Neoteric Role Of Quercetin In Visual Disorders.

Flavonoids are a family of secondary metabolites found in plants and fungi that exhibit strong antioxidant properties and low toxicity, making them potential candidates for medicinal use. Quercetin, a flavonoid present in various plant-based foods, has gained attention for its numerous biological benefits, including anti-inflammatory, anti-fibrosis, and antioxidant properties. The ocular surface research community has recently focused on quercetin's therapeutic potential for managing ocular diseases, such as dry eye, keratoconus, corneal inflammation, and neovascularization. In this paper, we discuss the role of quercetin for ocular disease prevention, highlighting its fundamental characteristics, common biological properties, and recent applications. By reviewing the latest research conducted in the last 10 years which was focused on novel herbal formulations for ocular diseases, we aim to provide insights into the role of quercetin in managing ocular diseases and offer perspectives on its potential as a therapeutic agent.

Leveraging single-cell RNA sequencing to unravel the impact of aging on stroke recovery mechanisms in mice.

Aging compromises the repair and regrowth of brain vasculature and white matter during stroke recovery, but the underlying mechanisms remain elusive. To understand how aging jeopardizes brain tissue repair after stroke, we performed single-cell transcriptomic profiling of young adult and aged mouse brains at acute (3 d) and chronic (14 d) stages after ischemic injury, focusing a priori on the expression of angiogenesis- and oligodendrogenesis-related genes. We identified unique subsets of endothelial cells (ECs) and oligodendrocyte (OL) progenitors in proangiogenesis and pro-oligodendrogenesis phenotypic states 3 d after stroke in young mice. However, this early prorepair transcriptomic reprogramming was negligible in aged stroke mice, consistent with the impairment of angiogenesis and oligodendrogenesis observed during the chronic injury stages after ischemia. In the stroke brain, microglia and macrophages (MG/MΦ) may drive angiogenesis and oligodendrogenesis through a paracrine mechanism. However, this reparative cell-cell cross talk between MG/MΦ and ECs or OLs is impeded in aged brains. In support of these findings, permanent depletion of MG/MΦ via antagonism of the colony-stimulating factor 1 receptor resulted in remarkably poor neurological recovery and loss of poststroke angiogenesis and oligodendrogenesis. Finally, transplantation of MG/MΦ from young, but not aged, mouse brains into the cerebral cortices of aged stroke mice partially restored angiogenesis and oligodendrogenesis and rejuvenated sensorimotor function and spatial learning and memory. Together, these data reveal fundamental mechanisms underlying the age-related decay in brain repair and highlight MG/MΦ as effective targets for promoting stroke recovery.

Neuron-targeted Knockout of APE1 Forces Premature Cognitive Impairment and Synaptic Dysfunction in Adult Mice.

Adaptable and consistent neural function relies at least in part on the ongoing repair of oxidative damage that can accumulate in the brain over a lifespan. To determine whether forebrain neuron-targeted knockout of AP endonuclease 1 (APE1), a critical enzyme in the base excision DNA repair pathway, contributes to neuronal impairments, we generated APE1 conditional knockout mice under the control of the CamKIIα promotor (APE1 cKO). Spatial learning and memory were tested using the Morris water maze. Synaptic markers, including synapsin, vGLUT, GABA1, and GAD were immunostained and quantified. Dendritic morphology and number were characterized using Golgi staining. Long-term potentiation (LTP) was measured in slices from the 6-month-old brain. APE1 cKO mice did not significantly differ from WT mice in the learning phase of the Morris water maze, but performed significantly worse during the memory phase of the Morris water maze. vGLUT, GABA1, and GAD immunostaining was significantly decreased in APE1 cKO mice without concomitant changes in the number of synapsin-positive structures, suggesting that neural networks may be impaired but not at the level of total presynaptic structures. Dendrites were reduced both in number and length of spines in APE1 cKO mice. APE1 cKO brain slices exhibited decreased LTP induction compared to WT brain slices. Together, these data indicate that the conditional loss of APE1 in forebrain neurons leads to a phenotype consistent with expedited brain aging.

Neuroprotection against ischemic stroke requires a specific class of early responder T cells in mice.

Immunomodulation holds therapeutic promise against brain injuries, but leveraging this approach requires a precise understanding of mechanisms. We report that CD8+CD122+CD49dlo T regulatory-like cells (CD8+ TRLs) are among the earliest lymphocytes to infiltrate mouse brains after ischemic stroke and temper inflammation; they also confer neuroprotection. TRL depletion worsened stroke outcomes, an effect reversed by CD8+ TRL reconstitution. The CXCR3/CXCL10 axis served as the brain-homing mechanism for CD8+ TRLs. Upon brain entry, CD8+ TRLs were reprogrammed to upregulate leukemia inhibitory factor (LIF) receptor, epidermal growth factor-like transforming growth factor (ETGF), and interleukin 10 (IL-10). LIF/LIF receptor interactions induced ETGF and IL-10 production in CD8+ TRLs. While IL-10 induction was important for the antiinflammatory effects of CD8+ TRLs, ETGF provided direct neuroprotection. Poststroke intravenous transfer of CD8+ TRLs reduced infarction, promoting long-term neurological recovery in young males or aged mice of both sexes. Thus, these unique CD8+ TRLs serve as early responders to rally defenses against stroke, offering fresh perspectives for clinical translation.

Genome-wide transcriptomic analysis of microglia reveals impaired responses in aged mice after cerebral ischemia.

Senescence-associated alterations in microglia may have profound impact on cerebral homeostasis and stroke outcomes. However, the lack of a transcriptome-wide comparison between young and aged microglia in the context of ischemia limits our understanding of aging-related mechanisms. Herein, we performed RNA sequencing analysis of microglia purified from cerebral hemispheres of young adult (10-week-old) and aged (18-month-old) mice five days after distal middle cerebral artery occlusion or after sham operation. Considerable transcriptional differences were observed between young and aged microglia in healthy brains, indicating heightened chronic inflammation in aged microglia. Following stroke, the overall transcriptional activation was more robust (>13-fold in the number of genes upregulated) in young microglia than in aged microglia. Gene clusters with functional implications in immune inflammatory responses, immune cell chemotaxis, tissue remodeling, and cell-cell interactions were markedly activated in microglia of young but not aged stroke mice. Consistent with the genomic profiling predictions, post-stroke cerebral infiltration of peripheral immune cells was markedly decreased in aged mice compared to young mice. Moreover, post-ischemic aged microglia demonstrated reduced interaction with neighboring neurons and diminished polarity toward the infarct lesion. These alterations in microglial gene response and behavior may contribute to aging-driven vulnerability and poorer recovery after ischemic stroke.

Endothelium-Targeted Deletion of microRNA-15a/16-1 Promotes Poststroke Angiogenesis and Improves Long-Term Neurological Recovery.

RATIONALE: Angiogenesis promotes neurological recovery after stroke and is associated with longer survival of stroke patients. Cerebral angiogenesis is tightly controlled by certain microRNAs (miRs), such as the miR-15a/16-1 cluster, among others. However, the function of the miR-15a/16-1 cluster in endothelium on postischemic cerebral angiogenesis is not known. OBJECTIVE: To investigate the functional significance and molecular mechanism of endothelial miR-15a/16-1 cluster on angiogenesis in the ischemic brain. METHODS AND RESULTS: Endothelial cell-selective miR-15a/16-1 conditional knockout (EC-miR-15a/16-1 cKO) mice and wild-type littermate controls were subjected to 1 hour middle cerebral artery occlusion followed by 28-day reperfusion. Deletion of miR-15a/16-1 cluster in endothelium attenuates post-stroke brain infarction and atrophy and improves the long-term sensorimotor and cognitive recovery against ischemic stroke. Endothelium-targeted deletion of the miR-15a/16-1 cluster also enhances post-stroke angiogenesis by promoting vascular remodeling and stimulating the generation of newly formed functional vessels, and increases the ipsilateral cerebral blood flow. Endothelial cell-selective deletion of the miR-15a/16-1 cluster up-regulated the protein expression of pro-angiogenic factors VEGFA (vascular endothelial growth factor), FGF2 (fibroblast growth factor 2), and their receptors VEGFR2 (vascular endothelial growth factor receptor 2) and FGFR1 (fibroblast growth factor receptor 1) after ischemic stroke. Consistently, lentiviral knockdown of the miR-15a/16-1 cluster in primary mouse or human brain microvascular endothelial cell cultures enhanced in vitro angiogenesis and up-regulated pro-angiogenic proteins expression after oxygen-glucose deprivation, whereas lentiviral overexpression of the miR-15a/16-1 cluster suppressed in vitro angiogenesis and down-regulated pro-angiogenic proteins expression. Mechanistically, miR-15a/16-1 translationally represses pro-angiogenic factors VEGFA, FGF2, and their receptors VEGFR2 and FGFR1, respectively, by directly binding to the complementary sequences within 3'-untranslated regions of those messenger RNAs. CONCLUSIONS: Endothelial miR-15a/16-1 cluster is a negative regulator for postischemic cerebral angiogenesis and long-term neurological recovery. Inhibition of miR-15a/16-1 function in cerebrovascular endothelium may be a legitimate therapeutic approach for stroke recovery.

MicroRNA-15a/16-1 Antagomir Ameliorates Ischemic Brain Injury in Experimental Stroke.

BACKGROUND AND PURPOSE: Dysregulation of the miR-15a/16-1 cluster in plasma has been reported in patients with stroke as a potential biomarker for diagnostic and prognostic use. However, the essential role and therapeutic potential of the miR-15a/16-1 cluster in ischemic stroke are poorly understood. This study is aimed at investigating the regulatory role of the miR-15a/16-1 cluster in ischemic brain injury and insight mechanisms. METHODS: Adult male miR-15a/16-1 knockout and wild-type mice, or adult male C57 BL/6J mice injected via tail vein with the miR-15a/16-1-specific inhibitor (antagomir, 30 pmol/g), were subjected to 1 hour of middle cerebral artery occlusion and 72 hours of reperfusion. The neurological scores, brain infarct volume, brain water content, and neurobehavioral tests were then evaluated and analyzed. To explore underlying signaling pathways associated with alteration of miR-15a/16-1 activity, major proinflammatory cytokines were measured by quantitative polymerase chain reaction or ELISA and antiapoptotic proteins were examined by Western blotting. RESULTS: Genetic deletion of the miR-15a/16-1 cluster or intravenous delivery of miR-15a/16-1 antagomir significantly reduced cerebral infarct size, decreased brain water content, and improved neurological outcomes in stroke mice. Inhibition of miR-15a/16-1 significantly decreased the expression of the proinflammatory cytokines interleukin-6, monocyte chemoattractant protein-1, vascular cell adhesion molecule 1, tumor necrosis factor alpha, and increased Bcl-2 and Bcl-w levels in the ischemic brain regions. CONCLUSIONS: Our data indicate that pharmacological inhibition of the miR-15a/16-1 cluster reduces ischemic brain injury via both upregulation of antiapoptotic proteins and suppression of proinflammatory molecules. These results suggest that the miR-15a/16-1 cluster is a novel therapeutic target for ischemic stroke.

Repetitive and Prolonged Omega-3 Fatty Acid Treatment After Traumatic Brain Injury Enhances Long-Term Tissue Restoration and Cognitive Recovery.

Traumatic brain injury (TBI) is one of the most disabling clinical conditions that could lead to neurocognitive disorders in survivors. Our group and others previously reported that prophylactic enrichment of dietary omega-3 polyunsaturated fatty acids (n-3 PUFAs) markedly ameliorate cognitive deficits after TBI. However, it remains unclear whether a clinically relevant therapeutic regimen with n-3 PUFAs administered after TBI would still offer significant improvement of long-term cognitive recovery. In the present study, we employed the decline of spatial cognitive function as a main outcome after TBI to investigate the therapeutic efficacy of post-TBI n-3 PUFA treatment and the underlying mechanisms. Mice were subjected to sham operation or controlled cortical impact, followed by random assignment to receive the following four treatments: (1) vehicle control; (2) daily intraperitoneal injections of n-3 PUFAs for 2 weeks, beginning 2 h after TBI; (3) fish oil dietary supplementation throughout the study, beginning 1 day after TBI; or (4) combination of treatments (2) and (3). Spatial cognitive deficits and chronic brain tissue loss, as well as endogenous brain repair processes such as neurogenesis, angiogenesis, and oligodendrogenesis, were evaluated up to 35 days after TBI. The results revealed prominent spatial cognitive deficits and massive tissue loss caused by TBI. Among all mice receiving post-TBI n-3 PUFA treatments, the combined treatment of fish oil dietary supplement and n-3 PUFA injections demonstrated a reproducible beneficial effect in attenuating cognitive deficits although without reducing gross tissue loss. Mechanistically, the combined treatment promoted post-TBI restorative processes in the brain, including generation of immature neurons, microvessels, and oligodendrocytes, each of which was significantly correlated with the improved cognitive recovery. These results indicated that repetitive and prolonged n-3 PUFA treatments after TBI are capable of enhancing brain remodeling and could be developed as a potential therapy to treat TBI victims in the clinic.

APE1/Ref-1 facilitates recovery of gray and white matter and neurological function after mild stroke injury.

A major hallmark of oxidative DNA damage after stroke is the induction of apurinic/apyrimidinic (AP) sites and strand breaks. To mitigate cell loss after oxidative DNA damage, ischemic cells rapidly engage the base excision-repair proteins, such as the AP site-repairing enzyme AP endonuclease-1 (APE1), also named redox effector factor-1 (Ref-1). Although forced overexpression of APE1 is known to protect against oxidative stress-induced neurodegeneration, there is no concrete evidence demonstrating a role for endogenous APE1 in the long-term recovery of gray and white matter following ischemic injury. To address this gap, we generated, to our knowledge, the first APE1 conditional knockout (cKO) mouse line under control of tamoxifen-dependent Cre recombinase. Using a well-established model of transient focal cerebral ischemia (tFCI), we show that induced deletion of APE1 dramatically enlarged infarct volume and impaired the recovery of sensorimotor and cognitive deficits. APE1 cKO markedly increased postischemic neuronal and oligodendrocyte degeneration, demonstrating that endogenous APE1 preserves both gray and white matter after tFCI. Because white matter repair is instrumental in behavioral recovery after stroke, we also examined the impact of APE1 cKO on demyelination and axonal conduction and discovered that APE1 cKO aggravated myelin loss and impaired neuronal communication following tFCI. Furthermore, APE1 cKO increased AP sites and activated the prodeath signaling proteins, PUMA and PARP1, after tFCI in topographically distinct manners. Our findings provide evidence that endogenous APE1 protects against ischemic infarction in both gray and white matter and facilitates the functional recovery of the central nervous system after mild stroke injury.

White matter injury and microglia/macrophage polarization are strongly linked with age-related long-term deficits in neurological function after stroke.

Most of the successes in experimental models of stroke have not translated well to the clinic. One potential reason for this failure is that stroke mainly afflicts the elderly and the majority of experimental stroke studies rely on data gathered from young adult animals. Therefore, in the present study we established a reliable, reproducible model of stroke with low mortality in aged (18month) male mice and contrasted their pathophysiological changes with those in young (2month) animals. To this end, mice were subjected to permanent tandem occlusion of the left distal middle cerebral artery (dMCAO) with ipsilateral common carotid artery occlusion (CCAO). Cerebral blood flow (CBF) was evaluated repeatedly during and after stroke. Reduction of CBF was more dramatic and sustained in aged mice. Aged mice exhibited more severe long-term sensorimotor deficits, as manifested by deterioration of performance in the Rotarod and hanging wire tests up to 35d after stroke. Aged mice also exhibited significantly worse long-term cognitive deficits after stroke, as measured by the Morris water maze test. Consistent with these behavioral observations, brain infarct size and neuronal tissue loss after dMCAO were significantly larger in aged mice at 2d and 14d, respectively. The young versus aged difference in neuronal tissue loss, however, did not persist until 35d after dMCAO. In contrast to the transient difference in neuronal tissue loss, we found significant and long lasting deterioration of white matter in aged animals, as revealed by the loss of myelin basic protein (MBP) staining in the striatum at 35d after dMCAO. We further examined the expression of M1 (CD16/CD32) and M2 (CD206) markers in Iba-1(+) microglia by double immunofluorescent staining. In both young and aged mice, the expression of M2 markers peaked around 7d after stroke whereas the expression of M1 markers peaked around 14d after stroke, suggesting a progressive M2-to-M1 phenotype shift in both groups. However, aged mice exhibited significantly reduced M2 polarization compared to young adults. Remarkably, we discovered a strong positive correlation between favorable neurological outcomes after dMCAO and MBP levels or the number of M2 microglia/macrophages. In conclusion, our studies suggest that the distal MCAO stroke model consistently results in ischemic brain injury with long-term behavioral deficits, and is therefore suitable for the evaluation of long-term stroke outcomes. Furthermore, aged mice exhibit deterioration of functional outcomes after stroke and this deterioration is linked to white matter damage and reductions in M2 microglia/macrophage polarization.

Blalock-Taussig shunt: experience from the developing world.

BACKGROUND: Palliative procedures have a role in congenital cardiac malformations that do not permit a complete early repair, and in centres where facilities for complete early repair do not exist. The lack of data on modified Blalock-Taussig shunt from developing countries prompted this analysis. METHODS: We report a retrospective study of 70 Blalock-Taussig shunt procedures in 63 patients over an 8-year period. Most of the procedures (54.0%) were done on children less than 4 months of age. Thirty-nine (58%) patients had Tetralogy of Fallot; the remaining patients had a wide spectrum of lesions. RESULTS: In the first year of the review period, the classical Blalock-Taussig shunt was done in six patients (9.5%) and the modified Blalock-Taussig shunt was used thereafter. In 49 patients who were followed up long term, clinical congestive cardiac failure developed in three (6%) and shunt failure was reported in 10 (14%). Of the 16 (33%) total deaths, six had serious comorbid conditions preoperatively. CONCLUSIONS: The Blalock-Taussig shunt is a relatively safe palliative procedure, requiring fewer resources and less expertise than corrective surgery, making it a suitable option in developing countries.