Relatively few catalytic systems are able to control the stereochemistry of electronically excited organic intermediates. Here we report the discovery that a chiral Lewis acid complex can catalyze ...triplet energy transfer from an electronically excited photosensitizer. We applied this strategy to asymmetric 2 + 2 photocycloadditions of 2'-hydroxychalcones, using tris(bipyridyl) ruthenium(ll) as a sensitizer. A variety of electrochemical, computational, and spectroscopic data rule out substrate activation by means of photoinduced electron transfer and instead support a mechanism in which Lewis acid coordination dramatically lowers the triplet energy of the chalcone substrate. We expect that this approach will enable chemists to more broadly apply their detailed understanding of chiral Lewis acid catalysis to stereocontrol in reactions involving electronically excited states.
Neuronal apoptosis is a common and critical pathology following subarachnoid hemorrhage (SAH). We investigated the anti-apoptotic property of fibroblast growth factor (FGF)-2 after SAH in rats. A ...total of 289 rats underwent endovascular perforation to induce SAH or sham operation. Three dosages (3, 9, or 27 μg) of recombinant FGF-2 (rFGF-2) or vehicle was administered intranasally to rats 30 min after SAH induction. The pan-FGF receptor (FGFR) inhibitor PD173074 or vehicle was administered intracerebroventricularly (i.c.v.) 1 h before modeling, in addition to rFGF-2 treatment. Small interfering ribonucleic acid (siRNA) for FGFR1 and FGFR3 or scrambled siRNA was administered i.c.v. 48 h before SAH induction in addition to rFGF-2 treatment. Anti-FGF-2 neutralizing antibody or normal mouse immunoglobulin G (IgG) was administered i.c.v. 1 h before SAH model. Neurobehavioral tests, SAH severity, brain water content, immunofluorescence, Fluoro-Jade C, TUNEL staining, and western blot were evaluated. The expression of FGF-2, FGFR1, and FGFR3 increased after SAH. FGFR1 and FGFR3 were expressed in the neurons. Nine micrograms of FGF-2 alleviated neurological impairments, brain edema, and neuronal apoptosis following SAH. A rFGF-2 treatment improved motor skill learning and spatial memory and increased the number of surviving neurons postinjury to 28 days after SAH. PD173074 abolished the anti-apoptotic effects of rFGF-2 via suppression of the expression of PI3k, phosphorylated Akt (p-Akt), and Bcl-2 leading to enhancement of the expression of Bax. FGFR3 siRNA worsened neurobehavioral function and suppressed the expression of PI3k, p-Akt, and Bcl-2 rather than FGFR1 siRNA in SAH rats treated with rFGF-2. Anti-FGF-2 neutralizing antibody suppressed the expression of PI3k and p-Akt after SAH. FGF-2 may be a promising therapy to reduce post-SAH neuronal apoptosis via activation of the FGFR3/PI3k/Akt signaling pathway.
Stroke is one of the leading causes of mortality and morbidity worldwide. The bloodbrain barrier (BBB) is a characteristic structure of microvessel within the brain. Under normal physiological ...conditions, the BBB plays a role in the prevention of harmful substances entering into the brain parenchyma within the central nervous system. However, stroke stimuli induce the breakdown of BBB leading to the influx of cytotoxic substances, vasogenic brain edema, and hemorrhagic transformation. Therefore, BBB disruption is a major complication, which needs to be addressed in order to improve clinical outcomes in stroke. In this review, we first discuss the structure and function of the BBB. Next, we discuss the progress of the techniques utilized to study BBB breakdown in in-vitro and in-vivo studies, along with biomarkers and imaging techniques in clinical settings. Lastly, we highlight the mechanisms of stroke-induced neuroinflammation and apoptotic process of endothelial cells causing BBB breakdown, and the potential therapeutic targets to protect BBB integrity after stroke. Secondary products arising from stroke-induced tissue damage provide transformation of myeloid cells such as microglia and macrophages to pro-inflammatory phenotype followed by further BBB disruption via neuroinflammation and apoptosis of endothelial cells. In contrast, these myeloid cells are also polarized to anti-inflammatory phenotype, repairing compromised BBB. Therefore, therapeutic strategies to induce anti-inflammatory phenotypes of the myeloid cells may protect BBB in order to improve clinical outcomes of stroke patients.
The activation of C-C chemokine receptor type 1 (CCR1) has been shown to be pro-inflammatory in several animal models of neurological diseases. The objective of this study was to investigate the ...activation of CCR1 on neuroinflammation in a mouse model of intracerebral hemorrhage (ICH) and the mechanism of CCR1/tetratricopeptide repeat 1 (TPR1)/extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway in CCR1-mediated neuroinflammation. Adult male CD1 mice (
n
= 210) were used in the study. The selective CCR1 antagonist Met-RANTES was administered intranasally at 1 h after autologous blood injection. To elucidate potential mechanism, a specific ERK1/2 activator (ceramide C6) was administered prior to Met-RANTES treatment; CCR1 activator (recombinant CCL5, rCCL5) and TPR1 CRISPR were administered in naïve mouse. Neurobehavioral assessments, brain water content, immunofluorescence staining, and western blot were performed. The endogenous expressions of CCR1, CCL5, TPR1, and p-ERK1/2 were increased in the brain after ICH. CCR1 were expressed on microglia, neurons, and astrocytes. The inhibition of CCR1 with Met-RANTES improved neurologic function, decreased brain edema, and suppressed microglia/macrophage activations and neutrophil infiltration after ICH. Met-RANTES treatment decreased expressions of CCR1, TPR1, p-ERK, TNF-α, and IL-1β, which was reversed by ceramide C6. The brain CCR1 activation by rCCL5 injection in naïve mouse resulted in neurological deficits and increased expressions of CCR1, TPR1, p-ERK, TNF-α, and IL-1β. These detrimental effects of rCCL5 were reversed by TPR1 knockdown using TPR1 CRISPR. Our study demonstrated that CCR1 activation promoted neuroinflammation through CCR1/TPR1/ERK1/2 signaling pathway after ICH in mice. CCR1 inhibition with Met-RANTES attenuated neuroinflammation, thereby reducing brain edema and improving neurobehavioral functions. Targeting CCR1 activation may provide a promising therapeutic approach in the management of ICH patients.
Oxidative stress and neuronal apoptosis have been demonstrated to be key features in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Previous studies have indicated that Mas receptor ...activation initiates an anti-oxidative and anti-apoptotic role in the brain. However, whether Mas activation can attenuate oxidative stress and neuronal apoptosis after SAH remains unknown. To investigate the beneficial effect of Mas on oxidative stress injury and neuronal apoptosis induced by SAH, a total of 196 rats were subjected to an endovascular perforation model of SAH. AVE 0991 (AVE), a selective agonist of Mas, was administered intranasally 1 h after SAH induction. A779, a selective inhibitor of Mas, and small interfering ribonucleic acid (siRNA) for UCP-2 were administered by intracerebroventricular (i.c.v) injection at 1 h and 48 h before SAH induction respectively. Neurological tests, immunofluorescence, TUNEL, Fluoro-Jade C, DHE staining, and Western blot experiments were performed. We found that Mas activation with AVE significantly improved neurobehavioral scores and reduced oxidative stress and neuronal apoptosis in SAH+AVE group compared with SAH+vehicle group. Moreover, AVE treatment significantly promoted phosphorylation of CREB and the expression UCP-2, as well as upregulated expression of Bcl-2 and downregulation of Romo-1 and Bax. The protective effects of AVE were reversed by i.c.v injection of A779 and UCP-2 siRNA in SAH+AVE+A779 and SAH+AVE+UCP-2 siRNA groups, respectively. In conclusion, our data provides evidence that Mas activation with AVE reduces oxidative stress injury and neuronal apoptosis through Mas/PKA/p-CREB/UCP-2 pathway after SAH. Furthermore, our study indicates that Mas may be a novel therapeutic treatment target in early brain injury of SAH.
Subarachnoid hemorrhage (SAH) is a life-threatening subtype of stroke with high mortality and disabilities. Retinoid X receptor (RXR) has been shown to be neuroprotective against ischemia/reperfusion ...injury. This study aimed to investigate the effects of the selective RXR agonist bexarotene on neuroinflammation in a rat model of SAH.
Two hundred male Sprague-Dawley rats were used. The endovascular perforation induced SAH. Bexarotene was administered intraperitoneally at 1 h after SAH induction. To investigate the underlying mechanism, the selective RXR antagonist UVI3003 and RXR siRNA or SIRT6 inhibitor OSS128167 was administered via intracerebroventricular 1 h before SAH induction. Post-SAH assessments including SAH grade, neurological score, brain water content, Western blot, and immunofluorescence were performed.
The endogenous RXR and sirtuin 6 (SIRT6) protein levels were increased after SAH. Bexarotene treatment significantly reduced brain edema and improved the short-/long-term neurological deficit after SAH. Mechanistically, bexarotene increased the levels of PPARγ and SIRT6; decreased the expression of phosphorylated FoxO3a (p-FoxO3a), IL-6, IL-1β, and TNF-a; and inhibited the microglia activation and neutrophils infiltration at 24 h after SAH. Either UVI3003, OSS128167, or RXR siRNA abolished the neuroprotective effects of bexarotene and its regulation on protein levels of PPARγ/SIRT6/p-FoxO3a after SAH.
The activation of RXR by bexarotene attenuated neuroinflammation and improved neurological deficits after SAH. The anti-neuroinflammatory effect was at least partially through regulating PPARγ/SIRT6/FoxO3a pathway. Bexarotene may be a promising therapeutic strategy in the management of SAH patients.
Subarachnoid hemorrhage (SAH) is the most devastating form of stroke. Reducing neuronal apoptosis is an important countermeasure against early brain injury (EBI) after SAH. Recent evidence indicates ...that OX40-OX40L coupling is critical for cell survival and proliferation. Current study was performed to detect the role of recombinant OX40 (ReOX40) against neuronal apoptosis after SAH. The endovascular perforation model of SAH was performed on Sprague-Dawley (SD) rats. ReOX40 was injected intracerebroventricularly (i.c.v) 1 h after SAH induction and the following methods were employed: neurological function evaluation, immunofluorescence staining, fluoro-Jade C staining, and western blot. To study the underlying precise molecular mechanism, small interfering ribonucleic acid (siRNA) for OX40L and a specific inhibitor of PI3K, LY294002, were injected i.c.v. into SAH + ReOX40 rats before induction of SAH. When compared with sham rats, the expression of OX40 and OX40L was seen to decrease in the brain at 24 h after SAH induction. Administration of ReOX40 (5 μg/kg) increased expression of the OX40L, reduced the neuronal apoptosis, and improved short and long-term neurological function deficits. Furthermore, ReOx40 heightened activation of OX40L/PI3K/AKT axis, increased the downstream anti-apoptotic protein (Bcl2, Bcl-XL), and depressed the apoptotic protein (cleaved caspase 3, Bax). However, the protective effects of ReOX40 were abolished by the administration of OX40L siRNA and LY294002, respectively. These results demonstrate that ReOX40 attenuates neuronal apoptosis through OX40-OX40L/PI3K/AKT pathway in EBI after SAH.
Mitochondrial dysfunction is involved in the mechanism of early brain injury (EBI) following subarachnoid hemorrhage (SAH). Blood-brain barrier disruption is a devastating outcome in the early stage ...of SAH. In this study, we aimed to investigate the role of a mitochondria-related drug Mitoquinone (MitoQ) in blood-brain barrier disruption after SAH in rats.
A total of 181 male Sprague–Dawley SAH rats with the endovascular perforation model were utilized. Intraperitoneal MitoQ was given 1 h (h) post-SAH. Cerebroventricular ML385, an inhibitor of NF-E2-related factor 2 (Nrf2) and Small interfering ribonucleic acid (siRNA) for Prohibitin 2 (PHB2) were injected respectively 24 h and 48 h before SAH. Neurological function evaluation was performed before sacrifice. SAH grade was measured during the sacrifice of each animal. Brain water content was performed at 24 h. Co-immunoprecipitation was used to demonstrate the relationship of proteins Nrf2 and PHB2. Mitochondrial and cytoplasmic fractions were gathered using mitochondria isolation kits. Pathway related proteins were investigated with Western blot and immunofluorescence staining. Transmission electron microscopy was performed for mitochondrial morphology.
Expression of Nrf2 levels peaked at the 3 h time point following SAH and then decreased to normal levels at 24 h, while PHB2 and Optic Atrophy 1 (OPA1) decreased at 24 h and 72 h after SAH compared with the Sham group. MitoQ treatment attenuated neurological deficits and brain edema, thereby resulting in a decreased expression of Albumin, while an increase of Nrf2, PHB2, OPA1 and Claudin-5 proteins compared with SAH + vehicle group. With co-immunoprecipitation, Nrf2 and PHB2 were further demonstrated to show their interaction. And MitoQ administration lead to more binding of the two proteins. ML385 abolished the effects of MitoQ on neurobehavior and protein levels post-SAH. Similarly, PHB2 siRNA reversed the neuroprotection of MitoQ administration with the decreased expression of PHB2 and OPA1 after SAH. Further, MitoQ treatment improved mitochondrial morphology after SAH with an increase of PHB2 and OPA1 in mitochondrial extraction.
MitoQ attenuates blood-brain barrier disruption via Nrf2/PHB2/OPA1 pathway after SAH in rats. MitoQ may serve as a potential therapeutic strategy for SAH patients.
Understanding the origin and maintenance of phenotypic variation, particularly across a continuous spatial distribution, represents a key challenge in evolutionary biology. For this, animal venoms ...represent ideal study systems: they are complex, variable, yet easily quantifiable molecular phenotypes with a clear function. Rattlesnakes display tremendous variation in their venom composition, mostly through strongly dichotomous venom strategies, which may even coexist within a single species. Here, through dense, widespread population-level sampling of the Mojave rattlesnake, Crotalus scutulatus, we show that genomic structural variation at multiple loci underlies extreme geographical variation in venom composition, which is maintained despite extensive gene flow. Unexpectedly, neither diet composition nor neutral population structure explain venom variation. Instead, venom divergence is strongly correlated with environmental conditions. Individual toxin genes correlate with distinct environmental factors, suggesting that different selective pressures can act on individual loci independently of their co-expression patterns or genomic proximity. Our results challenge common assumptions about diet composition as the key selective driver of snake venom evolution and emphasize how the interplay between genomic architecture and local-scale spatial heterogeneity in selective pressures may facilitate the retention of adaptive functional polymorphisms across a continuous space.
: Slit2 is an extracellular matrix protein that regulates migration of developing axons during central nervous system (CNS) development. Roundabout (Robo) receptors expressed by various cell types in ...the CNS, mediate intracellular signal transduction pathways for Slit2. Recent studies indicate that Slit2 plays important protective roles in a myriad of processes such as cell migration, immune response, vascular permeability, and angiogenesis in CNS pathologies.
: This review provides an overview of the diverse functions of Slit2 in CNS disorders and discusses the potential of Slit2 as a therapeutic target. We reviewed preclinical studies reporting the role of Slit2 in various CNS disease models, transgenic animal research, and rodent models that utilized Slit2 as a therapy.
: Slit2 exerts a wide array of beneficial effects ranging from anti-migration, blood-brain barrier (BBB) protection, inhibition of peripheral immune cell infiltration, and anti-apoptosis in various disease models. However, a dual role of Slit2 in endothelial permeability has been observed in transgenic animals. Further research on Slit2 will be crucial including key issues such as effects of transgenic overexpression versus exogenous Slit2, function of Slit2 dependent on cellular expression of Robo receptors and the underlying pathology for potential clinical translation.
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