Thrombin-induced, TNFR-dependent miR-181c downregulation promotes MLL1 and NF-κB target gene expression in human microglia.

BACKGROUND: Controlling thrombin-driven microglial activation may serve as a therapeutic target for intracerebral hemorrhage (ICH). Here, we investigated microRNA (miRNA)-based regulation of thrombin-driven microglial activation using an in vitro thrombin toxicity model applied to primary human microglia. METHODS: A miRNA array identified 22 differential miRNA candidates. Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) identified miR-181c as the most significantly downregulated miRNA. TargetScan analysis identified mixed lineage leukemia-1 (MLL1) as a putative gene target for miR-181c. qRT-PCR was applied to assess tumor necrosis factor-alpha (TNF-α), miR-181c, and MLL1 levels following thrombin or proteinase-activated receptor-4-specific activating peptide (PAR4AP) exposure. Anti-TNF-α antibodies and tumor necrosis factor receptor (TNFR) silencing were employed to test TNF-α/TNFR dependence. A dual-luciferase reporter system and miR-181c mimic transfection assessed whether mir-181c directly binds to and negatively regulates MLL1. Nuclear factor kappa-B (NF-κB)-dependent luciferase reporter assays and NF-κB target gene expression were assessed in wild-type (MLL1+) and MLL1-silenced cells. RESULTS: Thrombin or PAR4AP-induced miR-181c downregulation (p < 0.05) and MLL1 upregulation (p < 0.05) that were dependent upon TNF-α/TNFR. miR-181c decreased wild-type MLL1 3'-UTR luciferase reporter activity (p < 0.05), and a miR-181c mimic suppressed MLL1 expression (p < 0.05). Thrombin treatment increased, while miR-181c reduced, NF-κB activity and NF-κB target gene expression in both wild-type (MLL1+) and MLL1-silenced cells (p < 0.05). CONCLUSIONS: Thrombin-induced, TNF-α/TNFR-dependent miR-181c downregulation promotes MLL1 expression, increases NF-κB activity, and upregulates NF-κB target gene expression. As miR-181c opposes thrombin's stimulation of pro-inflammatory NF-κB activity, miR-181c mimic therapy may show promise in controlling thrombin-driven microglial activation following ICH.

Transforming growth factor­ß1 functions as a competitive endogenous RNA that ameliorates intracranial hemorrhage injury by sponging microRNA­93­5p.

Intracerebral hemorrhage (ICH) has the highest mortality rate of all stroke subtypes but an effective treatment has yet to be clinically implemented. Transforming growth factor­ß1 (TGF­ß1) has been reported to modulate microglia­mediated neuroinflammation after ICH and promote functional recovery; however, the underlying mechanisms remain unclear. Non­coding RNAs such as microRNAs (miRNAs) and competitive endogenous RNAs (ceRNAs) have surfaced as critical regulators in human disease. A known miR­93 target, nuclear factor erythroid 2­related factor 2 (Nrf2), has been shown to be neuroprotective after ICH. It was hypothesized that TGF­ß1 functions as a ceRNA that sponges miR­93­5p and thereby ameliorates ICH injury in the brain. Short interfering RNA (siRNA) was used to knock down TGF­ß1 and miR­93 expression was also pharmacologically manipulated to elucidate the mechanistic association between miR­93­5p, Nrf2, and TGF­ß1 in an in vitro model of ICH (thrombin­treated human microglial HMO6 cells). Bioinformatics predictive analyses showed that miR­93­5p could bind to both TGF­ß1 and Nrf2. It was found that neuronal miR­93­5p was dramatically decreased in these HMO6 cells, and similar changes were observed in fresh brain tissue from patients with ICH. Most importantly, luciferase reporter assays were used to demonstrate that miR­93­5p directly targeted Nrf2 to inhibit its expression and the addition of the TGF­ß1 untranslated region restored the levels of Nrf2. Moreover, an miR­93­5p inhibitor increased the expression of TGF­ß1 and Nrf2 and decreased apoptosis. Collectively, these results identified a novel function of TGF­ß1 as a ceRNA that sponges miR­93­5p to increase the expression of neuroprotective Nrf2 and decrease cell death after ICH. The present findings provided evidence to support miR­93­5p as a potential therapeutic target for the treatment of ICH.

Blockage of Drp1 phosphorylation at Ser579 protects neurons against Aß1­42­induced degeneration.

Alzheimer's disease (AD), one of the most common types of chronic neurodegenerative diseases, is pathologically characterized by the formation of amyloid ß (Aß) peptide­containing plaques and neurofibrillary tangles. Among Aß peptides, Aß1­42 induces neuronal toxicity and neurodegeneration. In our previous studies, Cdk5 was found to regulate Aß1­42­induced mitochondrial fission via the phosphorylation of dynamin­related protein 1 (Drp1) at Ser579. However, whether blockage of Drp1 phosphorylation at Ser579 protects neurons against Aß1­42­induced degeneration remains to be elucidated. Thus, the aim the present study was to examine the effect of mutant Drp1­S579A on neurodegeneration and its underlying mechanism. First, the phosphorylation­defect (phospho­defect) mutant, Lenti­Drp1­S579A was constructed. Phospho­defect Drp1­S579A expression was detected in primary cultures of mouse cortical neurons infected with Lenti­Drp1­S579A using western blotting and it was found to successfully attenuate the phosphorylation of endogenous Drp1 at Ser579. In primary neuronal cultures, the neuronal processes were evaluated under microscopy. Treatment with 10 µM Aß1­42 significantly decreased dendritic density and length, spine outgrowth and synapse number. As expected, infection of neurons with Lenti­Drp1­S579A efficiently alleviated the inhibitory effect of Aß1­42 on neurite outgrowth and synapse density. In addition, infection with Lenti­Drp1­S579A abolished the cleavage of caspase­3 and apoptosis in neurons exposed to Aß1­42. Thus, the current data demonstrated that blockage of Drp1 phosphorylation at Ser579 may be an effective strategy to protect neurons against Aß1­42­induced degeneration and apoptosis. These findings underline the therapeutic potential of targeting Drp1 in the treatment of AD.

NEMO-binding domain peptides alleviate perihematomal inflammation injury after experimental intracerebral hemorrhage.

Inflammation aggravates the lethal consequences of intracerebral hemorrhage. Recently, many studies have found that nuclear factor-κB (NF-κB) is a crucial transcription factor that initiates inflammation in the perihematomal region of ICH. NF-κB essential modulator (NEMO)-binding domain (NBD) peptide, a cell-permeable peptide spanning the NBD of IKKα or IKKß, functions as a highly specific inhibitor of NF-κB. This peptide can negatively regulate the NF-κB pathway. The present study aimed to explore the effects and underlying pathomechanisms of NBD peptides after ICH. Striatum infusion of whole blood or saline was performed on C57BL/6 mice (n = 198). Experimental animals were administered NBD or control (mutated) peptides 2 h before or after ICH by intracerebroventricular injection (icv.). NBD peptides significantly inhibited edema formation, ameliorated the neurological deficits, markedly reduced IκBα and p65 phosphorylation, blocked nuclear translocation of p65, and upregulated IκBα expression by NF-κB after ICH induction. Using an in vitro hemin toxicity model, we investigated the effects of NBD peptides on microglial inflammation. We found that NBD peptides suppressed microglia inflammation and lowered the expression of TNF-α and IL-1ß in both in vivo and in vitro experiments. Further experiments were performed in mice and cultured microglia, which treated with NBD peptides in the presence of p65 siRNA confirmed that the specificity of NBD peptides inhibit ICH-induced NF-κB activation. This study demonstrated that NBD peptides exert a neuroprotective role after ICH and might be a potential candidate for a novel therapeutic strategy for ICH.

MiR-21-5p/dual-specificity phosphatase 8 signalling mediates the anti-inflammatory effect of haem oxygenase-1 in aged intracerebral haemorrhage rats.

Intracerebral haemorrhage (ICH) is a severe neurological disorder caused by bleeding within the brain tissue. Inflammation has been implicated in ICH pathogenesis and is a potential therapeutic target for ICH. Haemin, an activator of haem oxygenase-1 (HO-1), rapidly increases HO-1 protein expression and activity and has been shown to distinctly affect anti-inflammatory functions after central nervous system (CNS) injury. However, less is known about the mechanisms that underlie the anti-inflammatory effects of haemin in aged rats post-ICH. Here, we performed microarray analysis to identify miRNAs that respond strongly to HO-1 regulation in ICH rats and found that miR-21-5p induced the most significant change. Using Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment and Gene Ontology (GO) analysis, we focused on dual-specificity phosphatase 8 (DUSP8) from the predicted miR-21-5p targets. Luciferase reporter assays confirmed that miR-21-5p bound directly to DUSP8. MiR-21-5p upregulation in vitro downregulated DUSP8 expression. Importantly, intracerebroventricularly injecting antagomir for miR-21-5p (A-miR-21-5p), which was used to inhibit miR-21-5p in aged ICH rats, significantly reduced the neurological defects, repaired cognitive impairment, alleviated blood-brain barrier (BBB) permeability, inhibited neuronal apoptosis posthaemorrhage and accelerated haematoma absorption. In addition, serum miR-21-5p levels were notably elevated in patients relative to healthy individuals and were correlated with National Institutes of Health Stroke Scale (NIHSS) scores and clinical outcomes. In summary, A-miR-21-5p increased HO-1 expression in cerebral haematomas, thus eliciting the DUSP8-modulated perifocal neuroprotective effect of haemin. MiR-21-5p with haemin therapy may be a potential therapy post-ICH.

Efficacy and safety of programmable shunt valves for hydrocephalus: A meta-analysis.

OBJECTIVES: Shunt implantation is an option in the treatment of hydrocephalus. However, the benefits and adverse effects of programmable shunt valves have not been well assessed. MATERIALS AND METHODS: Randomized controlled trials (RCTs) and observational studies assessing the efficacy and safety of programmable valves (PV) treatment for hydrocephalus were identified from electronic databases (PubMed, EMBASE, and Cochrane library). The meta-analysis was performed with the fixed-effect model or random-effect model according to heterogeneity. RESULTS: Three RCTs and eight observational studies met the inclusion criteria including 2622 subjects. Compared with non-PV, PV treatment did not have a statistically significant effect on one-year shunt survival rate [relative risk (RR), 1.06; 95% confidence interval (CI), 0.84-1.35], Substantial heterogeneity was observed between studies (P = 0.09; I2 = 65%). PV administration significantly reduced revision rate (RR, 0.56; 95% CI, 0.45-0.69; I2 = 29%; P = 0.23) and over- or under-drainage complications rate (RR, 0.55; 95% CI, 0.32-0.96). PV was not associated with increased rates of other adverse events, including overall complications rate, infection rate and catheter-related complications rate. CONCLUSIONS: PV treatment is safe and may reduce the revision rate and over- or under-drainage complication rate, especially in patients aged less than 18 years with hydrocephalus. PV treatment is not associated with decreased overall complication rates in patients with hydrocephalus, but the trial sequential analysis indicate more studies are needed to confirm this result.