Explore the vast range of titles available.

Traumatic optic neuropathy (TON) is characterized by visual dysfunction after indirect or direct injury to the optic nerve following blunt head trauma. TON is associated with increased oxidative stress and inflammation resulting in retinal ganglion cell (RGC) death. Remote ischemic post-conditioning (RIC) has been shown to enhance endogenous protective mechanisms in diverse disease models including stroke, vascular cognitive impairment (VCI), retinal injury and optic nerve injury. However, the protective mechanisms underlying the improvement of retinal function and RGC survival after RIC treatment remain unclear. Here, we hypothesized that RIC therapy may be protective following TON by preventing RGC death, oxidative insult and inflammation in the mouse retina. To carry out the study, mice were divided in three different groups (Control, TON and TON + RIC). We harvested retinal tissue 5 days after TON induction for western blotting and histochemical analysis. We observed increased TON-induced retinal cell death compared with controls by cleaved caspase-3 immunohistochemistry. Furthermore, the TON cohort demonstrated increased TUNEL positive cells which were significantly attenuated by RIC. Immunofluorescence data showed that oxidative stress markers dihydroethidium (DHE), NOX-2 and nitrotyrosine expression were elevated in the TON group relative to controls and RIC therapy significantly reduced the expression level of these markers. Next, we found that the proinflammatory cytokine TNF-α was increased and anti-inflammatory IL-10 was decreased in plasma of TON animals, and RIC therapy reversed this expression level. Interestingly, western blotting of retinal tissue showed that RGC marker Brn3a and tight junction proteins (ZO-1 and Occludin), and AMPKα1 expression were downregulated in the TON group compared to controls. However, RIC significantly increased the expression levels of these proteins. Together these data suggest that RIC therapy activates endogenous protective mechanisms which may attenuate TON-induced oxidative stress and inflammation, and improves BRB integrity.

Vascular dysfunction resulting in compromised blood-brain barrier (BBB) integrity is evident in aging and disease. Although the complement C3a/C3a receptor (C3a/C3aR) axis influences normal brain aging and disease progression, the mechanisms governing endothelial C3aR-mediated neurovascular inflammation and BBB permeability remain unexplored. In this issue of the JCI, Propson et al. investigated endothelial C3a/C3aR signaling in normal, aged, and neurodegenerative mouse models. Endothelial C3aR signaling modulated age-dependent increases in VCAM1, initiated peripheral lymphocyte infiltration, and enhanced microglial activity. Increased calcium release downstream of C3aR signaling disrupted the vascular endothelial cadherin (VE-cadherin) junctions, increased BBB permeability, and degraded vascular structure and function. Mice lacking C3aR (C3ar1-/-) and mice treated with a C3aR antagonist showed attenuated age-related microglial reactivity and neurodegeneration. These results confirm that complement-mediated signaling impacts vascular health and BBB function in normal aging and neurodegenerative disease, suggesting that complement inhibitors represent a therapeutic option for cerebral microvascular dysfunction.

Vascular dysfunction resulting In compromised blood-brain barrier (BBB) Integrity is evident in aging and disease. Although the complement C3a/ C3a receptor (C3a/C3aR) axis influences normal brain aging and disease progression, the mechanisms governing endothelial C3aR-mediated neurovascular inflammation and BBB permeability remain unexplored. In this issue of theJCI, Propson et al. investigated endothelial C3a/ C3aR signaling in normal, aged, and neurodegenerative mouse models. Endothelial C3aR signaling modulated age-dependent increases in VCAM1, initiated peripheral lymphocyte infiltration, and enhanced microglial activity. Increased calcium release downstream of C3aR signaling disrupted the vascular endothelial cadherin (VE-cadherin) junctions, increased BBB permeability, and degraded vascular structure and function. Mice lacking C3aR (C3ar1-/-) and mice treated with a C3aR antagonist showed attenuated age-related microglial reactivity and neurodegeneration. These results confirm that complement-mediated signaling impacts vascular health and BBB function in normal aging and neurodegenerative disease, suggesting that complement inhibitors represent a therapeutic option for cerebral microvascular dysfunction.

Brain endothelial cells play an important role in maintaining blood flow homeostasis in the brain. Cerebral ischemia is a major cause of endothelial dysfunction which can disrupt the blood–brain barrier (BBB). Oxygen–glucose deprivation (OGD)/reperfusion promote cell death and BBB breakdown in brain endothelial cells. Acetyl-11-keto-β-boswellic acid (AKBA), a biologically active phytoconstituent of the medicinal plant Boswellia serrata, has been shown to be protective against various inflammatory diseases as well as ischemic brain injury. The molecular mechanisms underlying these beneficial characteristics of AKBA are poorly understood. We subjected bEND.3 cells to OGD/reperfusion to investigate the protective role of AKBA in this model. We found that AKBA treatment attenuated endothelial cell death and oxidative stress assessed by means of TUNEL assay, cleaved-caspase-3, and dihydroethidium (DHE) staining. Furthermore, OGD downregulated tight junction proteins ZO-1 and Occludin levels, and increased the expressions of inflammatory cytokines TNF-α, ICAM-1, and complement C3a receptor (C3aR). We also noticed the increased phosphorylation of ERK 1/2 in bEND.3 cells in OGD group. AKBA treatment significantly attenuated expression levels of these inflammatory proteins and prevented the degradation of ZO-1 and Occludin following OGD. In conclusion, AKBA treatment provides protection against endothelial cell dysfunction following OGD by attenuating oxidative stress and inflammation.

The complement system is a key regulator of the innate immune response against diseased tissue that functions across multiple organ systems. Dysregulation of complement contributes to the pathogenesis of a number of neurological diseases including stroke. The C3a anaphylatoxin, via its cognate C3a receptor (C3aR), mediates inflammation by promoting breakdown of the blood–brain barrier and the massive infiltration of leukocytes into ischemic brain in experimental stroke models. Studies utilizing complement deficient mice as well as pharmacologic C3aR antagonists have shown a reduction in tissue injury and mortality in murine stroke models. The development of tissue-specific C3aR knockout mice and more specific C3aR antagonists is warranted to facilitate our understanding of the role of the C3aR in brain ischemia with the ultimate goal of clinical translation of therapies targeting C3aR in stroke patients.

Vascular contributions to cognitive impairment and dementia (VCID) secondary to chronic mild-moderate cerebral ischemia underlie a significant percentage of cases of dementia. We previously reported that either genetic deficiency of the complement C3a receptor (C3aR) or its pharmacological inhibition protects against cerebral ischemia in rodents, while others have implicated C3aR in the pathogenesis seen in rodent transgenic models of Alzheimer’s disease. In the present study, we evaluated the role of complement C3a-C3aR signaling in the onset and progression of VCID. We utilized the bilateral common carotid artery stenosis (BCAS) model to induce VCID in male C57BL/6 wild-type and C3aR-knockout (C3aR −/− ) mice. Cerebral blood flow (CBF) changes, hippocampal atrophy (HA), white matter degeneration (WMD), and ventricular size were assessed at 4 months post-BCAS using laser speckle contrast analysis (LSCI) and magnetic resonance imaging (MRI). Cognitive function was evaluated using the Morris water maze (MWM), and novel object recognition (NOR), immunostaining, and western blot were performed to assess the effect of genetic C3aR deletion on post-VCID outcomes. BCAS resulted in decreased CBF and increased HA, WMD, and neurovascular inflammation in WT (C57BL/6) compared to C3aR −/− (C3aR-KO) mice. Moreover, C3aR −/− mice exhibited improved cognitive function on NOR and MWM relative to WT controls. We conclude that over-activation of the C3a/C3aR axis exacerbates neurovascular inflammation leading to poor VCID outcomes which are mitigated by C3aR deletion. Future studies are warranted to dissect the role of cell-specific C3aR in VCID.