From receptors to stress-activated MAP kinases

Targeting skeletal interoception: a novel mechanistic insight into intervertebral disc degeneration and pain management

Despite being a leading cause of chronic pain and disability, the underlying mechanisms of intervertebral disc (IVD) degeneration (IVDD) remain unclear. Emerging evidence suggests that mechanosensation (the ability of the skeletal system to perceive mechanical and biochemical signals) mediated by abnormal mechanical loading plays a critical role in the regulation of IVD health. This review examines the complex interactions amongIVDs, intraosseous sensory mechanisms, and the central nervous system (CNS), with a particular focus on the roles of pathways such as PGE2/EP4, Wnt/β-catenin, and NF-κB. This review elucidates the manner in which mechanical stress and aberrant signaling disrupt the homeostasis of the nucleus pulposus (NP), cartilaginous endplate (CEP) and annulus fibrosus (AF), thereby driving degeneration and exacerbating pain. Furthermore, targeted therapeutic strategies, including the modulation of skeletal interoception and dynamic mechanical loading, present novel avenues for reversing IVDD progression. By integrating skeletal biology with spinal pathology, this work offers a novel perspective on the pathogenesis of IVDD and identifies promising strategies for clinical intervention. These findings highlight the potential of targeting skeletal interoception to mitigate IVDD and associated pain, paving the way for innovative, mechanism-driven therapies.

Anti-inflammatory Capacity of a Medicinal herb extract, Anemarrhena asphodeloides, on In vivo and In vitro models-induced atopic dermatitis

Anemarrhena asphodeloides (AA) Bunge, a rhizomatous plant from the Liliaceae family, is traditionally utilized to manage inflammatory conditions. Nevertheless, its impact on atopic dermatitis (AD) and the associated molecular pathways have not yet been fully explored. This study explored the therapeutic effects of AA on AD both in vivo, using 2,4-dinitrofluorobenzene-induced NC/Nga mice, and in vitro, with tumor necrosis factor-α/interferon-γ-stimulated HaCaT keratinocytes. Topical application of AA ointment on the dorsal skin notably alleviated AD symptoms and skin lesions, enhanced the dermatitis score, and improved parameters such as the rate of trans-epidermal water loss, epidermal thickness, mast cell infiltration, systemic IgE levels, and cytokine expression. Furthermore, AA treatment significantly reduced serum levels of thymic stromal lymphopoietin (TSLP) and locally suppressed mRNA expression of thymus and activation-regulated chemokine (TARC) along with other relevant cytokines in affected skin. Both in vivo and in vitro applications of AA curtailed TSLP levels by inhibiting the expression of signal transducer and activator of transcription 6, a key regulator of pruritus and an initiator of mitogen-activated protein kinase signaling pathways. Additionally, AA affected the expression of tumor necrosis factor-like weak inducer of apoptosis/fibroblast growth factor-inducible 14, a pathway of interest in the study of cutaneous inflammatory diseases. Collectively, these findings propose that AA holds potential as an effective therapeutic agent for treating AD-induced skin inflammation.

The JNK signaling pathway in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) serves as the underlying pathology for various spinal degenerative conditions and is a primary contributor to low back pain (LBP). Recent studies have revealed a strong correlation between IDD and biological processes such as Programmed Cell Death (PCD), cellular senescence, inflammation, cell proliferation, extracellular matrix (ECM) degradation, and oxidative stress (OS). Of particular interest is the emerging evidence highlighting the significant involvement of the JNK signaling pathway in these fundamental biological processes of IDD. This paper explores the potential mechanisms through the JNK signaling pathway influences IDD in diverse ways. The objective of this article is to offer a fresh perspective and methodology for in-depth investigation into the pathogenesis of IDD by thoroughly examining the interplay between the JNK signaling pathway and IDD. Moreover, this paper summarizes the drugs and natural compounds that alleviate the progression of IDD by regulating the JNK signaling pathway. This paper aims to identify potential therapeutic targets and strategies for IDD treatment, providing valuable insights for clinical application.

Anticancer Effects of α-Pinene in AGS Gastric Cancer Cells

Gastric cancer is the fifth most common cancer globally and the third leading cause of cancer-related mortality. Existing treatment strategies for gastric cancer often present numerous side effects. Consequently, recent studies have shifted toward devising new treatments grounded in safer natural substances. α-Pinene, a natural terpene found in the essential oils of various plants, such as Lavender angustifolia and Satureja myrtifolia, displays antioxidant, antibiotic, and anticancer properties. Yet, its impact on gastric cancer remains unexplored. This research assessed the effects of α-pinene in vitro using a human gastric adenocarcinoma cell-line (AGS) human gastric cancer cells and in vivo via a xenograft mouse model. The survival rate of AGS cells treated with α-pinene was notably lower than that of the control group, as revealed by the 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide assay. This decline in cell viability was linked to apoptosis, as verified by 4',6-diamidino-2-phenylindole and annexin V/propidium iodide staining. The α-pinene-treated group exhibited elevated cleaved-poly (ADP-ribose) polymerase and B cell lymphoma 2 (Bcl-2)-associated X (Bax) levels and reduced Bcl-2 levels compared with the control levels. Moreover, α-pinene triggered the activation of extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 within the mitogen-activated protein kinase (MAPK) pathway. In the xenograft mouse model, α-pinene induced apoptosis through the MAPK pathway, devoid of toxicity. These findings position α-pinene as a promising natural therapeutic for gastric cancer.

Platycodin D induces apoptosis via regulating MAPK pathway and promotes autophagy in colon cancer cell

Platycodin D (PD) is the main component of triterpene saponins found in Platycodi radix. In this study, we observed a decrease in cell viability, an increase in apoptotic bodies, and an increase in the rate of apoptosis. Also, we observed an increase in cleaved PARP and Bax, a decrease in Bcl-2, and p-ERK, and an increase in p-p38 and p-JNK. Furthermore, a change in cell viability and the expression of p-p38, Bax, and Bcl-2 using the p38 inhibitor revealed a decrease in p-p38 and Bax and an increase in Bcl-2 in the inhibitor treatment group. In addition, we observed an increase in vacuole formation through morphological changes and an increase in acidic vesicular organelles (AVOs). We also observed an increase in the expression of beclin 1, LC 3-I, and -II. There was no significant decrease in cell viability in the group treated with 3-MA, but a decrease in cell viability was noted in the group treated with HCQ. HCQ treatment resulted in an increase in Bax and a decrease in Bcl-2. These findings reveal that in HT-29 colon cancer cells, PD induces apoptosis through the MAPK pathway, thereby exerting anticancer effects. Moreover, autophagy caused by PD inhibits apoptosis by protecting the cells.

Ubiquitination and Metabolic Disease

The increasing incidence of metabolic diseases, including obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic fatty liver disease (NAFLD), in the past decade is a serious concern worldwide. Disruption of cellular protein homeostasis has been considered as a crucial contributor to the pathogenesis of metabolic diseases. To maintain protein homeostasis, cells have evolved multiple dynamic and self-regulating quality control processes to adapt new environmental conditions and prevent prolonged damage. Among them, the ubiquitin proteasome system (UPS), the primary proteolytic pathway for degradation of aberrant proteins via ubiquitination, has an essential role in maintaining cellular homeostasis in response to intracellular stress. Correspondingly, accumulating evidences have shown that dysregulation of ubiquitination can aggravate various metabolic derangements in many tissues, including the liver, skeletal muscle, pancreas, and adipose tissue, and is involved in the initiation and progression of diverse metabolic diseases. In this part, we will summarize the role of ubiquitination in the pathogenesis of metabolic diseases, including obesity, T2DM and NAFLD, and discuss its potential as a therapeutic target.

Sesamin attenuates UVA-induced keratinocyte injury via inhibiting ASK-1-JNK/p38 MAPK pathways

BACKGROUND

Ultraviolet (UV) exposure-stimulated reactive oxygen species (ROS) formation in keratinocytes is a crucial factor in skin aging. Phytochemicals have become widely popular for protecting the skin from UV-induced cell injury. Sesamin (SSM) has been shown to play a role in extensive pharmacological activity and exhibit photoprotective effects.

AIM

To assess the protective effect of SSM on UVA-irradiated keratinocytes and determine its potential antiphotoaging effect.

METHODS

HaCaT keratinocytes pretreated with SSM were exposed to UVA radiation at 8 J/cm2 for 10 min. Cell viability and oxidative stress indicators were evaluated using a cell counting kit-8 and lactate dehydrogenase (LDH), malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) assay kits. Apoptosis and intracellular ROS levels were analyzed using annexin V-fluorescein isothiocyanate/propyridine iodide and dichlorodihydrofluorescein diacetate staining, respectively. Protein levels of matrix metalloprotein-1 (MMP-1), MMP-9, Bax/Bcl-2, and mitogen-activated protein kinase (MAPK) pathway proteins, phospho-apoptosis signal-regulating kinase-1 (p-ASK-1)/ASK-1, phospho-c-Jun N-terminal protein kinase (p-JNK)/JNK, and p-p38/p38 were determined using western blotting.

RESULTS

Sesamin showed no cytotoxicity until 160 μmol/L on human keratinocytes. Sesamin pretreatment (20 and 40 μM) reversed the suppressed cell viability, increased LDH release and MDA content, decreased cellular antioxidants GSH and SOD, and elevated intracellular ROS levels, which were induced by UVA irradiation. Additionally, SSM inhibited the expression of Bax, MMP-1, and MMP-9 and stimulated Bcl-2 expression. In terms of the regulatory mechanisms, we demonstrated that SSM inhibits the phosphorylation of ASK-1, JNK, and p38.

CONCLUSION

The results suggest that SSM attenuates UVA-induced keratinocyte injury by inhibiting the ASK-1-JNK/p38 MAPK pathways.

Temperature-induced Artifacts in Tau Phosphorylation: Implications for Reliable Alzheimer's Disease Research

In preclinical research on Alzheimer's disease and related tauopathies, tau phosphorylation analysis is routinely employed in both cellular and animal models. However, recognizing the sensitivity of tau phosphorylation to various extrinsic factors, notably temperature, is vital for experimental accuracy. Hypothermia can trigger tau hyperphosphorylation, while hyperthermia leads to its dephosphorylation. Nevertheless, the rapidity of tau phosphorylation in response to unintentional temperature variations remains unknown. In cell cultures, the most significant temperature change occurs when the cells are removed from the incubator before harvesting, and in animal models, during anesthesia prior to euthanasia. In this study, we investigate the kinetics of tau phosphorylation in N2a and SH-SY5Y neuronal cell lines, as well as in mice exposed to anesthesia. We observed changes in tau phosphorylation within the few seconds upon transferring cell cultures from their 37°C incubator to room temperature conditions. However, cells placed directly on ice post-incubation exhibited negligible phosphorylation changes. In vivo, isoflurane anesthesia rapidly resulted in tau hyperphosphorylation within the few seconds needed to lose the pedal withdrawal reflex in mice. These findings emphasize the critical importance of preventing temperature variation in researches focused on tau. To ensure accurate results, we recommend avoiding anesthesia before euthanasia and promptly placing cells on ice after removal from the incubator. By controlling temperature fluctuations, the reliability and validity of tau phosphorylation studies can be significantly enhanced.

Crosstalk between phytochemicals and inflammatory signaling pathways

Novel bioactive constituents from natural sources are actively being investigated. The phytochemicals in these phenolic compounds are believed to have a variety of beneficial effects on human health. Several phenolic compounds have been found in plants. The antioxidant potential of phenols has been discussed in numerous studies along with their anti-inflammatory effects on pro-inflammatory cytokine, inducible cyclooxygenase-2, and nitric oxide synthase. Through current study, an attempt is made to outline and highlight a wide variety of inflammation-associated signaling pathways that have been modified by several natural compounds. These signaling pathways include nuclear factor-kappa B (NF-кB), activator protein (AP)-1, protein tyrosine kinases (PTKs), mitogen-activated protein kinases (MAPKs), nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factors, tyrosine phosphatidylinositol 3-kinase (PI3K)/AKT, and the ubiquitin-proteasome system. In light of the influence of natural substances on signaling pathways, their impact on the production of inflammatory mediator is highlighted in this review.

Nuclear RAC1 is a modulator of the doxorubicin-induced DNA damage response

Rho GTPases like RAC1 are localized on the inner side of the outer cell membrane where they act as molecular switches that can trigger signal transduction pathways in response to various extracellular stimuli. Nuclear functions of RAC1 were identified that are related to mitosis, cell cycle arrest and apoptosis. Previously, we showed that RAC1 plays a role in the doxorubicin (Dox)-induced DNA damage response (DDR). In this context it is still unknown whether cytosolic RAC1 modulates the Dox-induced DDR or if a nuclear fraction of RAC1 is involved. Here, we silenced RAC1 in mouse embryonic fibroblasts (MEF) pharmacologically with EHT1864 or by using siRNA against Rac1. Additionally, we transfected MEF with RAC1 mutants (wild-type, dominant-negative, constitutively active) containing a nuclear localization sequence (NLS). Afterwards, we analysed the Dox-induced DDR by evaluation of fluorescent nuclear γH2AX and 53BP1 foci formation, as well as by detection of activated proteins of the DDR by western blot to elucidate the role of nuclear RAC1 in the DDR. Treatment with EHT1864 as well as Rac1 knock-down reduced the Dox-induced DSB-formation to a similar extent. Enhanced nuclear localization of dominant-negative as well as constitutively active RAC1 mimicked these effects. Expression of the RAC1 mutants altered the Dox-induced amount of pP53 and pKAP1 protein. The observed effects were independent of S1981 ATM phosphorylation. We conclude that RAC1 is required for a substantial activation of the Dox-induced DDR and balanced levels of active/inactive RAC1 inside the nucleus are a prerequisite for this response.

Phosphoproteomics identifies pathways underlying the role of receptor-interaction protein kinase 3 in alcohol-associated liver disease and uncovers apoptosis signal-regulating kinase 1 as a target

Receptor-interaction protein kinase 3 (RIP3), a critical determinant of the necroptotic pathway of programmed cell death, contributes to injury in murine models of alcohol-associated liver disease (ALD); however, the underlying mechanisms are unknown. We investigated the effect of chronic ethanol feeding on the hepatic phosphoproteome in C57BL/6 and RIP3-deficient (Rip3^-/- ) mice, focusing on death receptor (DR) signaling pathways. C57BL/6 and Rip3^-/- mice were fed an ethanol-containing liquid diet or pair-fed control diet. A label-free mass spectrometry-based approach identified differentially phosphorylated proteins that were mapped to pathways affected by ethanol and Rip3 genotype. Identified targets were validated in both the murine model of ALD and in liver tissue from patients with alcohol-associated hepatitis (AH) and healthy controls. Chronic ethanol dysregulated hepatic tumor necrosis factor-induced DR signaling pathways. Of particular importance, chronic ethanol feeding to C57BL/6 mice decreased the phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) at serine (S)1036/S1040 (S1029/S1033 human), sites linked with the inhibition of ASK1 death-promoting activity. This decrease in phosphorylation of inhibitory sites was muted in Rip3^-/- mice. Decreased phosphorylation at S1033 was also lower in liver of patients with severe AH compared to healthy controls, and phosphorylation at the ASK1 activation site (threonine [Thr]-838) was increased in patients with AH. The net impact of these changes in phosphorylation of ASK1 was associated with increased phosphorylation of p38, a downstream target of ASK1, in patients with AH and C57BL/6 but not Rip3^-/- mice. Similarly, chronic ethanol feeding affected the c-Jun N-terminal kinase pathway in C57BL/6 but not Rip3^-/- mice. Taken together, our data indicate that changes in inhibitory phosphorylation of ASK1 are an important target in ALD and suggest the involvement of noncanonical functions of Rip3 in ALD.

Alcohol and HIV-Derived Hepatocyte Apoptotic Bodies Induce Hepatic Stellate Cell Activation

Recently, we found that both HIV and acetaldehyde, an alcohol metabolite, induce hepatocyte apoptosis, resulting in the release of large extracellular vesicles called apoptotic bodies (ABs). The engulfment of these hepatocyte ABs by hepatic stellate cells (HSC) leads to their profibrotic activation. This study aims to establish the mechanisms of HSC activation after engulfment of ABs from acetaldehyde and HIV-exposed hepatocytes (ABAGS+HIV). In vitro experiments were performed on Huh7.5-CYP (RLW) cells to generate hepatocyte ABs and LX2 cells were used as HSC. To generate ABs, RLW cells were pretreated for 24 h with acetaldehyde, then exposed overnight to HIV1ADA and to acetaldehyde for 96 h. Thereafter, ABs were isolated from cell suspension by a differential centrifugation method and incubated with LX2 cells (3:1 ratio) for profibrotic genes and protein analyses. We found that HSC internalized ABs via the tyrosine kinase receptor, Axl. While the HIV gag RNA/HIV proteins accumulated in ABs elicited no productive infection in LX2 and immune cells, they triggered ROS and IL6 generation, which, in turn, activated profibrotic genes via the JNK-ERK1/2 and JAK-STAT3 pathways. Similarly, ongoing profibrotic activation was observed in immunodeficient NSG mice fed ethanol and injected with HIV-derived RLW ABs. We conclude that HSC activation by hepatocyte ABAGS+HIV engulfment is mediated by ROS-dependent JNK-ERK1/2 and IL6 triggering of JAK-STAT3 pathways. This can partially explain the mechanisms of liver fibrosis development frequently observed among alcohol abusing PLWH.

Quercetin induces tongue squamous cell carcinoma cell apoptosis via the JNK activation-regulated ERK/GSK-3α/β-mediated mitochondria-dependent apoptotic signaling pathway

Tongue squamous cell carcinoma (SCC) is a most common type of oral cancer. Due to its highly invasive nature and poor survival rate, the development of effective pharmacological therapeutic agents is urgently required. Quercetin (3,3',4',5,7-pentahydroxyflavone) is a polyphenolic flavonoid found in plants and is an active component of Chinese herbal medicine. The present study investigated the pharmacological effects and possible mechanisms of quercetin on apoptosis of the tongue SCC-derived SAS cell line. Following treatment with quercetin, cell viability was assessed via the MTT assay. Apoptotic and necrotic cells, mitochondrial transmembrane potential and caspase-3/7 activity were analyzed via flow cytometric analyses. A caspase-3 activity assay kit was used to detect the expression of caspase-3 activity. Western blot analysis was performed to examine the expression levels of proteins associated with the MAPKs, AMPKα, GSK3-α/β and caspase-related signaling pathways. The results revealed that quercetin induced morphological alterations and decreased the viability of SAS cells. Quercetin also increased apoptosis-related Annexin V-FITC fluorescence and caspase-3 activity, and induced mitochondria-dependent apoptotic signals, including a decrease in mitochondrial transmembrane potential and Bcl-2 protein expression, and an increase in cytosolic cytochrome c, Bax, Bak, cleaved caspase-3, cleaved caspase-7 and cleaved poly (ADP-ribose) polymerase protein expression. Furthermore, quercetin significantly increased the protein expression levels of phosphorylated (p)-ERK, p-JNK1/2 and p-GSK3-α/β, but not p-p38 or p-AMPKα in SAS cells. Pretreatment with the pharmacological JNK inhibitor SP600125 effectively reduced the quercetin-induced apoptosis-related signals, as well as p-ERK1/2 and p-GSK3-α/β protein expression. Both ERK1/2 and GSK3-α/β inhibitors, PD98059 and LiCl, respectively, could significantly prevent the quercetin-induced phosphorylation of ERK1/2 and GSK3-α/β, but not JNK activation. Taken together, these results suggested that quercetin may induce tongue SCC cell apoptosis via the JNK-activation-regulated ERK1/2 and GSK3-α/β-mediated mitochondria-dependent apoptotic signaling pathway.

CSC-3436 sensitizes triple negative breast cancer cells to TRAIL-induced apoptosis through ROS-mediated p38/CHOP/death receptor 5 signaling pathways

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) shows little or no toxicity in most normal cells and preferentially induces apoptosis in a variety of malignant cells. However, patients develop resistance to TRAIL, therefore, sensitizing agents that can sensitize the tumor cells to TRAIL-mediated apoptosis are necessary. In this study, we investigated the effect of 2-(3-hydroxyphenyl)-5-methylnaphthyridin-4-one (CSC-3436), an useful flavonoid, to overcome the TRAIL-resistant triple negative breast cancer (TNBC) cells. We found that CSC-3436 potentiated TRAIL-induced apoptosis in TRAIL-resistant TNBC cells and this correlated with the upregulation of death receptors (DR)-5 and down-regulation of decreased decoy receptor (DcR)-1 expression. When examined for its mechanism, we found that the decreased expression of anti-apoptotic proteins c-FLIPS/L, Bcl-Xl, Bcl-2, Survivin, and XIAP. CSC-3436 would increase the expression of Bax and promoted the cleavage of bid. In addition, the induction of DR5 by CSC-3436 was found to be dependent on the modulation of reactive oxygen species (ROS)/p38/C/EBP-homologous protein (CHOP) signaling pathways. Overall, our results indicated that CSC-3436 could potentiate the apoptotic effects of TRAIL through down-regulation of cell survival proteins and upregulation of DR5 via the ROS-mediated upregulation of CHOP protein.

TNFα and Immune Checkpoint Inhibition: Friend or Foe for Lung Cancer?

Tumor necrosis factor-alpha (TNFα) can bind two distinct receptors (TNFR1/2). The transmembrane form (tmTNFα) preferentially binds to TNFR2. Upon tmTNFα cleavage by the TNF-alpha-converting enzyme (TACE), its soluble (sTNFα) form is released with higher affinity for TNFR1. This assortment empowers TNFα with a plethora of opposing roles in the processes of tumor cell survival (and apoptosis) and anti-tumor immune stimulation (and suppression), in addition to angiogenesis and metastases. Its functions and biomarker potential to predict cancer progression and response to immunotherapy are reviewed here, with a focus on lung cancer. By mining existing sequencing data, we further demonstrate that the expression levels of TNF and TACE are significantly decreased in lung adenocarcinoma patients, while the TNFR1/TNFR2 balance are increased. We conclude that the biomarker potential of TNFα alone will most likely not provide conclusive findings, but that TACE could have a key role along with the delicate balance of sTNFα/tmTNFα as well as TNFR1/TNFR2, hence stressing the importance of more research into the potential of rationalized treatments that combine TNFα pathway modulators with immunotherapy for lung cancer patients.

Role of intracellular signaling pathways and their inhibitors in the treatment of inflammation

Inflammation is not only a defense mechanism of the innate immune system against invaders, but it is also involved in the pathogenesis of many diseases such as atherosclerosis, thrombosis, diabetes, epilepsy, and many neurodegenerative disorders. The World Health Organization (WHO) reports worldwide estimates of people (9.6% in males and 18.0% in females) aged over 60 years, suffering from symptomatic osteoarthritis, and around 339 million suffering from asthma. Other chronic inflammatory diseases, such as ulcerative colitis and Crohn's disease are also highly prevalent. The existing anti-inflammatory agents, both non-steroidal and steroidal, are highly effective; however, their prolonged use is marred by the severity of associated side effects. A holistic approach to ensure patient compliance requires understanding the pathophysiology of inflammation and exploring new targets for drug development. In this regard, various intracellular cell signaling pathways and their signaling molecules have been identified to be associated with inflammation. Therefore, chemical inhibitors of these pathways may be potential candidates for novel anti-inflammatory drug approaches. This review focuses on the anti-inflammatory effect of these inhibitors (for JAK/STAT, MAPK, and mTOR pathways) describing their mechanism of action through literature search, current patents, and molecules under clinical trials.

Shikonin inhibits proliferation of melanoma cells by MAPK pathway-mediated induction of apoptosis

Shikonin, a natural product isolated from the roots of Lithospermum erythrorhizon, exhibits pharmacological effects against inflammation, ulcers, infections, and tumors. In the present study, we aimed to investigate the antitumor effects of shikonin on the human melanoma cell line, A375SM, and in an in vivo mouse xenograft model. We examined the anticancer effects of shikonin by in vitro experiments (MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, 4′,6-diamidino-2-phenylindole (DAPI) stain, annexin V/ propidium iodide (PI) stain, and protein analysis of apoptosis and mitogen-activated protein kinase (MAPK) pathways). Further, the anticancer effect in vivo was confirmed through a xenograft model. Our results showed that shikonin inhibited the proliferation of melanoma cells in a dose-dependent manner. In addition, shikonin significantly increased nucleus and chromatin condensation and early/late apoptosis. Shikonin also increased the pro-apoptotic proteins and decreased the anti-apoptotic proteins. Additionally, shikonin was overexpressed in MAPK pathways. Investigation of the effects of shikonin in a mouse xenograft model not only showed decreased A375SM tumor volume but also increased apoptosis as determined by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Furthermore, pathologic changes were not observed in the liver and kidney of mice. Collectively, the study indicated that shikonin inhibited the proliferation of the human melanoma cells by inducing apoptosis, mediated by MAPK pathway and that it is a potential candidate for an anticancer drug against melanoma cancer.

Reactive Oxygen Species: Beyond Their Reactive Behavior

Cellular homeostasis plays a critical role in how an organism will develop and age. Disruption of this fragile equilibrium is often associated with health degradation and ultimately, death. Reactive oxygen species (ROS) have been closely associated with health decline and neurological disorders, such as Alzheimer's disease or Parkinson's disease. ROS were first identified as by-products of the cellular activity, mainly mitochondrial respiration, and their high reactivity is linked to a disruption of macromolecules such as proteins, lipids and DNA. More recent research suggests more complex function of ROS, reaching far beyond the cellular dysfunction. ROS are active actors in most of the signaling cascades involved in cell development, proliferation and survival, constituting important second messengers. In the brain, their impact on neurons and astrocytes has been associated with synaptic plasticity and neuron survival. This review provides an overview of ROS function in cell signaling in the context of aging and degeneration in the brain and guarding the fragile balance between health and disease.

Apigenin induces apoptosis by regulating Akt and MAPK pathways in human melanoma cell A375SM

Apigenin, an aromatic compound, exhibits antioxidant, anti-inflammatory and anti-viral effects. The present study aimed to investigate the effects of apigenin on cell proliferation and apoptosis of human melanoma cells A375P and A375SM. Therefore, melanoma cells were treated with apigenin to determine its anti-proliferative and survival effects, using wound healing and MTT assays. The results revealed that melanoma cell viability was decreased in a dose-dependent manner. Furthermore, chromatin condensation, indicating apoptosis, was significantly increased in a dose-dependent manner, as demonstrated by DAPI staining. In addition, increased apoptosis rate following treatment with apigenin was confirmed by Annexin V-propidium iodide staining. The changes in the expression levels of apoptosis-related proteins in A375P and A375SM melanoma cells were subsequently detected using western blot analysis. The results demonstrated that the protein expression levels of Bcl-2 were decreased, whereas those of Bax, cleaved poly ADP-ribose polymerase, cleaved caspase-9 and p53 were upregulated in a dose-dependent manner in apigenin-treated cells compared with those noted in untreated cells. In addition, in apigenin-treated A375P cells, phosphorylated (p)-p38 was upregulated and p-extracellular signal-regulated kinase (ERK), p-c-Jun N-terminal kinase (JNK) and p-protein kinase B (Akt) were downregulated. However, in A375SM cells, apigenin treatment increased p-ERK and p-JNK and decreased p-p38 and p-Akt protein expression levels. Subsequently, the inhibitory effect of apigenin on tumor growth was investigated in vivo. Tumor volume was significantly reduced in the 25 and 50 mg/kg apigenin-treated groups compared with the control group. Additionally, a TUNEL assay was performed to detect apoptotic cells. Immunohistochemical staining also revealed elevated p-ERK expression in the apigenin-treated group compared with the control group. Overall, the findings of the present study indicated that apigenin attenuated the growth of A375SM melanoma cells by inducing apoptosis via regulating the Akt and mitogen-activated protein kinase signaling pathways.

PERK/NRF2 and autophagy form a resistance mechanism against G9a inhibition in leukemia stem cells

BACKGROUND

The histone methyltransferase G9a has recently been identified as a potential target for epigenetic therapy of acute myeloid leukemia (AML). However, the effect of G9a inhibition on leukemia stem cells (LSCs), which are responsible for AML drug resistance and recurrence, is unclear. In this study, we investigated the underlying mechanisms of the LSC resistance to G9a inhibition.

METHODS

We evaluated the effects of G9a inhibition on the unfolded protein response and autophagy in AML and LSC-like cell lines and in primary CD34+CD38- leukemic blasts from patients with AML and investigated the underlying mechanisms. The effects of treatment on cells were evaluated by flow cytometry, western blotting, confocal microscopy, reactive oxygen species (ROS) production assay.

RESULTS

The G9a inhibitor BIX-01294 effectively induced apoptosis in AML cell lines; however, the effect was limited in KG1 LSC-like cells. BIX-01294 treatment or siRNA-mediated G9a knockdown led to the activation of the PERK/NRF2 pathway and HO-1 upregulation in KG1 cells. Phosphorylation of p38 and intracellular generation of reactive oxygen species (ROS) were suppressed. Pharmacological or siRNA-mediated inhibition of the PERK/NRF2 pathway synergistically enhanced BIX-01294-induced apoptosis, with suppressed HO-1 expression, increased p38 phosphorylation, and elevated ROS generation, indicating that activated PERK/NRF2 signaling suppressed ROS-induced apoptosis in KG1 cells. By contrast, cotreatment of normal hematopoietic stem cells with BIX-01294 and a PERK inhibitor had no significant proapoptotic effect. Additionally, G9a inhibition induced autophagy flux in KG1 cells, while autophagy inhibitors significantly increased the BIX-01294-induced apoptosis. This prosurvival autophagy was not abrogated by PERK/NRF2 inhibition.

CONCLUSIONS

PERK/NRF2 signaling plays a key role in protecting LSCs against ROS-induced apoptosis, thus conferring resistance to G9a inhibitors. Treatment with PERK/NRF2 or autophagy inhibitors could overcome resistance to G9a inhibition and eliminate LSCs, suggesting the potential clinical utility of these unique targeted therapies against AML.

Tamoxifen induces fatty liver disease in breast cancer through the MAPK8/FoxO pathway

BACKGROUND

Prevention of metabolic complications of long-term adjuvant endocrine therapy in breast cancers remained a challenge. We aimed to investigate the molecular mechanism in the development of tamoxifen (TAM)-induced fatty liver in both estrogen receptor (ER)-positive and ER-negative breast cancer.

METHODS AND RESULTS

First, the direct protein targets (DPTs) of TAM were identified using DrugBank5.1.7. We found that mitogen-activated protein kinase 8 (MAPK8) was one DPT of TAM. We identified significant genes in breast cancer and fatty liver disease (FLD) using the MalaCards human disease database. Next, we analyzed the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of those significant genes in breast cancer and FLD using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING). We found that overlapping KEGG pathways in these two diseases were MAPK signaling pathway, Forkhead box O (FoxO) signaling pathway, HIF-1 signaling pathway, AGE-RAGE signaling pathway in diabetic complications, and PI3K-Akt signaling pathway. Furthermore, the KEGG Mapper showed that the MAPK signaling pathway was related to the FoxO signaling pathway. Finally, the functional relevance of breast cancer and TAM-induced FLD was validated by Western blot analysis. We verified that TAM may induce fatty liver in breast cancer through the MAPK8/FoxO signaling pathway.

CONCLUSION

Bioinformatics analysis combined with conventional experiments may improve our understanding of the molecular mechanisms underlying side effects of cancer drugs, thereby making this method a new paradigm for guiding future studies on this issue.

Modification of Cys residues in human thioredoxin-1 by p-benzoquinone causes inhibition of its catalytic activity and activation of the ASK1/p38-MAPK signalling pathway

Quinones can modify biological molecules through both redox-cycling reactions that yield radicals (semiquinone, superoxide and hydroxyl) and via covalent adduction to nucleophiles (e.g. thiols and amines). Kinetic data indicate that Cys residues in GSH and proteins are major targets. In the studies reported here, the interactions of a prototypic quinone compound, p-benzoquinone (BQ), with the key redox protein, thioredoxin-1 (Trx1) were examined. BQ binds covalently with isolated Trx1 forming quinoprotein adducts, resulting in a concentration-dependent loss of enzyme activity and crosslink formation. Mass spectrometry peptide mass mapping data indicate that BQ forms adducts with all of the Trx1 Cys residues. Glutathione (GSH) reacts competitively with BQ, and thereby modulates the loss of activity and crosslink formation. Exposure of macrophage-like (J774A.1) cells to BQ results in a dose-dependent loss of Trx and thioredoxin reductase (TrxR) activities, quinoprotein formation, and a decrease in GSH levels without a concomitant increase in oxidized glutathione. GSH depletion aggravates the loss of Trx and TrxR activity. These data are consistent with adduction of GSH to BQ being a primary protective pathway. Reaction of BQ with Trx in cells resulted in the activation of apoptosis signal-regulating kinase 1 (ASK1), and p38 mitogen-activated protein kinase (MAPK) leading to apoptotic cell death. These data suggest that BQ reacts covalently with Cys residues in Trx, including at the active site, leading to enzyme inactivation and protein cross-linking. Modification of the Cys residues in Trx also results in activation of the ASK1/p38-MAPK signalling pathway and promotion of apoptotic cell death.

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Quinone (e.g. p-benzoquinone, BQ) toxicity is linked to Michael adduction reactions.

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Adduction of BQ to Cys residues in proteins are rapid (≤10⁵ M⁻¹ s⁻¹) and selective.

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BQ reaction with Cys inactivates thioredoxin (Trx) and yields quinone- and disulfide-linked dimers.

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GSH reacts competitively with BQ and modulates damage, without GSSG formation.

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BQ activates ASK1 and p38 pathways and induced apoptosis in cells via Trx damage.

Liver ASK1 protects from non-alcoholic fatty liver disease and fibrosis

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with obesity and may progress to non-alcoholic steatohepatitis (NASH) and liver fibrosis. The deficit of pharmacological therapies for the latter mainly results from an incomplete understanding of involved pathological mechanisms. Herein, we identify apoptosis signal-regulating kinase 1 (ASK1) as a suppressor of NASH and fibrosis formation. High-fat diet-fed and aged chow-fed liver-specific ASK1-knockout mice develop a higher degree of hepatic steatosis, inflammation, and fibrosis compared to controls. In addition, pharmacological inhibition of ASK1 increased hepatic lipid accumulation in wild-type mice. In line, liver-specific ASK1 overexpression protected mice from the development of high-fat diet-induced hepatic steatosis and carbon tetrachloride-induced fibrosis. Mechanistically, ASK1 depletion blunts autophagy, thereby enhancing lipid droplet accumulation and liver fibrosis. In human livers of lean and obese subjects, ASK1 expression correlated negatively with liver fat content and NASH scores, but positively with markers for autophagy. Taken together, ASK1 may be a novel therapeutic target to tackle NAFLD and liver fibrosis.

Contrast Induced Acute Kidney Injury and Direct Cytotoxicity of Iodinated Radiocontrast Media on Renal Proximal Tubule Cells

The administration of intravenous iodinated radiocontrast media (RCM) to visualize internal structures during diagnostic procedures has increased exponentially since their first use in 1928. A serious side effect of RCM exposure is contrast-induced acute kidney injury (CI-AKI), which is defined as an abrupt and prolonged decline in renal function occurring 48-72 hours after injection. Multiple attempts have been made to decrease the toxicity of RCM by altering ionic strength and osmolarity, yet there is little evidence to substantiate that a specific RCM is superior in avoiding CI-AKI. RCM-associated kidney dysfunction is largely attributed to alterations in renal hemodynamics, specifically renal vasoconstriction; however, numerous studies indicate direct cytotoxicity as a source of epithelial damage. Exposure of in vitro renal proximal tubule cells to RCM has been shown to affect proximal tubule epithelium in the following manner: 1) changes to cellular morphology in the form of vacuolization; 2) increased production of reactive oxygen species, resulting in oxidative stress; 3) mitochondrial dysfunction, resulting in decreased efficiency of the electron transport chain and ATP production; 4) perturbation of the protein folding capacity of the endoplasmic reticulum (ER) (activating the unfolded protein response and inducing ER stress); and 5) decreased activity of cell survival kinases. The present review focuses on the direct cytotoxicity of RCM on proximal tubule cells in the absence of in vivo complications, such as alterations in renal hemodynamics or cytokine influence.

Inhibition of epidermal growth factor receptor improves antitumor efficacy of vemurafenib in BRAF-mutant human melanoma in preclinical model

Oncogenic activation of the epidermal growth factor receptor (EGFR) signaling pathway occurs in a variety of tumor types, albeit in human melanoma, the contribution of EGFR is still unclear. The potential role of EGFR was analyzed in four BRAF-mutant, one NRAS-mutant and one wild-type NRAS-BRAF-carrying human melanoma cell lines. We have tested clinically available reversible tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib, irreversible EGFR-TKI pelitinib and a reversible experimental compound PD153035 on in-vitro proliferation, apoptosis, migration as well as in-vivo metastatic colonization in a spleen-liver model. The presence of the intracellular domain of EGFR protein and its constitutive activity were demonstrated in all cell lines. Efficacies of EGFR-TKIs showed significant differences, and irreversible inhibition had the strongest antitumor potential. Compared with BRAF-mutant cells, wild-type BRAF was associated with relative resistance against gefitinib. In combination with gefitinib, selective mutant BRAF-inhibitor vemurafenib showed additive effect in all BRAF-mutant cell lines. Treatment of BRAF-mutant cells with gefitinib or pelitinib attenuated in-vitro cell migration and in-vivo colonization. Our preclinical data suggest that EGFR is a potential target in the therapy of BRAF-mutant malignant melanoma; however, more benefits could be expected from irreversible EGFR-TKIs and combined treatment settings.

Codelivery of Plasmid and Curcumin with Mesoporous Silica Nanoparticles for Promoting Neurite Outgrowth

Reactive oxygen species (ROS)-induced oxidative stress leads to neuron damage and is involved in the pathogenesis of chronic inflammation in neurodegenerative diseases (NDs), such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis. Researchers, therefore, are looking for antiinflammatory drugs and gene therapy approaches to slow down or even prevent neurological disorders. Combining therapeutics has shown a synergistic effect in the treatment of human diseases. Many nanocarriers could be designed for the simultaneous codelivery of drugs with genes to fight diseases. However, only a few researches have been performed in NDs. In this study, we developed a mesoporous silica nanoparticle (MSN)-based approach for neurodegenerative therapy. This MSN-based platform involved multiple designs in the targeted codelivery of (1) curcumin, a natural antioxidant product, to protect ROS-induced cell damage and (2) plasmid RhoG-DsRed, which is associated with the formation of lamellipodia and filopodia for promoting neurite outgrowth. At the same time, TAT peptide was introduced to the plasmid RhoG-DsRed via electrostatic interaction to elevate the efficiency of nonendocytic pathways and the nuclear plasmid delivery of RhoG-DsRed in cells for enhanced gene expression. Besides, such a plasmid RhoG-DsRed/TAT complex could work as a noncovalent gatekeeper. The release of curcumin inside the channel of the MSN could be triggered when the complex was dissociated from the MSN surface. Taken together, this MSN-based platform combining genetic and pharmacological manipulations of an actin cytoskeleton as well as oxidative stress provides an attractive way for ND therapy.

Skeletal Muscle Cell Oxidative Stress as a Possible Therapeutic Target in a Denervation-Induced Experimental Sarcopenic Model

STUDY DESIGN

A basic study using a rodent model of sarcopenia.

OBJECTIVE

To elucidate the contribution of oxidative stress to muscle degeneration and the efficacy of antioxidant treatment for sarcopenia using an animal model of neurogenic sarcopenia.

SUMMARY OF BACKGROUND DATA

Oxidative stress has been reported to be involved in a number of pathologies, including musculoskeletal disorders. Its relationship with sarcopenia, one of the potential origins of lower back pain, however, is not yet fully understood.

METHODS

Myoblast cell lines (C2C12) were treated with H2O2, an oxidative stress inducer, and N-acetyl-L-cysteine (NAC), an antioxidant. Apoptotic effects induced by oxidative stress and the antioxidant effects of NAC were assessed by western blotting, immunocytochemistry, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assays. An animal model of sarcopenia was produced via axotomy of the sciatic nerves to induce muscle atrophy. Twenty-four male Sprague-Dawley rats were divided into sham, sham+NAC, axotomy, and axotomy+NAC groups. Rats were provided water only or water containing NAC (1 g/L) for 4 weeks. The gastrocnemius muscle was isolated and stained with hematoxylin and eosin (H&E) 2 weeks after axotomy, from which muscle cells were harvested and protein extracted for evaluation.

RESULTS

Mitogen-activated protein kinases (MAPKs) were significantly activated by H2O2 treatment in C2C12 cells, which was ameliorated by NAC pretreatment. Furthermore, H2O2 induced apoptosis and death of C2C12 cells, which was prevented by NAC pretreatment. The weight of the gastrocnemius muscle was reduced in the axotomy group, which was prevented by NAC administration. Lastly, although muscle specimens from the axotomy group showed greater reductions in muscle fiber, the oral administration of NAC significantly inhibited amyotrophy via antioxidant effects.

CONCLUSION

The current in vitro and in vivo study demonstrated the possible involvement of oxidative stress in sarcopenic pathology. NAC represents a potential anti-sarcopenic drug candidate, preventing amyotrophy and fatty degeneration.

LEVEL OF EVIDENCE

4.

Apoptosis signal-regulating kinase 1 activation by Nox1-derived oxidants is required for TNFα receptor endocytosis

Tumor necrosis factor-α (TNFα) is a proinflammatory cytokine that is closely linked to the development of cardiovascular disease. TNFα activates NADPH oxidase 1 (Nox1) and reactive oxygen species (ROS), including superoxide (O₂^·-), production extracellularly is required for subsequent signaling in vascular smooth muscle cells (VSMCs). Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein kinase kinase kinase that is activated by oxidation of associated thioredoxin. The role of ASK1 in Nox1-mediated signaling by TNFα is poorly defined. We hypothesized that ASK1 is required for TNFα receptor endocytosis and subsequent inflammatory TNFα signaling. We employed a knockdown strategy to explore the role of ASK1 in TNFα signaling in VSMCs. siRNA targeting ASK1 had no effect on TNFα-induced extracellular O₂^·- production. However, siASK1 inhibited receptor endocytosis as well as phosphorylation of two endocytosis-related proteins, dynamin1 and caveolin1. Intracellular O₂^·- production was subsequently reduced, as were other inflammatory signaling steps including NF-κB activation, IL-6 production, inducible nitric oxide synthase and VCAM expression, and VSMC proliferation. Prolonged exposure to TNFα (24 h) increased tumor necrosis factor receptor (TNFR) subtype 1 and 2 expression, and these effects were also attenuated by siASK1. ASK1 coimmunoprecipitated with both Nox1 and the leucine rich repeat containing 8A anion channel, two essential components of the TNFR1 signaling complex. Activation of ASK1 by autophosphorylation at Thr845 occurs following thioredoxin dissociation, and this requires the presence of Nox1. Thus, Nox1 is part of the multiprotein ASK1 signaling complex. In response to TNFα, ASK1 is activated by Nox1-derived oxidants, and this plays a critical role in translating these ROS into a physiologic response in VSMCs. NEW & NOTEWORTHY Apoptosis signal-regulating kinase 1 (ASK1) drives dynamin1 and caveolin1 phosphorylation and TNFα receptor endocytosis. ASK1 modulates TNFα-induced NF-κB activation, survival, and proliferation. ASK1 and NADPH oxidase 1 (Nox1) physically associate in a multiprotein signaling complex. Nox1 is required for TNFα-induced ASK1 activation.

β-Arrestin Based Receptor Signaling Paradigms: Potential Therapeutic Targets for Complex Age-Related Disorders

G protein coupled receptors (GPCRs) were first characterized as signal transducers that elicit downstream effects through modulation of guanine (G) nucleotide-binding proteins. The pharmacotherapeutic exploitation of this signaling paradigm has created a drug-based field covering nearly 50% of the current pharmacopeia. Since the groundbreaking discoveries of the late 1990s to the present day, it is now clear however that GPCRs can also generate productive signaling cascades through the modulation of β-arrestin functionality. β-Arrestins were first thought to only regulate receptor desensitization and internalization - exemplified by the action of visual arrestin with respect to rhodopsin desensitization. Nearly 20 years ago, it was found that rather than controlling GPCR signal termination, productive β-arrestin dependent GPCR signaling paradigms were highly dependent on multi-protein complex formation and generated long-lasting cellular effects, in contrast to G protein signaling which is transient and functions through soluble second messenger systems. β-Arrestin signaling was then first shown to activate mitogen activated protein kinase signaling in a G protein-independent manner and eventually initiate protein transcription - thus controlling expression patterns of downstream proteins. While the possibility of developing β-arrestin biased or functionally selective ligands is now being investigated, no additional research has been performed on its possible contextual specificity in treating age-related disorders. The ability of β-arrestin-dependent signaling to control complex and multidimensional protein expression patterns makes this therapeutic strategy feasible, as treating complex age-related disorders will likely require therapeutics that can exert network-level efficacy profiles. It is our understanding that therapeutically targeting G protein-independent effectors such as β-arrestin will aid in the development of precision medicines with tailored efficacy profiles for disease/age-specific contextualities.

Functional cooperation between HIF-1α and c-Jun in mediating primary and acquired resistance to gefitinib in NSCLC cells with activating mutation of EGFR

OBJECTIVE

Hypoxia-inducible factor 1 (HIF-1) and activator protein 1 (AP-1) are important transcription factors regulating expression of genes involved in cell survival. HIF-1α and c-Jun are key components of HIF-1 and AP-1, respectively, and are regulated by epidermal growth factor receptor (EGFR)-mediated cell signaling and tumor microenvironmental cues. The roles of HIF-1α and c-Jun in development of resistance to EGFR tyrosine kinase inhibitor (TKI) in non-small cell lung cancer (NSCLC) with activating mutation of EGFR have not been explored. In this study, we investigated the roles of HIF-1α and c-Jun in mediating primary and acquired resistance to gefitinib in NSCLC cells with activating mutation of EGFR.

MATERIALS AND METHODS

Changes in HIF-1α protein and in total and phosphorylated c-Jun levels in relation to changes in total and phosphorylated EGFR levels before and after gefitinib treatment were measured using Western blot analysis in NSCLC cells sensitive or resistant to gefitinib. The impact of overexpression of a constitutively expressed HIF-1α (HIF-1α/ΔODD) or a constitutively active c-Jun upstream regulator (SEK1 S220E/T224D mutant) on cell response to gefitinib was also examined. The effect of pharmacological inhibition of SEK1-JNK-c-Jun pathway on cell response to gefitinib was evaluated.

RESULTS

Downregulation of HIF-1α and total and phosphorylated c-Jun levels correlated with cell inhibitory response to gefitinib better than decrease in phosphorylated EGFR did in NSCLC cells with intrinsic or acquired resistance to gefitinib. Overexpression of HIF-1α/ΔODD or SEK1 S220E/T224D mutant conferred resistance to gefitinib. There exists a positive feed-forward regulation loop between HIF-1 and c-Jun. The JNK inhibitor SP600125 sensitized gefitinib-resistant NSCLC cells to gefitinib.

CONCLUSIONS

HIF-1α and c-Jun functionally cooperate in development of resistance to gefitinib in NSCLC cells. The translational value of inhibiting HIF-1α/c-Jun cooperation in overcoming resistance to EGFR TKI treatment of NSCLC cells with activating mutation of EGFR deserves further investigation.

YY1 Upregulates Checkpoint Receptors and Downregulates Type I Cytokines in Exhausted, Chronically Stimulated Human T Cells

T cells infiltrate affected organs in chronic infections and malignancy, but they may fail to eradicate virus-infected cells or tumor because of exhaustion. This report describes a Yin Yang-1 (YY1)-centered mechanism for diverse components that have been correlated with exhaustion. Utilizing an in vitro reconstruction of chronic T cell activation, YY1 is shown to positively regulate the checkpoint receptors PD1, Lag3, and Tim3 and to negatively regulate the type I cytokines interleukin-2 (IL-2) (in collaboration with Ezh2 histone methyltransferase) and interferon gamma (IFN-?). Other tests suggest that IL-2 failure drives a large component of cytotoxic functional decline rather than solely checkpoint receptor-ligand interactions that have been the focus of current anti-exhaustion therapies. Clinical evaluations confirm elevated YY1 and Ezh2 in melanoma tumor-infiltrating lymphocytes and in PD1+ T cells in patients with HIV. Exhaustion is revealed to be an active process as the culmination of repetitive two-signal stimulation in a feedback loop via CD3/CD28?p38MAPK/JNK?YY1? exhaustion.

Inhibitory effects of bee venom on mast cell-mediated allergic inflammatory responses

Although bee venom (BV) is a toxin that causes bee stings to be painful, it has been widely used clinically for the treatment of certain immune‑associated diseases. BV has been used traditionally for the treatment of chronic inflammatory diseases. In this regard, the present study analyzed the effect of BV on the regulation of inflammatory mediator production by mast cells and their allergic inflammatory responses in an animal model. HMC‑1 cells were treated with BV prior to stimulation with phorbol‑12‑myristate 13‑acetate plus calcium ionophore A23187 (PMACI). The production of allergy‑associated pro‑inflammatory mediators was examined, and the underlying mechanisms were investigated. Furthermore, to investigate whether BV exhibits anti‑inflammatory effects associated with anti‑allergic effects in vivo, a compound 48/80‑induced anaphylaxis model was used. BV inhibited histamine release, mRNA expression and production of cytokines in the PMACI‑stimulated HMC‑1 cells. Furthermore, the inhibitory effects of BV on mitogen‑activated protein kinase (MAPK), MAPK kinase, signal transducer and activator of transcription 3 (STAT3) and Akt were demonstrated. The present study also investigated the ability of BV to inhibit compound 48/80‑induced systemic anaphylaxis in vivo. BV protected the mice against compound 48/80‑induced anaphylactic‑associated mortality. Furthermore, BV suppressed the mRNA expression levels of pro‑inflammatory cytokines, and suppressed the activation of MAPK and STAT3 in this model. These results provide novel insights into the possible role of BV as a modulator for mast cell‑mediated allergic inflammatory disorders.

Molecular biology and functional genomics of immune-endocrine interactions in the Japanese eel, Anguilla japonica

Immune-endocrine interactions are an important pathogen resistance mechanism in fish. We review the immune-endocrine interactions in the Japanese eel, Anguilla japonica, with special reference to high throughput gene sequencing. These data may be relevant to the significant decrease in the eel harvest in recent years and will aid in the selection of appropriate disease-resistant strains for aquaculture. More than 1000 sequences that whose expression in elvers responded to air exposure were identified through comprehensive gene expression analysis using next-generation sequencing. These included transcription factors within the MAPK pathway. Significant changes in expression after air exposure were detected by quantitative polymerase chain reaction analysis in many genes related to disease resistance. These factors include innate immune system factors and cytokines that interact with the endocrine system during the stress response. Other applications of immune-endocrine interactions in eel culture are discussed.

Knockdown of the transcript of ERK in the brain modulates hypothalamic neuropeptide-mediated appetite control in amphetamine-treated rats

BACKGROUND AND PURPOSE

Amphetamine is a releaser of dopamine stored in synaptic terminals, which can suppress appetite by changing the expression levels of neuropeptide Y (NPY) and proopiomelanocortin (POMC) in the hypothalamus. This study explored whether ERKs are involved in appetite control mediated by cAMP response element binding protein (CREB), NPY and POMC in amphetamine-treated rats.

EXPERIMENTAL APPROACH

Rats were given amphetamine for 4 days, and changes in feeding behaviour and expression levels of phosphorylated-ERK (pERK), pCREB, NPY and melanocortin MC₃ receptors were examined and compared.

KEY RESULTS

Following amphetamine treatment, food intake, body weight and NPY expression decreased, whereas the expression of pERK, pCREB, MC₃ receptors and pCREB/DNA binding activity increased. In amphetamine-treated rats, both cerebral ERK knockdown and pretreatment with a peripheral dopamine receptor antagonist decreased NPY but increased pERK, pCREB and MC₃ receptor expression. Moreover, the immunofluorescence of hypothalamic pERK increased following amphetamine treatment.

CONCLUSIONS AND IMPLICATIONS

These results suggest that ERK/CREB signalling participates in the effects mediated by dopamine receptor/NPY/POMC on appetite control in rats treated with amphetamine. These findings advance the knowledge on the involvement of ERK/CREB signalling in the reciprocal regulation by NPY and POMC of appetite after amphetamine treatment.

Pterostilbene Enhances TRAIL-Induced Apoptosis through the Induction of Death Receptors and Downregulation of Cell Survival Proteins in TRAIL-Resistance Triple Negative Breast Cancer Cells

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) is nontoxic to normal cells and preferentially cytotoxic to cancer cells. Recent data suggest that malignant breast cancer cells often become resistant to TRAIL. Pterostilbene (PTER), a naturally occurring analogue of resveratrol found in blueberries, is known to induce cancer cells to undergo apoptosis. In the present study, we examined whether PTER affects TRAIL-induced apoptosis and its mechanism in TRAIL-resistant triple negative breast cancer (TNBC) cells. Our data indicated that PTER induced apoptosis (14.68 ± 3.78% for 40 μM PTER vs 1.98 ± 0.25% for control, p < 0.01) in TNBC cells and enhanced TRAIL-induced apoptosis in TRAIL-resistant TNBC cells (18.45 ± 4.65% for 40 μM PTER vs 29.38 ± 6.35% for combination of 40 μM PTER and 100 ng/mL TRAIL, p < 0.01). We demonstrated that PTER induced death receptors DR5 and DR4 as well as decreased decoy receptor DcR-1 and DcR-2 expression. PTER also decreased the antiapoptotic proteins c-FLIPS/L, Bcl-Xl, Bcl-2, survivin, and XIAP. PTER induced the cleavage of bid protein and caused proapoptotic Bax accumulation. Moreover, we found that PTER induced the expression of DR4 and DR5 through the reactive oxygen species (ROS)/ endoplasmic reticulum (ER) stress/ERK 1/2 and p38/C/EBP-homologous protein (CHOP) signaling pathways. Overall, our results showed that PTER potentiated TRAIL-induced apoptosis via ROS-mediated CHOP activation leading to the expression of DR4 and DR5.

Mapping Txnip: Key connexions in progression of diabetic nephropathy

Studies demonstrates the major involvement of inflammatory and apoptotic pathway in the pathophysiology of diabetic nephropathy. The cross talk between inflammatory and apoptotic pathway suggests Txnip as a molecular connexion in progression of disease state. Txnip modulates inflammatory pathway (via ROS production and NLRP3 inflammasome activity) and apoptotic pathway (via mTOR pathway). The key contribution of Txnip in both the pathways, reflects, its crucial role in diabetic nephropathy. In the present review, we have first provided an overview of diabetic nephropathy and Txnip system, followed by the mechanistic insight of Txnip in the progression of diabetic nephropathy. This new mechanistic approach suggests to explore Txnip modulators as a promising therapeutic drug target in diabetic nephropathy.

Insulin in combination with cisplatin induces the apoptosis of ovarian cancer cells via p53 and JNK activation

Drug resistance is an obstacle to effective treatment of ovarian cancer. There have been substantial evidences supporting the association between diabetes and the sensitivity to chemotherapy. Insulin (INS) is believed to be the strongest, most lasting hypoglycemic drug. Therefore, the present study aimed to elucidate whether insulin could facilitate the anti‑proliferative activities of cisplatin (cis‑diamminedichloroplatinum, DDP) in the A2780 ovarian cancer cell line. The inhibitory effects of DPP with/without INS on the growth of A2780 cells was measured by MTT assay. The cell cycle stages and levels of apoptosis were determined by flow cytometry. The amounts of signaling elements involved in the regulation of were examined using western blotting and reverse transcription‑quantitative polymerase chain reaction analysis. The results indicated that INS pre‑treatment enhanced the inhibitory effect of DDP on the proliferation of A2780 cells, and facilitated the apoptosis induced by DDP. INS‑DDP treatment led to a marked decrease in the percentage of G0/G1 phase cells, but a corresponding increase in the proportion of S phase cells. Furthermore, A2780 cells pretreated with INS followed by DDP upregulated the protein expression level of phosphorylated c‑Jun N‑terminal kinase (JNK), which resulted in a substantial increase in the expression levels of p53 mRNA and protein, compared with DDP administration alone. In conclusion, the combination of INS and DDP facilitated the apoptosis of A2780 cells, which may be associated with the activation of the JNK signaling pathway and consequently the involvement of p53 at both mRNA and protein expression levels. These results may be useful in furthering our understanding of the mechanisms involved in the chemotherapeutic treatment of ovarian cancer.

Calcium oxalate crystals induces tight junction disruption in distal renal tubular epithelial cells by activating ROS/Akt/p38 MAPK signaling pathway

Tight junction plays important roles in regulating paracellular transports and maintaining cell polarity. Calcium oxalate monohydrate (COM) crystals, the major crystalline composition of kidney stones, have been demonstrated to be able to cause tight junction disruption to accelerate renal cell injury. However, the cellular signaling involved in COM crystal-induced tight junction disruption remains largely to be investigated. In the present study, we proved that COM crystals induced tight junction disruption by activating ROS/Akt/p38 MAPK pathway. Treating Madin–Darby canine kidney (MDCK) cells with COM crystals induced a substantial increasing of ROS generation and activation of Akt that triggered subsequential activation of ASK1 and p38 mitogen-activated protein kinase (MAPK). Western blot revealed a significantly decreased expression of ZO-1 and occludin, two important structural proteins of tight junction. Besides, redistribution and dissociation of ZO-1 were observed by COM crystals treatment. Inhibition of ROS by N-acetyl-l-cysteine (NAC) attenuated the activation of Akt, ASK1, p38 MAPK, and down-regulation of ZO-1 and occludin. The redistribution and dissociation of ZO-1 were also alleviated by NAC treatment. These results indicated that ROS were involved in the regulation of tight junction disruption induced by COM crystals. In addition, the down-regulation of ZO-1 and occludin, the phosphorylation of ASK1 and p38 MAPK were also attenuated by MK-2206, an inhibitor of Akt kinase, implying Akt was involved in the disruption of tight junction upstream of p38 MAPK. Thus, these results suggested that ROS-Akt-p38 MAPK signaling pathway was activated in COM crystal-induced disruption of tight junction in MDCK cells.

Inflammatory mediator ultra-low-molecular-weight hyaluronan triggers necrosis of B-precursor leukemia cells with high surface CD44 expression

Acute lymphoblastic leukemia (ALL) with mixed lineage leukemia (MLL) gene rearrangements (MLL+ALL) has a dismal prognosis and is characterized by high surface CD44 expression. Known that CD44 has the specific binding sites for a natural ligand hyaluronan (HA), we investigated biological effects of HA with different molecular sizes on MLL+ALL cell lines, and found that the addition of ultra-low-molecular-weight (ULMW)-HA strongly suppressed their thymidine uptakes. The MLL+ALL cell line lacking surface CD44 expression established by genome editing showed no suppression of thymidine uptake. Surface CD44-high B-precursor ALL cell lines other than MLL+, but not T-ALL cell lines, were also suppressed in their thymidine uptakes. The inhibition of thymidine uptakes was because of induction of cell death, but dead cells lacked features of apoptosis on cytospin smears and flow cytometric analysis. The cell death was neither blocked by pan-caspase inhibitor nor autophagy inhibitor, but was completely blocked by necrosis inhibitor necrostatin-1. Necrotic cell death was further supported by a marked release of a high-mobility protein group B1 and morphological changes on transmission electron microscopy. Elevation of intracellular reactive oxygen species production suggested a role for inducing this necrotic cell death. ULMW-HA-triggered cell death was similarly demonstrated in surface CD44-high primary B-precursor leukemia cells. Assuming that ULMW-HA is abundantly secreted at the site of infection and inflammation, this study sheds light on understanding the mechanism of a transient inflammation-associated remission of leukemia. Further, the CD44-targeting may become an effective approach in future for the treatment of refractory B-precursor ALL by its capability of predominantly eradicating CD44-high leukemia-initiating cells.

Moringa oleifera fruit induce apoptosis via reactive oxygen species-dependent activation of mitogen-activated protein kinases in human melanoma A2058 cells

The present study was performed to determine the effect of Moringa oleifera fruit extract on the apoptosis of human melanoma A2058 cells. A2058 cells were treated for 72 h with Moringa oleifera fruit extract at 50-100 µg/ml, and cell viability with apoptotic changes was examined. The involvement of reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) was examined. It was revealed that Moringa oleifera fruit extract significantly inhibited the cell viability and promoted apoptosis of A2058 cells in a concentration-dependent manner. Moringa oleifera fruit extract-treated A2058 cells exhibited increased activities of cleaved caspase-9 and caspase-3. It also caused an enhancement of MAPK phosphorylation and ROS production. The pro-apoptotic activity of Moringa oleifera fruit extract was significantly reversed by pretreatment with the c-Jun N-terminal kinase (JNK) inhibitor SP600125, extracellular-signal-regulated kinase (ERK) inhibitor PD98058 or ROS inhibitor N-acetyl-L-cysteine. Taken together, Moringa oleifera fruit extract is effective in inducing mitochondrial apoptosis of A2058 cells, which is mediated through induction of ROS formation, and JNK and ERK activation. Moringa oleifera fruit extract may thus have therapeutic benefits for human melanoma A2058 cells.

The PARP inhibitor olaparib enhances the cytotoxicity of combined gemcitabine, busulfan and melphalan in lymphoma cells

The combination of gemcitabine (Gem), busulfan (Bu), and melphalan (Mel) is a promising regimen for autologous stem-cell transplantation (SCT) for lymphomas. To further improve the efficacy of [Gem + Bu + Mel], we added poly(ADP-ribose) polymerase (PARP) inhibitor olaparib (Ola). We hypothesized that Ola would inhibit the repair of damaged DNA caused by [Gem + Bu + Mel]. Exposure of J45.01 and Toledo cell lines to IC_10-20 of individual drug inhibited proliferation by 6-16%; [Gem + Bu + Mel] by 20-27%; and [Gem + Bu + Mel + Ola] by 61-67%. The synergistic cytotoxicity of the four-drug combination may be attributed to activation of the DNA-damage response, inhibition of PARP activity and DNA repair, decreased mitochondrial membrane potential, increased production of reactive oxygen species, and activation of the SAPK/JNK stress signaling pathway, all of which may enhance apoptosis. Similar observations were obtained using mononuclear cells isolated from patients with T-cell lymphocytic leukemia. Our results provide a rationale for undertaking clinical trials of this drug combination for lymphoma patients undergoing SCT.

Impacts of Cross-Linkers on Biological Effects of Mesoporous Silica Nanoparticles

Chemically synthesized cross-linkers play decisive roles in variable cargos attached to nanoparticles (NPs). Previous studies reported that surface properties, such as the size, charge, and surface chemistry, are particularly important determinants influencing the biological fate and actions of NPs and cells. Recent studies also focused on the relationship of serum proteins with the surface properties of NPs (also called the protein corona), which is recognized as a key factor in determining the cytotoxicity and biodistribution. However, there is concern that cross-linkers conjugated onto NPs might induce undesirable biological effects. Cell responses induced by cross-linkers have not yet been precisely elucidated. Herein, using mesoporous silica nanoparticles (MSNs) the surfaces of which were separately conjugated with four popular heterobifunctional cross-linkers, i.e., N-[α-maleimidoacetoxy]succinimide ester (AMAS), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), and maleimide poly(ethylene glycol) succinimidyl carboxymethyl ester (MAL-PEG-SCM), we investigated cross-linker-conjugated MSNs to determine whether they can cause cytotoxicity, or enhance reactive oxygen species (ROS) generation, nuclear factor (NF)-κB activation, and p-p38 or p21 protein expressions in RAW264.7 macrophage cells. Furthermore, we also separately conjugated two biomolecules containing TAT peptides and bovine serum albumin (BSA) as model systems to study their cell responses in detail. Finally, in vivo mice studies evaluated the biodistribution and blood assays (biochemistry and complete blood count) of PEG-derivative NPs, and results suggested that TAT peptides caused significant white blood cell (WBC)-related cell and platelet abnormalities, as well as liver and kidney dysfunction compared to BSA when conjugated onto MSNs. The results showed that attention to cross-linkers should be considered an issue in the surface modification of NPs. We anticipate that our results could be helpful in developing biosafety nanomaterials.

Impact on Autophagy and Ultraviolet B Induced Responses of Treatment with the MTOR Inhibitors Rapamycin, Everolimus, Torin 1, and pp242 in Human Keratinocytes

The mechanistic target of Rapamycin (MTOR) protein is a crucial signaling regulator in mammalian cells that is extensively involved in cellular biology. The function of MTOR signaling in keratinocytes remains unclear. In this study, we detected the MTOR signaling and autophagy response in the human keratinocyte cell line HaCaT and human epidermal keratinocytes treated with MTOR inhibitors. Moreover, we detected the impact of MTOR inhibitors on keratinocytes exposed to the common carcinogenic stressors ultraviolet B (UVB) and UVA radiation. As a result, keratinocytes were sensitive to the MTOR inhibitors Rapamycin, everolimus, Torin 1, and pp242, but the regulation of MTOR downstream signaling was distinct. Next, autophagy induction only was observed in HaCaT cells treated with Rapamycin. Furthermore, we found that MTOR signaling was insensitive to UVB but sensitive to UVA radiation. UVB treatment also had no impact on the inhibition of MTOR signaling by MTOR inhibitors. Finally, MTOR inhibition by Rapamycin, everolimus, or pp242 did not affect the series of biological events in keratinocytes exposed to UVB, including the downregulation of BiP and PERK, activation of Histone H2A and JNK, and cleavage of caspase-3 and PARP. Our study demonstrated that MTOR inhibition in keratinocytes cannot always induce autophagy, and the MTOR pathway does not play a central role in the UVB triggered cellular response.

Ask1 regulates murine platelet granule secretion, thromboxane A2 generation, and thrombus formation

Mitogen-activated protein kinases (MAPKs) are expressed in platelets and are activated downstream of physiological agonists. Pharmacological and genetic evidence indicate that MAPKs play a significant role in hemostasis and thrombosis, but it is not well understood how MAPKs are activated upon platelet stimulation. Here, we show that apoptosis signal-regulating kinase 1 (ASK1), a member of the MAP3K family, is expressed in both human and murine platelets. ASK1 is rapidly and robustly activated upon platelet stimulation by physiological agonists. Disruption of Ask1 (Ask1^-/- ) resulted in a marked functional defect in platelets. Ask1^-/- platelets showed an impaired agonist-induced integrin α_IIbβ₃ activation and platelet aggregation. Although there was no difference in Ca²⁺ rise, platelet granule secretion and thromboxane A₂ (TxA₂) generation were significantly attenuated in Ask1^-/- platelets. The defective granule secretion observed in Ask1^-/- platelets was a consequence of impaired TxA₂ generation. Biochemical studies showed that platelet agonists failed to activate p38 MAPK in Ask1^-/- platelets. On the contrary, activation of c-Jun N-terminal kinases and extracellular signal-regulated kinase 1/2 MAPKs was augmented in Ask1^-/- platelets. The defect in p38 MAPK results in failed phosphorylation of cPLA₂ in Ask1^-/- platelets and impaired platelet aggregate formation under flow. The absence of Ask1 renders mice defective in hemostasis as assessed by prolonged tail-bleeding times. Deletion of Ask1 also reduces thrombosis as assessed by delayed vessel occlusion of carotid artery after FeCl₃-induced injury and protects against collagen/epinephrine-induced pulmonary thromboembolism. These results suggest that the platelet Ask1 plays an important role in regulation of hemostasis and thrombosis.

Activin A/Smads signaling pathway negatively regulates Oxygen Glucose Deprivation-induced autophagy via suppression of JNK and p38 MAPK pathways in neuronal PC12 cells

Activin A (Act A), a member of the transforming growth factor-beta (TGF-β), reduces neuronal apoptosis during cerebral ischemia through Act A/Smads signaling pathway. However, little is known about the effect of Act A/Smads pathway on autophagy in neurons. Here, we found that oxygen-glucose deprivation (OGD)-induced autophagy was suppressed by exogenous Act A in a concentration-dependent manner and enhanced by Act A/Smads pathway inhibitor (ActRIIA-Ab) in neuronal PC12 cells. These results indicate that Act A/Smads pathway negatively regulates autophagy in OGD-treated PC12 cells. In addition, we found that c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein (MAP) kinase pathways are involved in the OGD-induced autophagy. The activation of JNK and p38 MAPK pathways in OGD-treated PC12 cells was suppressed by exogenous Act A and enhanced by ActRIIA-Ab. Together, our results suggest that Act A/Smads signaling pathway negatively regulates OGD-induced autophagy via suppression of JNK and p38 MAPK pathways in neuronal PC12 cells.

Lung inflammation caused by inhaled toxicants: a review

Exposure of the lungs to airborne toxicants from different sources in the environment may lead to acute and chronic pulmonary or even systemic inflammation. Cigarette smoke is the leading cause of chronic obstructive pulmonary disease, although wood smoke in urban areas of underdeveloped countries is now recognized as a leading cause of respiratory disease. Mycotoxins from fungal spores pose an occupational risk for respiratory illness and also present a health hazard to those living in damp buildings. Microscopic airborne particulates of asbestos and silica (from building materials) and those of heavy metals (from paint) are additional sources of indoor air pollution that contributes to respiratory illness and is known to cause respiratory illness in experimental animals. Ricin in aerosolized form is a potential bioweapon that is extremely toxic yet relatively easy to produce. Although the aforementioned agents belong to different classes of toxic chemicals, their pathogenicity is similar. They induce the recruitment and activation of macrophages, activation of mitogen-activated protein kinases, inhibition of protein synthesis, and production of interleukin-1 beta. Targeting either macrophages (using nanoparticles) or the production of interleukin-1 beta (using inhibitors against protein kinases, NOD-like receptor protein-3, or P2X7) may potentially be employed to treat these types of lung inflammation without affecting the natural immune response to bacterial infections.