TLR4 signaling induced TLR2 expression in the process of mimic cerebral ischemia/reperfusion in vitro

Mitochondrial protective mechanism of simvastatin protects against amyloid β peptide-induced injury in SH-SY5Y cells

Mitochondrial dysfunction is implicated in the pathology of neuronal damage during Alzheimer's disease (AD). Previous studies suggest that simvastatin (SV) ameliorates amyloid β (Aβ)‑mediated cognitive impairment in AD patients and transgenic mice; however, the mechanisms remain unknown. To investigate the potential mechanisms by which SV protects against AD neurotoxicity, the present study used a series of cellular and molecular assays to analyze the effects of SV in an in vitro model of Aβ1‑42-induced injury. The results demonstrated that SV protected against Aβ1‑42‑induced SH‑SY5Y cell injury by inhibiting the release of cytochrome c from the mitochondria to the cytoplasm, and reducing the production of intracellular reactive oxygen species. In addition, SV downregulated cleaved‑caspase‑3 protein levels, increased the ratio of B cell lymphoma 2 (Bcl-2) to Bcl-2-associated X protein, and increased the protein levels of peroxisome proliferator-activated receptor γ coactivator-1α in the Aβ1‑42‑treated cells. Furthermore, SV increased the mitochondrial membrane potential and adenosine triphosphate levels, and enhanced the cell respiratory function and mitochondrial mass of the cells. In conclusion, the present study revealed that SV protected SH‑SY5Y cells against Aβ1‑42-induced injury through regulating the mitochondrial apoptosis pathway and mitochondrial function.

Toll‑like receptor 4 contributes to acute kidney injury after cardiopulmonary resuscitation in mice

Toll-like receptor 4 (TLR4) activation mediates renal injury in regional ischemia and reperfusion (I/R) models generated by clamping renal pedicles. However, it remains unclear whether TLR4 is causal in the kidney injury following global I/R induced by cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). The present study used wild-type (C3H/HeN) and TLR4-mutant (C3H/HeJ) mice to produce the CA/CPR model. CA was induced by injection of cold KCl and left untreated for different time periods. After resuscitation (72 h), the level of blood urea nitrogen (BUN) and serum creatinine (Scr), as well as histological changes in renal tissue were assessed to evaluate the severity of acute kidney injury (AKI). The expression of TLR4, intercellular adhesion molecule-1 (ICAM-1), myeloperoxidase (MPO) and growth-regulated oncogene-β (GRO-β) in kidney tissues was detected. The results demonstrated that the levels of Scr and BUN increased significantly in C3H/HeN and C3H/HeJ mice after CPR. CPR also resulted in increased expression of TLR4, ICAM-1, GRO-β and MPO in a CA-duration dependent manner. However, there was decreased expression of ICAM-1, GRO-β and MPO in C3H/HeJ mice compared with that in C3H/HeN mice. C3H/HeJ mice were resistant to AKI as demonstrated by the minor changes in renal histology and function following CPR. In conclusion, mice suffered from AKI after successful CPR and severe AKI occurred in mice with prolonged CA duration. TLR4 and its downstream signaling events that promote neutrophil infiltration via ICAM-1 and GRO-β may be important in mediating inflammatory responses to renal injury after CPR.

Upregulated expression of S100A8 in mice brain after focal cerebral ischemia reperfusion

BACKGROUND:

Recent studies have showed that S100A8 has been implicated in the pathobiology of inflammatory disorders, and that cerebral ischemia reperfusion (I/R) rapidly activates inflammation responses via Toll-like receptor 4 (TLR4). This study aimed to explore the expression of S100A8 and the relationship between S100A8 and TLR4 in focal cerebral ischemia reperfusion injury.

METHODS:

C3H/HeJ mice (n=30) and C3H/HeN mice (n=30) were divided randomly into a C3H/HeJ model group (n=18), a C3H/HeJ control group (n=12), a C3H/HeN model group (n=18), and a C3H/HeN control group (n=12). Middle cerebral artery I/R model in mice was produced using a thread embolism method. The brains of the mice were collected after ischemia for 1 hour and reperfusion for 12 hours. Stroke outcome was evaluated by determination of infarct volume and assessment of neurological impairment scores. Brain injury after cerebral I/R was observed by an optical microscope after TTC and HE dyeing. The immunofluorescence technique and real time PCR were used to test the expression level of S100A8 in brain damage.

RESULTS:

Compared with C3H/HeN mice, TLR4-deficient mice (C3H/HeJ) had lower infarct volumes and better outcomes in neurological tests. The levels of S100A8 increased sharply in the brains of mice after I/R injury. In addition, mice that lacked TLR4 (C3H/HeJ) had lower expression of I/R-induced S100A8 than C3H/HeN mice in the model group, indicating that a close relationship might exist between the levels of S100A8 and TLR4.

CONCLUSION:

S100A8 interaction with TLR4 might be involved in brain damage and in inflammation triggered by I/R injury.

Beta amyloid peptide (25-35) leading to inflammation through Toll-like receptors and the anti-inflammatory effect of genistein in BV-2 cells

Genistein, the main soy isoflavone component, has received much attention for its potential multifunction. Here, we reported that in BV-2 cells, genistein significantly inhibited beta amyloid peptides 25-35 (Aβ25-35)-induced inflammatory response. The results indicated that Aβ25-35-stimulated BV-2 cells upregulated Toll-like receptors 2 and 4, Myd88, and IKK gene expression with the increasing expression of IL-6 and decreasing expression of TGF-β and IL-10. Further, inhibiting TLR4 expression with small interfering RNA prevented the inflammatory response induced by Aβ25-35, indicating the key role of TLRs in Aβ-mediated inflammation. Genistein pre-treated BV-2 cells showed less inflammatory response when exposed to Aβ25-35. These results suggested that Aβ induced BV-2 cells inflammation though TLRs and genistein has an anti-inflammatory effect in vitro.

hsp70-dependent antiviral immunity against cytopathic neuronal infection by vesicular stomatitis virus

The major inducible 70-kDa heat shock protein (hsp70) protects against measles virus (MeV) neurovirulence in the mouse that is caused by a cell-associated noncytolytic neuronal infection. Protection is type I interferon (IFN) dependent, and we have established a novel axis of antiviral immunity in which hsp70 is released from virus-infected neurons to induce IFN-β in macrophages. The present work used vesicular stomatitis virus (VSV) to establish the relevance of hsp70-dependent antiviral immunity to fulminant cytopathic neuronal infections. In vitro, hsp70 that was constitutively expressed in mouse neuronal cells caused a modest increase in VSV replication. Infection induced an early extracellular release of hsp70 from viable cells, and the release was progressive, increasing with virus-induced apoptosis and cell lysis. The impact of this VSV-hsp70 interaction on neurovirulence was established in weanling male hsp70 transgenic and nontransgenic mice. Constitutive expression of hsp70 in neurons of transgenic mice enhanced viral clearance from brain and reduced mortality, and it was correlated with enhanced expression of type I IFN mRNA. Nontransgenic mice were also protected against neurovirulence and expressed increased type I IFN mRNA in brain when hsp70 was expressed by a recombinant VSV (rVSV-hsp70), indicating that hsp70 in the virus-infected cell is sufficient for host protection. In vitro data confirmed extracellular release of hsp70 from cells infected with rVSV-hsp70 and also showed that viral replication is not enhanced when hsp70 is expressed in this manner, suggesting that hsp70-mediated protection in vivo is not dependent on stimulatory effects of hsp70 on virus gene expression.