Inhibition of the NF-κB pathway and ERK-mediated mitochondrial apoptotic pathway takes part in the mitigative effect of betulinic acid on inflammation and oxidative stress in cyclophosphamide-triggered renal damage of mice

As a conventional immunosuppressive drug, cyclophosphamide (CYP) exhibits strong hepatotoxicity in clinical applications. Betulinic acid (BA) is a natural triterpenoid that protects against liver damage. However, the underlying mechanism has not yet been elucidated. The purpose of this study was to evaluate the ameliorative effects of BA on CYP-induced hepatotoxicity and further clarify the underlying mechanism. BA pretreatment mitigated CYP-induced liver oxidative damage by alleviating histopathological lesions, reducing reactive oxygen species (ROS) accumulation, and restoring the mRNA expression of antioxidant enzymes (Cu-Sod, Mn-Sod, Cat, and Gsh-Px). BA treatment also suppressed CYP-induced oxidative stress by activating the NRF2 pathway and inhibiting the MAPK signaling pathway. Moreover, BA attenuated CYP-triggered hepatic apoptosis by suppressing excessive mitochondrial fission, boosting mitochondrial fusion, and ameliorating pro-apoptotic protein expression (CASP9 and the ratio of BCL-2/BAX) by blocking the oxidative stress-activated mitochondrial apoptotic pathway. Furthermore, PD98059 (an inhibitor of ERK) and/or BA abated CYP-provoked hepatotoxicity by inhibiting the ERK-MAPK and mitochondrial apoptotic pathways, implying that deactivation of the ERK-mediated mitochondrial apoptotic pathway contributed to the hepatoprotective efficacy of BA against CYP-induced oxidative stress. Therefore, BA could be used as a complementary medicine in patients undergoing CYP treatment owing to its hepatoprotective effects.

To investigate the role of mitogen-activated protein kinase (MAPK) and downstream events in cadmium (Cd)-induced neuronal apoptosis executed via the mitochondrial apoptotic pathway, this study used the PC-12 cell line as a neuronal model. The result showed that Cd significantly decreased cell viability and the Bcl-2 / Bax ratio and increased the percentage of apoptotic cells, release of cytochrome c, caspase-3, and poly(ADP-ribose) polymerase cleavage, and nuclear translocation of apoptosis-inducing factor (AIF) and endonuclease G. In addition, exposure to Cd-induced phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK. Inhibition of ERK and JNK, but not p38 MAPK, partially protected the cells from Cd-induced apoptosis. ERK and JNK inhibition also blocked alteration of the Bcl-2 / Bax ratio and cytochrome c release and suppressed caspase-3 and poly(ADP-ribose) polymerase cleavage and AIF and endonuclease G nuclear translocation. Taken together, these data suggest that the ERK- and JNK-mediated mitochondrial apoptotic pathway played an important role in Cd-induced PC12 cells apoptosis.

The role of mitogen-activated protein kinase in cadmium-induced primary rat cerebral cortical neurons apoptosis via a mitochondrial apoptotic pathway

Betulinic acid attenuates T-2 toxin-induced lung injury by activating Nrf2 signaling pathway and inhibiting MAPK/NF-κB signaling pathway

Sprouty2 regulates proliferation and survival of multiple myeloma byinhibiting activation of the ERK1/2 pathway invitro and invivo.

T-2 toxin, which is mainly produced by specific strains of Fusarium in nature, can induce immunotoxicity and oxidative stress, resulting in immune organ dysfunction and apoptosis. Betulinic acid (BA), a pentacyclic triterpenoids from nature plants, has been demonstrated to possess immunomodulating and antioxidative bioactivities. The purpose of the study was to explore the effect of BA on T-2 toxin-challenged spleen oxidative damage and further elucidate the underlying mechanism. We found that BA not only ameliorated the contents of serum total cholesterol (TC) and triglyceride (TG) but also restored the number of lymphocytes in T-2 toxin-induced mice. BA dose-dependently reduced the accumulation of reactive oxygen species (ROS), enhanced superoxide dismutase (SOD) activity, and decreased malondialdehyde (MDA) content, as well as increased the total antioxidant capacity (T-AOC) in the spleen of T-2-toxin-exposed mice. Moreover, BA reduced inflammatory cell infiltration in the spleen, improved the morphology of mitochondria and enriched the number of organelles in splenocytes, and dramatically attenuated T-2 toxin-triggered splenocyte apoptosis. Furthermore, administration of BA alleviated the protein phosphorylation of p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinases (ERK); decreased the protein expression of kelch-like erythroid cell-derived protein with CNC homology [ECH]-associated protein1 (Keap1); and increased the protein expression of nuclear factor erythroid 2 [NF-E2]-related factor (Nrf2) and heme oxygenase-1 (HO-1) in the spleen. These findings demonstrate that BA defends against spleen oxidative damage associated with T-2 toxin injection by decreasing ROS accumulation and activating the Nrf2 signaling pathway, as well as inhibiting the mitogen-activated protein kinase (MAPK) signaling pathway.

Betulinic acid attenuates cyclophosphamide-induced intestinal mucosa injury by inhibiting the NF-κB/MAPK signalling pathways and activating the Nrf2 signalling pathway

It was demonstrated previously that low dietary potassium (K) intake stimulates Src family protein tyrosine kinase (PTK) expression via a superoxide-dependent signaling. This study explored the role of mitogen-activated protein kinase (MAPK) in mediating the effect of superoxide anions on PTK expression and ROMK (Kir 1.1) channel activity. Western blot analysis demonstrated that low K intake significantly increased the phosphorylation of P38 MAPK (P38) and extracellular signal-regulated kinase (ERK) but had no effect on phosphorylation of c-JUN N-terminus kinase in renal cortex and outer medulla. The stimulatory effect of low K intake on P38 and ERK was abolished by treatment of rats with tempol. The possibility that increases in superoxide and related products that are induced by low K intake were responsible for stimulating phosphorylation of P38 and ERK also was supported by the finding that application of H(2)O(2) increased the phosphorylation of ERK and P38 in the cultured mouse collecting duct cells. Simultaneous blocking of ERK and P38 completely abolished the effect of H(2)O(2) on c-Src expression in mouse collecting duct cells. For determination of the role of P38 and ERK in the regulation of ROMK-like small-conductance K (SK) channels, the patch-clamp technique was used to study the effect of inhibiting P38 and ERK on SK channels in the cortical collecting duct from rats that were on a control K diet (1.1%) and on a K-deficient diet for 1 d. Inhibition of ERK, c-JUN N-terminus kinase, or P38 alone had no effect on SK channels. In contrast, simultaneous inhibition of P38 and ERK significantly increased channel activity. The effect of inhibiting MAPK on SK channels was not affected in the presence of herbimycin A, a PTK inhibitor, and was larger in rats that were on a K-deficient diet than in rats that were on a normal-K diet. However, the stimulatory effect of inhibiting ERK and P38 on SK was absent in the cortical collecting duct that was treated with colchicine. It is concluded that low K intake-induced increases in superoxide levels are responsible for stimulation of P38 and ERK and that MAPK inhibit the SK channels by stimulating PTK expression and via a PTK-independent mechanism.

Betulin and betulinic acid have been widely studied for their anticancer activities. However, their further development is limited due to low bioavailability, poor aqueous solubility, and limited intracellular accumulation. In the present study, a triphenylphosphonium cation moiety was linked to betulin and betulinic acid to specifically target them to cancer cell mitochondria. Biological characterization established that uptake of mitochondria-targeted compound 1a in the mitochondria of cancer cells was increased compared to betulin. The mitochondria-targeted derivatives of betulin and betulinic acid showed stronger cytotoxicity than their parent drugs and exhibited more cytotoxic effects in cancer cells than normal cells. The mechanisms may involve the mitochondrial apoptotic pathway, probably caused by the induction of reactive oxygen species production and reducing mitochondrial membrane potential. More importantly, 1a significantly inhibited cancer cell proliferation and migration in an in vivo zebrafish xenograft model. Collectively, these results encourage further study of 1a analogs as anticancer agents.

Adrenocorticotropin Hormone Stimulates Interleukin-18 Expression in Human HaCaT Keratinocytes

In this study, a new lanostane triterpene glycoside (fomitoside-K) having biologically active molecules was isolated from a mushroom Fomitopsis nigra to test its anticancer activity on human oral squamous cell carcinomas (YD-10B). We focused on the effect of fomitoside-K on apoptosis, the mitochondria-mediated death pathway and the accumulation of reactive oxygen species (ROS) in YD-10B cells. Fomitoside-K could induce a dose and time-dependent apoptosis in YD-10B cells as characterized by cell morphology, cell cycle arrest, inhibition of survivin, activation of poly(ADP-ribose) polymerase (PARP), caspase-3, -9 and an increased expression ratio of Bax/Bcl-2. The mitochondria membrane potential loss and cytochrome c (Cyt C) release from mitochondria to cytosol were observed during the induction. Moreover, fomitoside-K caused dose-dependent elevation of intracellular ROS level and increase phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) in YD-10B cells. To further investigate the mechanisms, we examined the effects of ROS scavenger N-acetyl-L-cysteine (NAC) and selective inhibitors for mitogen activated protein kinase (MAPK) pathways on the cell death. The fomitoside-K induced cell death by ROS was significantly inhibited by NAC, ERK (PD98059) and JNK inhibitor (SP600125). In addition, fomitoside-K has a synergistic effect with adriamycin in suppressing the growth of YD-10B cells. These data suggest that fomitoside-K induces apoptosis in YD-10B cells through the ROS-dependent mitochondrial dysfunction pathway and provides a mechanistic framework for further exploring the use of fomitoside-K against the proliferation of human oral cancer.

Oxidative stress links diverse neuropathological conditions that include stroke, Parkinson's disease, and Alzheimer's disease and has been modeled in vitro with various paradigms that lead to neuronal cell death following the increased accumulation of reactive oxygen species. For example, immortalized neurons and immature primary cortical neurons undergo cell death in response to depletion of the antioxidant glutathione, which can be elicited by administration of glutamate at high concentrations. We have demonstrated previously that this glutamate-induced oxidative toxicity requires activation of the mitogen-activated protein kinase member ERK1/2, but the mechanisms by which this activation takes place in oxidatively stressed neurons are still not fully known. In this study, we demonstrate that during oxidative stress, ERK-directed phosphatases of both the serine/threonine- and tyrosine-directed classes are selectively and reversibly inhibited via a mechanism that is dependent upon the oxidation of cysteine thiols. Furthermore, the impact of ERK-directed phosphatases on ERK1/2 activation and oxidative toxicity in neurons was tested in a neuronal cell line and in primary cortical cultures. Overexpression of the highly ERK-specific phosphatase MKP3 and its catalytic mutant, MKP3 C293S, were neuroprotective in transiently transfected HT22 cells and primary neurons. The neuroprotective effect of the MKP3 C293S mutant, which enhances ERK1/2 phosphorylation but blocks its nuclear translocation, demonstrates the necessity for active ERK1/2 nuclear localization for oxidative toxicity in neurons. Together, these data implicate the inhibition of endogenous ERK-directed phosphatases as a mechanism that leads to aberrant ERK1/2 activation and nuclear accumulation during oxidative toxicity in neurons.

We have developed an original vector library that allowed us to exploit the phenomenon of RNA interference but also allowed us to avoid the confounding effects of the interferon response. In the present work, we used our library of small interfering RNA expression vectors to examine the genes involved in apoptosis that was induced by double-stranded RNA. To our surprise, screening of our library revealed two novel double-stranded RNA-induced apoptotic pathways, a JNK/SAPK-mediated mitochondrial pathway and an ERK2-related pathway, both of which appeared to be independent of the serine-threonine protein kinase-dependent caspase pathway. We also found that MST2 and protein kinase Calpha both activated the pro-apoptotic signal mediated by ERK2. The results of our screening analysis suggested the utility of large scale screenings with libraries of small interfering RNA expression vectors.

Augmentation of TNF-induced osteoclast differentiation by inhibition of ERK and activation of p38: Similar intracellular signaling between RANKL- and TNF-induced osteoclast differentiation

Increased macrophage vulnerability is associated with progression of systemic lupus erythematosus. Our previous studies have shown that cystamine, an inhibitor of transglutaminase 2 (TG2), alleviated the apoptosis of hepatocyte and brain cell in lupus-prone mice NZB/W-F1. In present study, we further investigated the effects of cystamine on apoptosis-prone macrophages (APMs) in the lupus mice. Using two-dimensional gel electrophoresis (2-DE) analysis, we found that cystamine induced a differential protein expression pattern of APM as comparing to the PBS control. The protein spots presenting differential level between cystamine and PBS treatment were then identified by peptide-mass fingerprinting (PMF). After bioinformatic analysis, these identified proteins were found involved in mitochondrial apoptotic pathway, oxidative stress, and mitogen-activated protein (MAP) kinase-mediated pathway. Further investigation revealed that cystamine significantly decreased the levels of apoptotic Bax and Apaf-1 and the activity of caspase-3, and increased the levels of anti-apoptotic Bcl-2 in APM. We also found that these apoptotic mediators were up-regulated in a correlation with the progression of lupus severity in NZB/W-F1, which were little affected in BALB/c mice. We also found that the reduced serum glutathione was restored by cystamine in NZB/W-F1. Interestingly, the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in APM and the phagocytic ability was diminished in presence of cystamine. In conclusion, our findings indicate that cystamine significantly inhibited mitochondrial pathway, induced antioxidant proteins, and diminished phosphorylation of extracellular ERK1/2, which may alleviate the apoptosis and the phagocytic ability of APM.