Cancer cell-intrinsic XBP1 drives immunosuppressive reprogramming of intratumoral myeloid cells by promoting cholesterol production.

A hostile microenvironment in tumor tissues disrupts endoplasmic reticulum homeostasis and induces the unfolded protein response (UPR). A chronic UPR in both cancer cells and tumor-infiltrating leukocytes could facilitate the evasion of immune surveillance. However, how the UPR in cancer cells cripples the anti-tumor immune response is unclear. Here, we demonstrate that, in cancer cells, the UPR component X-box binding protein 1 (XBP1) favors the synthesis and secretion of cholesterol, which activates myeloid-derived suppressor cells (MDSCs) and causes immunosuppression. Cholesterol is delivered in the form of small extracellular vesicles and internalized by MDSCs through macropinocytosis. Genetic or pharmacological depletion of XBP1 or reducing the tumor cholesterol content remarkably decreases MDSC abundance and triggers robust anti-tumor responses. Thus, our data unravel the cell-non-autonomous role of XBP1/cholesterol signaling in the regulation of tumor growth and suggest its inhibition as a useful strategy for improving the efficacy of cancer immunotherapy.

Trimethylamine N-oxide exacerbates acetaminophen-induced liver injury by interfering with macrophage-mediated liver regeneration.

Acetaminophen (APAP)-induced acute liver injury (AILI) is the most frequent cause of acute liver failure in developed countries. Trimethylamine N-oxide (TMAO) is a metabolite derived from the gut microbiota and is relatively high in the circulation of the elderly, individuals with diabetes, and heart disease. Herein, we showed that TMAO exacerbates APAP hepatotoxicity. It is possible that delayed liver repair and regeneration that resulted from reduced macrophage accumulation was responsible for this combined hepatotoxicity. Moreover, matrix metalloproteinase 12 (Mmp12), expressed predominantly by macrophages, were reduced by TMAO in vitro and in vivo. This led to the inhibition of macrophage migration and a subsequent decrease in the recruitment of proresolving macrophages to the necrosis area. Furthermore, the administration of recombinant Mmp12 mitigated the enhanced hepatotoxicity in mice cotreated with TMAO and APAP. Overall, this study indicates that TMAO exacerbates APAP-induced hepatotoxicity by hindering macrophage-mediated liver repair, which might stem from the inhibition of Mmp12. These findings imply that liver damage in patients with high levels of circulating TMAO may be more severe in AILI and should exercise caution when treating with NAC.

Cyanidin-3-glucoside attenuates 4-hydroxynonenal- and visible light-induced retinal damage in vitro and in vivo.

4-Hydroxynonenal (HNE) is a highly reactive end-product of lipid peroxidation reaction that leads to retinal pigment epithelial (RPE) cell damage. Cyanidin-3-glucoside (C3G), the most abundant anthocyanin in the edible parts of plants, is a nutritional supplement used for preventing retinal damage. However, the protective effect of C3G against HNE-induced RPE cell damage remains to be elucidated. The protective mechanisms of C3G on ARPE-19 cells after HNE exposure were investigated in this study. Results showed that compared with HNE-treated cells, the viability of ARPE-19 cells was significantly (P < 0.05) increased after 1 and 5 µM C3G treatment. C3G exhibited a significant (P < 0.05) inhibitory effect on the expression of senescence-associated ß-galactosidase in ARPE-19 cells. VEGF levels in the C3G groups were significantly (P < 0.05) decreased relative to those of the HNE-treated group. C3G also regulated the release of two inflammatory mediators, namely monocyte chemoattractant protein 1 and interleukine-8, in ARPE-19 cells after HNE treatment. Furthermore, C3G attenuated retinal cell apoptosis in pigmented rabbits induced by visible light. Therefore, our data showed that C3G has efficient protective effects on HNE-induced apoptosis, angiogenesis, and dysregulated cytokine production in ARPE-19 cells.

Mechanisms of acetaminophen-induced liver injury and its implications for therapeutic interventions.

Acetaminophen (APAP) overdose is the leading cause of drug-induced acute liver failure in many developed countries. Mitochondrial oxidative stress is considered to be the predominant cellular event in APAP-induced liver injury. Accordingly, N-acetyl cysteine, a known scavenger of reactive oxygen species (ROS), is recommended as an effective clinical antidote against APAP-induced acute liver injury (AILI) when it is given at an early phase; however, the narrow therapeutic window limits its use. Hence, the development of novel therapeutic approaches that can offer broadly protective effects against AILI is clearly needed. To this end, it is necessary to better understand the mechanisms of APAP hepatotoxicity. Up to now, in addition to mitochondrial oxidative stress, many other cellular processes, including phase I/phase II metabolism, endoplasmic reticulum stress, autophagy, sterile inflammation, microcirculatory dysfunction, and liver regeneration, have been identified to be involved in the pathogenesis of AILI, providing new targets for developing more effective therapeutic interventions against APAP-induced liver injury. In this review, we summarize intracellular and extracellular events involved in APAP hepatotoxicity, along with emphatic discussions on the possible therapeutic approaches targeting these different cellular events.

Protective role of p53 in acetaminophen hepatotoxicity.

p53 is a tumor suppressor with a pro-death role in many conditions. However, in some contexts, evidence supports a pro-survival function. p53 has been shown to be activated in acetaminophen (APAP) toxicity but the impact of this on toxicity is uncertain. In the present study, we have found that p53 plays a protective role in APAP-induced liver injury. We inhibited p53 using three different approaches in mice, pifithrin-α (PFTα), knockdown of p53 expression with antisense oligonucleotide, and p53 knockout. Mice were treated with APAP (300mg/kg) i.p. and after 24h in all three conditions, the liver injury was more severe as reflected in higher ALT levels and great area of necrosis in histology of the liver. Conversely, a p53 activator, nutlin-3a, decreased the liver injury induced by APAP. In the p53 inhibition models, enhanced sustained JNK activation was seen in the early time course, while the JNK was suppressed with the p53 activator. In conclusion, p53 plays a novel protective role in APAP induced liver injury through inhibiting the activation of JNK, a key mediator in APAP-induced oxidative stress.

Antcin H Protects Against Acute Liver Injury Through Disruption of the Interaction of c-Jun-N-Terminal Kinase with Mitochondria.

AIM: Antrodia Camphorate (AC) is a mushroom that is widely used in Asian countries to prevent and treat various diseases, including liver diseases. However, the active ingredients that contribute to the biological functions remain elusive. The purpose of the present study is to test the hepatoprotective effect of Antcin H, a major triterpenoid chemical isolated from AC, in murine models of acute liver injury. RESULTS: We found that Antcin H pretreatment protected against liver injury in both acetaminophen (APAP) and galactosamine/tumor necrosis factor (TNF)α models. More importantly, Antcin H also offered a significant protection against acetaminophen-induced liver injury when it was given 1 h after acetaminophen. The protection was verified in primary mouse hepatocytes. Antcin H prevented sustained c-Jun-N-terminal kinase (JNK) activation in both models. We excluded an effect of Antcin H on acetaminophen metabolism and TNF receptor signaling and excluded a direct effect as a free radical scavenger or JNK inhibitor. Since the sustained JNK activation through its interaction with mitochondrial Sab, leading to increased mitochondrial reactive oxygen species (ROS), is pivotal in both models, we examined the effect of Antcin H on p-JNK binding to mitochondria and impairment of mitochondrial respiration. Antcin H inhibited the direct effect of p-JNK on isolated mitochondrial function and binding to isolated mitochondria. Innovation and Conclusion: Our study has identified Antcin H as a novel active ingredient that contributes to the hepatoprotective effect of AC, and Antcin H protects against liver injury through disruption of the binding of p-JNK to Sab, which interferes with the ROS-dependent self-sustaining activation of MAPK cascade. Antioxid. Redox Signal. 26, 207-220.

Protective Effect of Proanthocyanidins from Sea Buckthorn (Hippophae Rhamnoides L.) Seed against Visible Light-Induced Retinal Degeneration in Vivo.

Dietary proanthocyanidins (PACs) as health-protective agents have become an important area of human nutrition research because of their potent bioactivities. We investigated the retinoprotective effects of PACs from sea buckthorn (Hippophae rhamnoides L.) seed against visible light-induced retinal degeneration in vivo. Pigmented rabbits were orally administered sea buckthorn seed PACs (50 and 100 mg/kg/day) for 14 consecutive days of pre-illumination and seven consecutive days of post-illumination. Retinal function was quantified via electroretinography 7 days after light exposure. Retinal damage was evaluated by measuring the thickness of the full-thickness retina and outer nuclear layer 7 days after light exposure. Sea buckthorn seed PACs significantly attenuated the destruction of electroretinograms and maintained the retinal structure. Increased retinal photooxidative damage was expressed by the depletion of glutathione peroxidase and catalase activities, the decrease of total antioxidant capacity level and the increase of malondialdehyde level. Light exposure induced a significant increase of inflammatory cytokines (IL-1ß, TNF-α and IL-6) and angiogenesis (VEGF) levels in retina. Light exposure upregulated the expression of pro-apoptotic proteins Bax and caspase-3 and downregulated the expression of anti-apoptotic protein Bcl-2. However, sea buckthorn seed PACs ameliorated these changes induced by light exposure. Sea buckthorn seed PACs mediated the protective effect against light-induced retinal degeneration via antioxidant, anti-inflammatory and antiapoptotic mechanisms.

Cyanidin-3-glucoside and its phenolic acid metabolites attenuate visible light-induced retinal degeneration in vivo via activation of Nrf2/HO-1 pathway and NF-κB suppression.

SCOPE: Cyanidin-3-glucoside (C3G) is a major anthocyanin in berries and a potential nutritional supplement for preventing retinal degeneration. However, the protective mechanism of C3G and its metabolites, protocatechuic acid (PCA) and ferulic acid (FA), remain unclear. The molecular mechanisms of C3G and its metabolites against retinal photooxidative damage in vivo are investigated. METHODS AND RESULTS: Pigmented rabbits were orally administered C3G, PCA, and FA (0.11 mmol/kg/day) for 3 weeks. Electroretinography, histological analysis, and TUNEL assay showed that C3G and its metabolites attenuated retinal cell apoptosis. The expression of oxidative stress markers were upregulated after light exposure but attenuated by C3G and FA, which may be attributed to the elevated secretion and expression of heme oxygenase (HO-1) and nuclear factor erythroid-2 related factor 2 (Nrf2). C3G, PCA, and FA attenuated the secretion or expression of inflammation-related genes; FA suppressed nuclear factor kappa B (NF-κB) activation. The treatments attenuated the light-induced changes on certain apoptotic proteins and angiogenesis-related cytokines. CONCLUSION: C3G and FA reduced light-induced retinal oxidative stress by activating the Nrf2/HO-1 antioxidant pathway. FA attenuated the light-induced retinal inflammation by suppressing NF-κB activation. C3G and its metabolites attenuated the photooxidation-induced apoptosis and angiogenesis in the retina.

Anthocyanin-rich extracts from blackberry, wild blueberry, strawberry, and chokeberry: antioxidant activity and inhibitory effect on oleic acid-induced hepatic steatosis in vitro.

BACKGROUND: Limited information is available regarding the relationship between the chemical structures and inhibitory effects of anthocyanin (ACN) on triglyceride (TG) overaccumulation. Thus this study investigated the antioxidant activity and inhibitory effect of blackberry, wild blueberry, strawberry, and chokeberry ACN-rich extracts, with different structural characteristics, on oleic acid-induced hepatic steatosis in vitro. Four major ACNs from these berries, with different aglycones, namely cyanidin-3-glucoside (Cy-3-glu), delphinidin-3-glucoside, pelargonidin-3-glucoside, and malvidin-3-glucoside, were also investigated. RESULTS: Blackberry ACN-rich extract exhibited the most significant inhibitory effect on TG clearance (30.5% ± 3.4%) and reactive oxygen species generation. TG clearance was significantly correlated with total phenolic content (r = 0.991, P < 0.05) and oxygen radical absorbance capacity value (r = 0.961, P < 0.05). Furthermore, Cy-3-glu showed the highest inhibitory effect on intracellular TG overaccumulation, with a maximum TG clearance of 61.3% at 40 µg mL(-1) . CONCLUSION: Our findings suggest that the inhibitory effects of different ACNs on oleic acid-induced hepatic steatosis significantly vary. Cy-3-glu, which contains the ortho hydroxyl group in its B ring, possibly confers the protective effects of antioxidants and inhibits TG accumulation in HepG2 cells. © 2015 Society of Chemical Industry.

Involvement of ROS-p38-H2AX axis in novel curcumin analogues-induced apoptosis in breast cancer cells.

Curcumin-based structural modification for developing more effective curcumin analogues has been drawning increasing attention. As alternative approach, using LC/MS guided purification, we previously obtained a series of novel natural terpene-conjugated curcuminoids from turmeric, and some of them exhibited even more potent anti-cancer activity against multiple types of cancer cells than curcumin. The purpose of this follow-up study was designed to decipher the mechanisms involved in anti-cancer activity of these novel curcumin analogues. Apoptosis was evaluated using sub-G1 analysis by flow cytometry and Cell Death ELISA Kit. Changes of protein expression were analyzed by western blotting. RNA interference was employed to inhibit expression of specific protein. We found that bisabolocurcumin ether (T1) and demethoxybisabolocurcumin ether (T2) were able to trigger much stronger apoptosis induction in multiple types of cancer cells than curcumin, which was attributed to persistent and stronger ROS generation. ROS induction by T1 resulted in activation of p38/H2AX axis and p53. Inhibition of p38/H2AX led to a significant reduction of apoptosis, whereas inactivation of p53 caused a dramatically enhanced H2AX phosphorylation and apoptosis induction, suggesting activation of p38/H2AX contributed to apoptosis induction by T1, whereas p53 activation protected novel curcumins-induced apoptosis via suppression of H2AX activation. Our findings provide mechanistic support for the potential use of terpene-conjugated curcuminoids as a novel class of cancer chemopreventive agents. © 2015 Wiley Periodicals, Inc.

Glycycoumarin ameliorates alcohol-induced hepatotoxicity via activation of Nrf2 and autophagy.

Licorice, a traditional Chinese medicine, has been used to treat various diseases, including liver disease, for centuries. However, the chemical basis and biological mechanisms underlying the biological functions of licorice remain elusive. The purpose of the current study was to test the hepatoprotective effect of glycycoumarin (GCM), a representative coumarin in licorice, using animal models of both chronic and acute alcoholic liver injury. C57BL/6J mice were used to evaluate the hepatoprotective effect of GCM on liver injury induced by either chronic or acute ethanol exposure. AML-12 and HepG2 cells were utilized to determine the functional role of Nrf2 in the hepatoprotective effect of GCM and to decipher the mechanisms of GCM-induced Nrf2 activation. We found that treatment with GCM leads to a significant reduction in hepatotoxicity in response to either chronic or acute ethanol exposure. Further mechanistic investigations reveal that activation of Nrf2 via the p38 pathway and induction of autophagy by GCM contribute to its hepatoprotective activity. In addition, we demonstrate that p62 upregulation by a transcriptional mechanism also contributes to Nrf2 activation via a positive feedback loop. Our study has identified GCM as a novel active ingredient that contributes to the hepatoprotective activity of licorice.

Involvement of unfolded protein response, p53 and Akt in modulation of porcine reproductive and respiratory syndrome virus-mediated JNK activation.

Our previous study has shown that activation of JNK plays a critical role in Porcine reproductive and respiratory syndrome virus (PRRSV)-mediated apoptosis. In this follow-up study, we further investigated the mechanisms involved in modulation of PRRSV-mediated JNK activation and apoptosis. We found that unfolded protein response (UPR) was induced in response to PRRSV infection which in turn triggered JNK activation and apoptosis. We also found that p53 and Akt were activated at the early stage of infection and functioned as negative regulator of JNK activation to counteract the PRRSV-mediated apoptosis. Furthermore, induction of UPR, p53 and Akt was not only involved in modulation of PRRSV-mediated apoptosis, but also contributed to the virus replication. Our findings indicated that multiple signaling pathways were involved in modulation of PRRSV-mediated apoptosis of the host cells via regulating JNK signaling pathway and provided novel insights into understanding the mechanisms of pathogenesis of PRRSV infection.

Activation of c-Jun NH(2)-terminal kinase is required for porcine reproductive and respiratory syndrome virus-induced apoptosis but not for virus replication.

Apoptosis of host cells plays a critical role in pathogenesis of virus infection. MAPK kinases especially stress-activated protein kinases c-Jun NH(2)-terminal kinase (SAPK/JNK) and p38 are often involved in virus-mediated apoptosis. It has been shown that porcine reproductive and respiratory syndrome virus (PRRSV) infection resulted in apoptosis of the host cells both in vitro and in vivo. The current investigation was initiated to determine whether stress-activated protein kinases JNK and p38 play a role in apoptosis induction by PRRSV infection. We examined phosphorylation of JNK and p38, and found that JNK but not p38 was activated in response to PRRSV infection. We then examined effects of this kinase on apoptosis induction and virus replication by using specific inhibitor. We found that JNK inhibition by its inhibitor SP600125 led to the abolishment of PRRSV-mediated apoptosis, but did not suppress virus replication. Further studies demonstrated that ROS generation was involved in JNK activation, and Bcl-2 family anti-apoptotic proteins Mcl-1 and Bcl-xl were downstream targets of JNK to mediate apoptosis. We conclude that activation of JNK signaling pathway is essential for PRRSV-mediated apoptosis but not for virus replication.