Psoriasin has divergent effects on the innate immune responses of murine glial cells

Pharmacological effects of methysticin and L-sulforaphane through the Nrf2/ARE signaling pathway in MLO-Y4 osteocytes: in vitro study

BACKGROUND

Oxidative stress plays a crucial role in the pathogenesis of many skeletal diseases by inducing osteocyte death. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of various antioxidant gene expressions through antioxidant response element (ARE) against cellular oxidative stress and can be induced by various stimulants, including the phytochemicals methysticin (MET) and L-sulforaphane (SFN). This study aimed to establish an osteocyte in vitro model to investigate the pharmacological effects of MET and SFN on the Nrf2/ARE pathway.

METHODS

MLO-Y4 murine osteocytes and the stably transduced MLO-Y4-SIN-lenti-ARE reporter gene cell line were used. MET and SFN were used as Nrf2 inducers. The cytotoxicity of MET, SFN, and hydrogen peroxide (H2O2) was evaluated using the CytoTox-Glo™ Assay. Time- and dose-dependent ARE induction was examined by Monoluciferase Assay. The mRNA and protein expressions of Nrf2 target markers, such as heme-oxygenase 1 (Ho-1), NADPH quinone dehydrogenase 1 (Nqo1), and thioredoxin reductase 1 (Txnrd1), were detected by RT-qPCR, Western Blot, and immunofluorescence staining, respectively. Osteogenesis markers, osteopontin, and osteocalcin were compared with and without treatment by immunofluorescence staining.

RESULTS

The experimental data showed that MET and SFN induced ARE activity in a time- and dose-dependent manner and increased the mRNA and protein expression of antioxidant markers compared to vehicle-treated controls. The protein expression of osteopontin and osteocalcin in the samples treated with SFN were significantly higher than without treatment, and the number of cell death treated with SFN was significantly lower than without treatment under H2O2-induced stress conditions.

CONCLUSIONS

Nrf2 inducers MET and SFN increased the mRNA expression of antioxidant genes through the Nrf2/ARE pathway in osteocytes. Notably, SFN increased the protein expression of osteocyte-associated osteogenic markers and suppressed cell death under H2O2-induced stress condition. Thus, Nrf2 stimulators can exert stress-relieving and osteogenic effects on osteocytes.

Subarachnoid Hemorrhage Increases Level of Heme Oxygenase-1 and Biliverdin Reductase in the Choroid Plexus

Subarachnoid hemorrhage is a specific, life-threatening form of hemorrhagic stroke linked to high morbidity and mortality. It has been found that the choroid plexus of the brain ventricles forming the blood-cerebrospinal fluid barrier plays an important role in subarachnoid hemorrhage pathophysiology. Heme oxygenase-1 and biliverdin reductase are two of the key enzymes of the hemoglobin degradation cascade. Therefore, the aim of present study was to investigate changes in protein levels of heme oxygenase-1 and biliverdin reductase in the rat choroid plexus after experimental subarachnoid hemorrhage induced by injection of non-heparinized autologous blood to the cisterna magna. Artificial cerebrospinal fluid of the same volume as autologous blood was injected to mimic increased intracranial pressure in control rats. Immunohistochemical and Western blot analyses were used to monitor changes in the of heme oxygenase-1 and biliverdin reductase levels in the rat choroid plexus after induction of subarachnoid hemorrhage or artificial cerebrospinal fluid application for 1, 3, and 7 days. We found increased levels of heme oxygenase-1 and biliverdin reductase protein in the choroid plexus over the entire period following subarachnoid hemorrhage induction. The level of heme oxygenase-1 was the highest early (1 and 3 days) after subarachnoid hemorrhage indicating its importance in hemoglobin degradation. Increased levels of heme oxygenase-1 were also observed in the choroid plexus epithelial cells at all time points after application of artificial cerebrospinal fluid. Biliverdin reductase protein was detected mainly in the choroid plexus epithelial cells, with levels gradually increasing during subarachnoid hemorrhage. Our results suggest that heme oxygenase-1 and biliverdin reductase are involved not only in hemoglobin degradation but probably also in protecting choroid plexus epithelial cells and the blood-cerebrospinal fluid barrier from the negative effects of subarachnoid hemorrhage.

Maggot Extracts Alleviate Inflammation and Oxidative Stress in Acute Experimental Colitis via the Activation of Nrf2

Ulcerative colitis (UC) is a common chronic remitting disease driven through altered immune responses with production of inflammatory cytokines. Oxidant/antioxidant balance is also suggested to be an important factor for the recurrence and progression of UC. Maggots are known as a traditional Chinese medicine also known as "wu gu chong." NF-E2-related factor-2 (Nrf2) transcription factor regulates the oxidative stress response and also represses inflammation. The aim of this study was to investigate the effects of maggot extracts on the amelioration of inflammation and oxidative stress in a mouse model of dextran sulfate sodium- (DSS-) induced colitis and evaluate if the maggot extracts could repress inflammation and oxidative stress using RAW 264.7 macrophages stimulated by lipopolysaccharide (LPS). In the present study, we found that the maggot extracts significantly prevented the loss of body weight and shortening of colon length in UC induced by DSS. Furthermore, DSS-induced expression of proinflammatory cytokines at both mRNA and protein levels in the colon was also attenuated by the maggot extracts. In addition, the maggot extracts could significantly suppress the expression of interleukin- (IL-) 1β, IL-6, TNF-α, NFκB p65, p-IκB, p22-phox, and gp91-phox in LPS-stimulated RAW 264.7 cells and colonic tissues. The maggot extracts increased the level of Nrf2 and prevented the degradation of Nrf2 through downregulating the expression of Keap1, which resulted in augmented levels of HO-1, SOD, and GSH-Px and reduced levels of MPO and MDA. However, after administering an Nrf2 inhibitor (ML385) to block the Nrf2/HO-1 pathway, we failed to observe the protective effects of the maggot extracts in mice with colitis and RAW 264.7 cells. Taken together, our data for the first time confirmed that the maggot extracts ameliorated inflammation and oxidative stress in experimental colitis via modulation of the Nrf2/HO-1 pathway. This study sheds light on the possible development of an effective therapeutic strategy for inflammatory bowel diseases.