Activated microglia-derived macrophage-like cells exacerbate brain edema after ischemic stroke correlate with astrocytic expression of aquaporin-4 and interleukin-1 alpha release.

Brain edema following brain infarction affects mobility and mortality. The mechanisms underlying this process remain to be elucidated. Animal studies have shown that aquaporin-4 (AQP4) expression in astrocytes increases after stroke, and its deletion significantly reduces brain swelling. Recently, two kinds of cells, resident microglia-derived macrophage-like cells (MG-MΦ) and bone marrow-derived macrophages (BM-MΦ), have been reported to accumulate in the ischemic core and stimulate adjacent astrocytes. Therefore, we hypothesized that these cells play crucial roles in the expression of AQP4 and ultimately lead to exacerbated brain edema. To verify this hypothesis, we investigated the role of MG- or BM-MΦ in brain edema using a rat model of transient middle cerebral artery occlusion and rat astrocyte primary cultures. AQP4 expression significantly increased in the peri-infarct tissue at 3-7 days post-reperfusion (dpr) and in the core tissue at 5 and 7 dpr, which synchronized with the expression of Iba1, Il1a, Tnf, and C1qa mRNA. Interleukin (IL)-1α treatment or coculture with MG- and BM-MΦ increased AQP4 expression in astrocytes, while an IL-1 receptor type I antagonist reduced these effects. Furthermore, aggravated animals exhibited high expression of Aqp4 and Il1a mRNA in the ischemic core at 7 dpr, which led to the exacerbation of brain edema. MG-MΦ signature genes were highly expressed in the ischemic core in aggravated rats, while BM-MΦ signature genes were weakly expressed. These findings suggest that IL-1α produced by MG-MΦ induces astrocytic AQP4 expression in the peri-infarct and ischemic core tissues, thereby exacerbating brain edema. Therefore, the regulation of MG-MΦ may prevent the exacerbation of brain edema.

Molecular mechanisms of Wischnewski spot development on gastric mucosa in fatal hypothermia: an experimental study in rats.

Numerous dark-brown-coloured small spots called "Wischnewski spots" are often observed in the gastric mucosa in the patients dying of hypothermia, but the molecular mechanisms through which they develop remain unclear. We hypothesised that hypothermia may activate the secretion of gastric acid and pepsin, leading to the development of the spots. To investigate this, we performed experiments using organotypic rat gastric tissue slices cultured at 37 °C (control) or 32 °C (cold). Cold loading for 6 h lowered the extracellular pH in the culture medium. The mRNA expression of gastrin, which regulates gastric acid secretion, increased after cold loading for 3 h. Cold loading increased the expression of gastric H+,K+-ATPase pump protein in the apical canalicular membrane and resulted in dynamic morphological changes in parietal cells. Cold loading resulted in an increased abundance of pepsin C protein and an elevated mRNA expression of its precursor progastricsin. Collectively, our findings clarified that cold stress induces acidification by activating gastric H+,K+-ATPase pumps and promoting pepsin C release through inducing progastricsin expression on the gastric mucosa, leading to tiny haemorrhages or erosions of the gastric mucosa that manifest as Wischnewski spots in fatal hypothermia.

The suppression of TRIM21 and the accumulation of IFN-α play crucial roles in the pathogenesis of osteonecrosis of the femoral head.

Osteonecrosis of the femoral head (ONFH), the pathogenesis of which remains unclear, has been observed in autoimmune disease patients treated with corticosteroids. Recently, it has been shown that anti-tripartite motif-containing 21 (TRIM21) autoantibodies, which are often present in patients with systemic lupus erythematosis and Sjögren's syndrome, inhibit the E3 ligase activity of TRIM21. TRIM21 negatively regulates nuclear factor-κB (NF-κB) and interferon regulatory factors (IRFs) 3 and 7, three downstream transcription factors, via toll-like receptor 4 signaling. The aim of this study was to clarify the role of TRIM21 in the pathogenesis of ONFH using an animal model. Male Wistar rats were injected with lipopolysaccharide (LPS) twice and with methylprednisolone (MPSL) or saline three times. N-acetyl cysteine (NAC) was administered either concurrently with MPSL or once daily for the 3 days following the last MPSL injection. The incidence of ONFH in the MPSL group was 23.5%. Co-treatment of NAC and MPSL increased the incidence of ONFH to 55.6%. MPSL treatment decreased the activity of NF-κB in the liver and significantly increased the activity of both IRF3 and IRF7. No significant differences were observed in the activity of any of these three transcription factors between the MPSL and the co-treatment groups. In the femoral head, co-treatment with NAC and MPSL significantly decreased the expression of TRIM21 at 3 h and significantly increased the expression of interferon (IFN)-α at 24 h when compared with the MPSL group. IFN-α is known to induce cell death. These findings suggest that the suppression of TRIM21 in the femoral head causes an accumulation of IFN-α, which in turn leads to the development of ONFH. In conclusion, the suppression of TRIM21 resulting from altered NF-κB and IRF homeostasis accelerates the ONFH in rats treated with corticosteroids following LPS administration.

Ethanol-induced JNK activation suppressed via active Akt in hepatocytes.

Ethanol induces c-Jun N-terminal kinase (JNK) activation leading to cell death in hepatocytes. However, acute alcohol exposure does not induce remarked cell death in hepatocytes. We hypothesized that active Akt may suppress JNK activation. To clarify this point, we evaluated the role of active Akt in JNK activation under treatment with hepatocyte growth factor (HGF) and compared it with ethanol treatment. Primary rat hepatocytes were treated with 10 ng/ml HGF. 10 min after that, 5 microM insulin, an activator of the Akt pathway, and/or 5 microM LY294002, an inhibitor of the pathway, were added. Hepatocytes were treated with 100 mM ethanol and LY294002. HGF treatment increased JNK activities in hepatocytes. This JNK activation was accumulated by addition of LY294002. These finding suggest that active Akt suppresses JNK activation induced by HGF. On the other hand, addition of insulin did not decrease the JNK activity, showing that insulin-induced Akt activation may rather increase JNK activity. Ethanol also induced JNK activation and this JNK activation was enhanced by LY294002 similar to HGF treatment. We found that active Akt suppressed JNK activation induced by ethanol as well as HGF in hepatocytes. JNK activation may be suppressed by prolonged active Akt or basal active Akt, rather than peaked activation of Akt induced by insulin stimulation. Our results suggest that the suppression of JNK by active Akt may prevent cell death in acute alcohol intoxication.