIFICANCE STATEMENT: Abnormal aggregation of α-synuclein (α-Syn) has been known to cause Parkinson's disease and other chronic synucleinopathies. However, even though α-Syn is linked to pathophysiological mechanisms similar to those that produce acute neurodenegerative disorders, such as stroke, the role of α-Syn in such disorder is not clear. We presently studied whether α-Syn mediates poststroke brain damage and more importantly whether preventing α-Syn expression is neuroprotective and leads to better physiological and functional outcome after stroke. Our study indicates that α-Syn is a potential therapeutic target for stroke therapy.

Mutual induction of transcription factor PPARγ and microRNAs miR-145 and miR-329.

MicroRNAs (miRNAs) are small non-coding RNAs that are known to control mRNA translation. Most miRNAs are transcribed from specific genes with well-defined promoters located throughout the genome. The mechanisms that control miRNA expression under normal and pathological conditions are not yet understood clearly. Peroxisome proliferator-activated receptor (PPAR) γ is a ligand-activated transcription factor that is extensively distributed in the CNS. PPARγ activation induces neuroprotection by modulating genes that contain peroxisome proliferator response elements (PPREs) in their promoters. We presently evaluated if PPARγ modulates miRNA expression. When adult rats were treated with PPARγ agonist rosiglitazone, expression of 28 miRNAs altered significantly (12 up- and 16 down-regulated; 3-119 fold) in the cerebral cortex compared to vehicle-treated controls. In silico analysis showed 1-5 PPREs in the putative promoter regions (within 1 Kb upstream of the transcription start site) of these miRNA genes. Cotransfection with a PPARγ constitutively expressing vector significantly induced the miR-145 and miR-329 promoter vectors (each have four PPREs), which was curtailed by point mutations of PPREs in their promoters. Interestingly, the PPARγ promoter has binding sites for both these miRNAs and transfection with miR-329 mimic and miR-145 mimic induced the PPARγ expression. Thus, these studies show a cyclical induction of miRNAs and PPARγ, indicating that the pleiotropic beneficial effects of PPARγ agonists might be modulated in part by miRNAs and their down-stream mRNAs. We proposed that promoters of many microRNAs contain the binding sites for the transcription factor PPARγ. Activation of PPARγ modulates the expression of these microRNAs. Two such PPARγ-responsive microRNAs (miR-145 and miR-329) bind to PPARγ promoter to induce its expression. This indicates the presence of a feedback loop by which transcription factors and microRNAs can modulate each other.

Electrospun poly(ε-caprolactone)-based skin substitutes: In vivo evaluation of wound healing and the mechanism of cell proliferation.

In the present study, we have fabricated electrospun poly(ε-caprolactone)-based membranes, characterized and studied the in vivo cell migration and proliferation and wound healing activity. Moreover, we did not seed any cells prior to the animal implantation and we could observe excellent fibroblast attachment and cell proliferation. Further full thickness excision wound on guinea pig completely healed within 35 days. We could reach in an assumption that the enhanced cell proliferation and wound healing might be due to the surface degradation of the polymer under physiological conditions and the formation of functional groups like hydroxyl and carboxyl groups that promoted cell proliferation in a cell adhesion protein mediated mechanism. This study is a novel tissue engineering concept for the reconstruction of a damaged tissue without the in vitro cell seeding and proliferation prior to the in vivo implantation.