Higenamine reduces HMGB1 during hypoxia-induced brain injury by induction of heme oxygenase-1 through PI3K/Akt/Nrf-2 signal pathways

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Osthole, a natural coumarin improves cognitive impairments and BBB dysfunction after transient global brain ischemia in C57 BL/6J mice: involvement of Nrf2 pathway

Oxidative stress and blood-brain barrier (BBB) disruption play important roles in cerebral ischemic pathogenesis and may represent targets for treatment. Earlier studies have shown that osthole, a main active constituent isolated from Cnidium monnieri (L.) Cusson, could be considered as an attractive therapeutic agent in the treatment of ischemic stroke. However, the mechanism underlying the protective effect remains vague. In this study we aimed to investigate the effect of osthole on transient cerebral ischemia as well as its mechanism(s) in C57 BL/6 J mice. Mice were subjected to transient global cerebral ischemia induced by bilateral common carotid artery occlusion for 25 min. Behavioral test was performed at 4 days after ischemia, followed by assessment of neuronal loss in hippocampal CA1 region. Osthole significantly improved the cognitive ability and enhanced the survival of pyramidal neurons in the CA1 region of mice after lesion. Further studies showed that osthole attenuated the permeation of BBB, which may contribute to antioxidative effect by increasing the superoxide dismutase activity and decreasing the malondialdehyde level in model mice. Further studies revealed that osthole obviously up-regulated the protein levels of nuclear factor erythroid 2-related factor 2/heme oxygenase 1 in HT22 cells. In conclusion, our findings indicated that osthole exerts neuroprotective effects against global cerebral ischemia injury by reducing oxidative stress injury and reserving the disruption of BBB, which may be attributed to elevating the protein levels of Nrf2 and HO-1.

Dehydrocostuslactone inhibits LPS-induced inflammation by p38MAPK-dependent induction of hemeoxygenase-1 in vitro and improves survival of mice in CLP-induced sepsis in vivo

We investigated the hypothesis that the administration of dehydrocostuslactone (DL), a sesquiterpene lactone found in Saussurea lappa Clarke (Compositae), might reduce organ failure and increase survival in a cecal ligation and puncture (CLP)-induced mouse model of sepsis due to HO-1 induction. Treatment of RAW264.7 cells with DL increased HO-1 expression in a time- and concentration-dependent manner, and this up-regulation of HO-1 by DL was significantly inhibited by silencing either Nrf2 and p38 or treating cells with SB203580 (a p38MAPK inhibitor), but it was not inhibited in the presence of SP600125 (an ERK inhibitor), PD98059 (a JNK inhibitor), or LY294002 (PI3K inhibitor). As expected, DL concentration dependently inhibited the expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2), and the productions of NO and PGE2 in LPS-activated cells, and these inhibitions were reversed by silencing HO-1. Most importantly, administration of DL significantly reduced mortality and reduced serum IL-1β and TNF-α and the infiltration of macrophages into liver tissues of CLP-mice. Inducible NOS expression in lung and liver tissues of CLP-mice was reduced by DL, which was reversed by the co-administration of zinc-protoporphyrin IX (ZnPPIX; a competitive inhibitor of HO-1). Our findings indicate that DL might be useful for the treatment of sepsis.

HIF-1α involves in neuronal apoptosis after traumatic brain injury in adult rats

Hypoxia-inducible factor-1α (HIF-1α), a well-identified hypoxia-related protein, is involved in regulating the biological functions of various cell types including neurons. The traditional biological function of HIF-1α is promoting the transcription of some pro-survival genes when exposing to low oxygen conditions. Meanwhile, some studies also point out that HIF-1α shows the detrimental role in several central nervous system (CNS) disorders. Up to now, the knowledge of HIF-1α function in CNS is still limited. To investigate whether HIF-1α is involved in CNS impairment and repair, we employed a traumatic brain injury model in adult rats. Upregulation of HIF-1α was observed in the injured brain cortex by western blot analysis and immunohistochemistry staining. Terminal deoxynucleotidyl transferase deoxy-UTP nick-end labeling (TUNEL) and 4',6-diamidino-2-phenylindole (DAPI) staining suggested that HIF-1α was relevant to neuronal apoptosis after brain injury. In addition, glutamate excitotoxic model of primary cortex neurons was introduced to further investigate the role of HIF-1α in neuronal apoptosis; the result implied HIF-1α was associated with the regulation of p53 and BNIP3 in the apoptotic neurons. Based on our data, we suggested that HIF-1α might play an important role in neuronal apoptosis after traumatic brain injury in rat, which might also provide a basis for the further study on its role in regulating the transcription of target genes in apoptotic neurons, and might gain a novel strategy for the clinical therapy for traumatic brain injury.

Ginsenoside RK3 Prevents Hypoxia-Reoxygenation Induced Apoptosis in H9c2 Cardiomyocytes via AKT and MAPK Pathway

Reperfusion therapy is widely utilized for acute myocardial infarction (AMI), but further injury induced by rapidly initiating reperfusion of the heart is often encountered in clinical practice. Ginsenoside RK3 (RK3) is reportedly present in the processed Radix notoginseng that is often used as a major ingredient of the compound preparation for ischemic heart diseases. This study aimed to investigate the possible protective effect of RK3 against hypoxia-reoxygenation (H/R) induced H9c2 cardiomyocytes damage and its underlying mechanisms. Our results showed that RK3 pretreatment caused increased cell viability and decreased levels of LDH leakage compared with the H/R group. Moreover, RK3 pretreatment inhibited cell apoptosis, as evidenced by decreased caspase-3 activity, TUNEL-positive cells, and Bax expression, as well as increased Bcl-2 level. Further mechanism investigation revealed that RK3 prevented H9c2 cardiomyocytes injury and apoptosis induced by H/R via AKT/Nrf-2/HO-1 and MAPK pathways. These observations indicate that RK3 has the potential to exert cardioprotective effects against H/R injury, which might be of great importance to clinical efficacy for AMI treatment.

Nuclear erythroid 2-related factor 2: a novel potential therapeutic target for liver fibrosis

Hepatic stellate cells (HSC) are the key fibrogenic cells of the liver. HSC activation is a process of cellular transdifferentiation that occurs upon liver injury, but the mechanisms underlying liver fibrosis are unknown. Nuclear erythroid 2-related factor 2 (Nrf2) is an oxidative stress-mediated transcription factor with a variety of downstream targets aimed at cytoprotection. However, Nrf2 has recently been implicated as a new therapeutic target for the treatment of liver fibrosis. This review focuses on the transcriptional repressors that either control liver injury or regulate specific fibrogenic functions of liver fibrosis. We also show that Nrf2 may reveal significant gene expression changes, suggesting that Nrf2 activation may ameliorate liver fibrosis.

Higenamine Combined with [6]-Gingerol Suppresses Doxorubicin-Triggered Oxidative Stress and Apoptosis in Cardiomyocytes via Upregulation of PI3K/Akt Pathway

Sini decoction is a well-known formula of traditional Chinese medicine, which has been used to treat cardiovascular disease for many years. Previously, we demonstrated that Sini decoction prevented doxorubicin-induced heart failure in vivo. However, its active components are still unclear. Thus, we investigated the active components of Sini decoction and their cardioprotective mechanisms in the in vitro neonatal rat cardiomyocytes and H9c2 cell line models of doxorubicin-induced cytotoxicity. Our results demonstrated that treatment with higenamine or [6]-gingerol increased viability of doxorubicine-injured cardiomyocytes. Moreover, combined use of higenamine and [6]-gingerol exerted more profound protective effects than either drug as a single agent, with effects similar to those of dexrazoxane, a clinically approved cardiac protective agent. In addition, we found that treatment with doxorubicin reduced SOD activity, increased ROS generation, enhanced MDA formation, induced release of LDH, and triggered the intrinsic mitochondria-dependent apoptotic pathway in cardiomyocytes, which was inhibited by cotreatment of higenamine and [6]-gingerol. Most importantly, the cytoprotection of higenamine plus [6]-gingerol could be abrogated by LY294002, a PI3K inhibitor. In conclusion, combination of higenamine and [6]-gingerol exerts cardioprotective effect against doxorubicin-induced cardiotoxicity through activating the PI3K/Akt signaling pathway. Higenamine and [6]-gingerol may be the active components of Sini decoction.

The role of HMGB1 in inflammation-mediated organ injury

HMGB1 is a chromosome-binding protein that also acts as a damage-associated molecular pattern molecule. It has potent proinflammatory effects and is one of key mediators of organ injury. Evidence from research has revealed its involvement in the signaling mechanisms of Toll-like receptors and the receptor for advanced glycation end-products in organ injury. HMGB1-mediated organ injuries are acute damage including ischemic, mechanical, allograft rejection and toxicity, and chronic diseases of the heart, kidneys, lungs, and brain. Strategies against HMGB1 and its associated cellular signal pathways need to be developed and may have preventive and therapeutic potentials in organ injury.

Induction of HO-1 through p38 MAPK/Nrf2 signaling pathway by ethanol extract of Inula helenium L. reduces inflammation in LPS-activated RAW 264.7 cells and CLP-induced septic mice

High mobility group box 1 (HMGB1) plays a crucial mediator in the pathogenesis of many inflammatory diseases. We recently proposed that heme oxygenase-1 (HO-1) negatively regulates HMGB1 in inflammatory conditions. We investigated whether ethanol extract of Inula helenium L. (EIH) activates p38 MAPK/Nrf2/HO-1 pathways in RAW264.7 cells and reduces inflammation in CLP-induced septic mice. EIH induced expression of HO-1 protein in a time- and concentration-dependent manner. EIH significantly diminished HO-1 expression in siNrf2 RNA-transfected cells. As expected, the inhibited expression of iNOS/NO, COX-2/PGE2, HMGB1 release by EIH in LPS-activated RAW264.7 cells was significantly reversed by siHO-1RNA transfection. Furthermore, EIH not only inhibited NF-κB luciferase activity, phosphorylation of IκBα in LPS-activated cells but also significantly suppressed expression of adhesion molecules (ICAM-1 and VCAM-1) in TNF-α activated human umbilical vein endothelial cells. The induction of HO-1 by EIH was inhibited by SB203580 but not by SP600125, PD98059, nor LY294002. Most importantly, administration of EIH significantly reduced not only increase in blood HMGB1, ALT, AST, BUN, creatinine levels but also decrease macrophage infiltrate in the liver of septic mice, which were reversed by ZnPPIX, a HO-1 inhibitor. We concluded that EIH has anti-inflammatory effect via the induction of p38 MAPK-dependent HO-1 signaling pathway.

Influence of racemic higenamine on the sinus node

The aim of this study was to explore the mechanism of racemic higenamine in the treatment of sick sinus syndrome (SSS). A total of 40 New Zealand rabbits were randomly divided into normal sinus node and damaged sinus node (SND) groups, and each group was randomly divided into treatment and control groups (n=10). The SND model was established by formaldehyde wet dressing of the sinus node area. The treatment groups were administered an intravenous infusion of 0.04 mg/kg racemic higenamine via the marginal ear vein within 5 min. The electrophysiological indicators of sinoatrial function, including the sinus node recovery time (SNRT), corrected sinus node recovery time (CSNRT), total sinoatrial conduction time (TSACT) and sinus cycle length (SCL), were determined before and 20 min after medication and the changes in these indicators were evaluated. The two control groups were administered 10 ml physiological saline. Following the administration of racemic higenamine, the SNRT, CSNRT, TSACT and SCL in the normal sinus node and SND groups were significantly shortened compared with those in the control groups (P<0.01). The electrophysiological influence of racemic higenamine on sinoatrial function in the SND group was significantly greater than that in the normal sinus node group (P<0.01), and its effect in the treatment of arrhythmia caused by a damaged sinus node was statistically significant (P<0.05). The main electrophysiological mechanism of racemic higenamine in the treatment of SSS was the enhancement of sinus node self-discipline and improvement of sinoatrial and atrioventricular conduction function.