Brain edema formation and complement activation in a rat model of subarachnoid hemorrhage

Systemic Inflammation after Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is one of the most severe neurological disorders, with a high mortality rate and severe disabling functional sequelae. Systemic inflammation following hemorrhagic stroke may play an important role in mediating intracranial and extracranial tissue damage. Previous studies showed that various systemic inflammatory biomarkers might be useful in predicting clinical outcomes. Anti-inflammatory treatment might be a promising therapeutic approach for improving the prognosis of patients with aSAH. This review summarizes the complicated interactions between the nervous system and the immune system.

Up-regulation of circARF3 reduces blood-brain barrier damage in rat subarachnoid hemorrhage model via miR-31-5p/MyD88/NF-κB axis

Inflammation events have been found to aggravate brain injury and blood-brain barrier (BBB) damage following subarachnoid hemorrhage (SAH). This study probed the role and mechanism of a novel circRNA, circARF3, in regulating the BBB injury in SAH rats and hypoxia-induced vascular endothelial cell (VEC) injury in vitro. Levels of circARF3 and miR-31-5p were monitored by RT-PCR. The expression of inflammatory factors IL-1β and TNF-α was verified by ELISA. In vivo SAH model was constructed in Sprague Dawley (SD) rats. The BBB integrity and cerebral edema, as well as the neurological functions of the rats were evaluated. The apoptotic neurons and microglia in brain lesions were examined by immunohistochemistry (IHC). The MyD88/NF-κB pathway was tested by Western blot. Furthermore, gain-of functional assay were constructed to explore the effects of circARF3 and miR-31-5p in primary cultured brain microvascular endothelial cell (BMEC) injury and microglial inflammation induced by oxygen and glucose deprivation (OGD). circARF3 was significantly down-regulated in plasma and CSF in SAH patients with higher Fisher stages. In the SAH rat model, overexpressing circARF3 improved BBB integrity and neurological score, decreased neuronal apoptosis and microglial activation in ipsilateral basal cortex, with declined miR-31-5p expression and MyD88-NF-κB activation. In vitro, overexpressing circARF3 attenuated OGD-mediated integrity destruction of BMECs and microglial induced neuroinflammation, while overexpressing miR-31-5p had opposite effects. Mechanistically, circARF3 sponged miR-31-5p as an endogenous competitive RNA and dampens its expression, thus inactivating MyD88-NF-κB pathway. CircARF3 attenuates BBB destruction in SAH rats by regulating the miR-31-5p-activated MyD88-NF-κB pathway.

Dysferlin-deficiency has greater impact on function of slow muscles, compared with fast, in aged BLAJ mice

Dysferlinopathies are a form of muscular dystrophy caused by gene mutations resulting in deficiency of the protein dysferlin. Symptoms manifest later in life in a muscle specific manner, although the pathomechanism is not well understood. This study compared the impact of dysferlin-deficiency on in vivo and ex vivo muscle function, and myofibre type composition in slow (soleus) and fast type (extensor digitorum longus; EDL) muscles using male dysferlin-deficient (dysf^-/-) BLAJ mice aged 10 months, compared with wild type (WT) C57Bl/6J mice. There was a striking increase in muscle mass of BLAJ soleus (+25%) (p<0.001), with no strain differences in EDL mass, compared with WT. In vivo measures of forelimb grip strength and wheel running capacity showed no strain differences. Ex vivo measures showed the BLAJ soleus had faster twitch contraction (-21%) and relaxation (-20%) times, and delayed post fatigue recovery (ps<0.05); whereas the BLAJ EDL had a slower relaxation time (+11%) and higher maximum rate of force production (+25%) (ps<0.05). Similar proportions of MHC isoforms were evident in the soleus muscles of both strains (ps>0.05); however, for the BLAJ EDL, there was an increased proportion of type IIx MHC isoform (+5.5%) and decreased type IIb isoform (-5.5%) (ps<0.01). This identification of novel differences in the impact of dysferlin-deficiency on slow and fast twitch muscles emphasises the importance of evaluating myofibre type specific effects to provide crucial insight into the mechanisms responsible for loss of function in dysferlinopathies; this is critical for the development of targeted future clinical therapies.

Targeting Complement Pathways in Polytrauma- and Sepsis-Induced Multiple-Organ Dysfunction

Exposure to traumatic or infectious insults results in a rapid activation of the complement cascade as major fluid defense system of innate immunity. The complement system acts as a master alarm system during the molecular danger response after trauma and significantly contributes to the clearance of DAMPs and PAMPs. However, depending on the origin and extent of the damaged macro- and micro -milieu, the complement system can also be either excessively activated or inhibited. In both cases, this can lead to a maladaptive immune response and subsequent multiple cellular and organ dysfunction. The arsenal of complement-specific drugs offers promising strategies for various critical conditions after trauma, hemorrhagic shock, sepsis, and multiple organ failure. The imbalanced immune response needs to be detected in a rational and real-time manner before the translational therapeutic potential of these drugs can be fully utilized. Overall, the temporal-spatial complement response after tissue trauma and during sepsis remains somewhat enigmatic and demands a clinical triad: reliable tissue damage assessment, complement activation monitoring, and potent complement targeting to highly specific rebalance the fluid phase innate immune response.

Changes in the Lectin Pathway Following Intracerebral or Spontaneous Subarachnoid Hemorrhage

Previous research indicates that the complement system is activated after occurrence of intracerebral hemorrhage (ICH) and spontaneous subarachnoid hemorrhage (SAH). The role of the lectin pathway (LP) of the complement system in this activation has only scarcely been investigated. The aim of this study was to determine the plasma concentration of the LP proteins in patients with ICH or SAH at admission compared to healthy individuals. Secondly, ICH and SAH patients were followed during the initial 24 h of disease, to investigate changes in LP protein concentrations during the critical acute phase. This prospective, observational study included 30 ICH and 33 SAH patients. EDTA plasma samples were collected at admission, 6 and 24 h after symptom onset. Time-resolved immuno-flourometric assays (TRIFMA) were used to measure all proteins of the LP in patient samples and in samples from age- and gender-matched healthy individuals. Compared to healthy individuals, ICH and SAH patients had increased levels of H-ficolin (p = 0.04, p = 0.03), M-ficolin (both p < 0.0001), and MAp44 (both p = 0.01) at admission. M-ficolin, H-ficolin, CL-L1, MASP-1, MASP-3, and MAp44 decreased significantly in both ICH and SAH patients during the initial 24 h after symptom onset. In conclusion, we observed significant differences in lectin pathway protein concentrations between patients with ICH or SAH and healthy individuals. Significant dynamics in lectin pathway protein levels were demonstrated during the initial 24 h after symptom onset. This indicates a potential role of the LP proteins during the acute phase of SAH and ICH.

Ficolin-1 Levels in Patients Developing Vasospasm and Cerebral Ischemia After Spontaneous Subarachnoid Hemorrhage

Activation of the inflammatory generating complement system might play a pathogenic role in spontaneous subarachnoid hemorrhage (SAH). We studied whether plasma and cerebrospinal fluid (CSF) levels of complement proteins were associated with angiographic vasospasm and cerebral ischemic lesions after SAH. Ficolin-1 (M-ficolin), ficolin-3 (H-ficolin), mannose-binding lectin (MBL), MBL-associated serine protease 2 (MASP-2), MASP-3, and MAp44 were analyzed in plasma of 45 SAH patients at 24 h after bleeding. Additionally, ficolin-1 levels were measured in cerebrospinal fluid (CSF) samples obtained 24 h after bleeding in 19 patients with external ventricular drainage placement. Angiographic vasospasm was identified using transcranial Doppler or angio-CT and considered symptomatic when new focal deficits or ischemic lesions appeared in follow-up neuroimaging. Functional outcome was assessed using modified Rankin scale (mRS) at 90 days. Higher plasma ficolin-1 levels (ng/ml) at 24 h were associated with poor Hunt and Hess (HH) grade at admission (mean 1158 (SD 360) vs 1654 (871), p = 0.004) and were higher in patients developing angiographic vasospasm (1119.44 (374) vs 1514 (755), p = 0.025) and cerebral ischemia (1067 (325) vs 1610 (766), p = 0.003). In multivariate models adjusted for confounders, higher ficolin-1 remained associated with brain ischemic lesions (OR per 100 ng/ml 1.34, 95 %CI 1.04-1.73, p = 0.026) and vasospasm (OR per 100 ng/ml of increase 1.26, 95 %CI 1.02-1.56, p = 0.031). Patients with angiographic vasospasm and cerebral ischemic lesions had non-significantly lower ficolin-1 concentration in the CSF. Plasma ficolin-1 emerged as a marker of clinical severity and brain ischemia after SAH. Larger studies will be required to establish the therapeutic implications of this finding.

Effect of hyperbaric oxygen preconditioning on peri-hemorrhagic focal edema and aquaporin-4 expression

The aim of the present study was to investigate the effect of hyperbaric oxygen preconditioning (HBO-PC) on peri-hemorrhagic focal edema and aquaporin-4 (AQP-4) expression in an experimental intracerebral hemorrhage (ICH) rat model. Sixty-six Sprague Dawley® rats were divided into three groups: The sham-surgery group (SHG; n=6); the control group (A-ICH; n=30), in which the rats were injected with autologous blood; and the experimental HBO-PC group (P-HBO; n=30). The rats underwent brain edema and AQP-4 detection at 5 postoperative time-points (24, 48 and 72 h and 5 and 7 days). The water content in the brain tissues of the A-ICH animals was higher than that in the brain tissues of the SHG rats at each time-point (P<0.05), and the edema in the P-HBO was significantly more severe 24 and 48 h postoperatively than that at 7 days postoperatively (P<0.05). The difference between the P-HBO and A-ICH was significant at 48 and 72 h postoperatively (P<0.05). AQP-4 was expressed in the post-hemorrhagic rat brains of all groups; the SHG animals exhibited low expression, while the A-ICH animals exhibited an increased expression 24 h postoperatively. In the A-ICH, expression peaked at 48 h postoperatively and began to decrease gradually after 72 h. At the 7-day time-point, the expression level in the A-ICH was closer to but still higher than that of the SHG animals (P<0.05). The differences between the P-HBO and A-ICH animals at the postoperative 24-h, 48-h and 7-day time-points were statistically significant (P<0.05). In conclusion, HBO-PC may downregulate AQP-4 expression to reduce the intracerebral edema, thus strengthening tolerance to ICH and protecting the nerves.

Inflammation, vasospasm, and brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) can lead to devastating neurological outcomes, and there are few pharmacologic treatments available for treating this condition. Both animal and human studies provide evidence of inflammation being a driving force behind the pathology of SAH, leading to both direct brain injury and vasospasm, which in turn leads to ischemic brain injury. Several inflammatory mediators that are elevated after SAH have been studied in detail. While there is promising data indicating that blocking these factors might benefit patients after SAH, there has been little success in clinical trials. One of the key factors that complicates clinical trials of SAH is the variability of the initial injury and subsequent inflammatory response. It is likely that both genetic and environmental factors contribute to the variability of patients' post-SAH inflammatory response and that this confounds trials of anti-inflammatory therapies. Additionally, systemic inflammation from other conditions that affect patients with SAH could contribute to brain injury and vasospasm after SAH. Continuing work on biomarkers of inflammation after SAH may lead to development of patient-specific anti-inflammatory therapies to improve outcome after SAH.