Penta-Acetyl Geniposide Induce Apoptosis in C6 Glioma Cells by Modulating the Activation of Neutral Sphingomyelinase-Induced p75 Nerve Growth Factor Receptor and Protein Kinase Cδ Pathway

Mechanisms of Arachidonic Acid In Vitro Tumoricidal Impact

To promote the potential of arachidonic acid (ARA) for cancer prevention and management, experiments were implemented to disclose the mechanisms of its tumoricidal action. Hepatocellular, lung, and breast carcinoma and normal hepatocytes cell lines were exposed to 0 or 50 μM ARA for 30 min and then assessed for proliferative capacity, surface membrane-associated sphingomyelin (SM) content, neutral sphingomyelinase (nSMase) activity, beta 2 microglobulin (β2 m) expression, and ceramide (Cer) levels. Reactive oxygen species (ROS) content and caspase 3/7 activity were evaluated. Exposure to ARA for 30 min led to impairment of the tumor cells' proliferative capacity and revealed that the different cell lines display remarkably similar surface membrane SM content but diverse responses to ARA treatment. Arachidonic acid tumoricidal impact was shown to be associated with nSMase activation, exposure of cell surface membrane β2 m to antibody binding, and hydrolysis of SM to Cer, which accumulated on the cell surface and in the cytosol. The ARA and Cer-mediated inhibition of tumor cell viability appeared to be independent of ROS generation or caspase 3/7 activation. The data were compared and contrasted to findings reported in the literature on ARA tumoricidal mechanisms.

Therapeutic potential of plant iridoids in depression: a review

CONTEXT

Depression is a mental disorder characterized by low mood, reduced interest, impaired cognitive function, and vegetative symptoms such as sleep disturbances or poor appetite. Iridoids are the active constituents in several Chinese classical antidepressant formulae such as Yueju Pill, Zhi-Zi-Hou-Po Decoction, Zhi-Zi-Chi Decoction, and Baihe Dihuang Decoction. Parallel to their wide usages, iridoids are considered potential lead compounds for the treatment of neurological diseases.

OBJECTIVE

The review summarizes the therapeutic potential and molecular mechanisms of iridoids in the prevention or treatment of depression and contributes to identifying research gaps in iridoids as potential antidepressant medication.

METHODS

The following key phrases were sought in PubMed, Google Scholar, Web of Science, and China National Knowledge Internet (CNKI) without time limitation to search all relevant articles with in vivo or in vitro experimental studies as comprehensively as possible: ('iridoid' or 'seciridoid' or 'depression'). This review extracted the experimental data on the therapeutic potential and molecular mechanism of plant-derived iridoids for depression.

RESULTS

Plant iridoids (i.e., catalpol, geniposide, loganin), and secoiridoids (i.e., morroniside, gentiopicroside, oleuropein, swertiamarin), all showed significant improvement effects on depression.

DISCUSSION AND CONCLUSIONS

Iridoids exert antidepressant effects by elevating monoamine neurotransmitters, reducing pro-inflammatory factors, inhibiting hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, increasing brain-derived neurotrophic factor (BDNF) and its receptors, and elevating intestinal microbial abundance. Further detailed studies on the pharmacokinetics, bioavailability, and key molecular targets of iridoids are also required in future research, ultimately to provide improvements to current antidepressant medications.

Nature-Derived Compounds as Potential Bioactive Leads against CDK9-Induced Cancer: Computational and Network Pharmacology Approaches

Given the importance of cyclin-dependent kinases (CDKs) in the maintenance of cell development, gene transcription, and other essential biological operations, CDK blockers have been generated to manage a variety of disorders resulting from CDK irregularities. Furthermore, CDK9 has a crucial role in transcription by regulating short-lived anti-apoptotic genes necessary for cancer cell persistence. Addressing CDK9 with blockers has consequently emerged as a promising treatment for cancer. This study scrutinizes the effectiveness of nature-derived compounds (geniposidic acid, quercetin, geniposide, curcumin, and withanolide C) against CDK9 through computational approaches. A molecular docking study was performed after preparing the protein and the ligands. The selected blockers of the CDK9 exerted reliable binding affinities (−8.114 kcal/mol to −13.908 kcal/mol) against the selected protein, resulting in promising candidates compared to the co-crystallized ligand (LCI). The binding affinity of geniposidic acid (−13.908 kcal/mol) to CDK9 is higher than quercetin (−10.775 kcal/mol), geniposide (−9.969 kcal/mol), curcumin (−9.898 kcal/mol), withanolide C (−8.114 kcal/mol), and the co-crystallized ligand LCI (−11.425 kcal/mol). Therefore, geniposidic acid is a promising inhibitor of CDK9. Moreover, the molecular dynamics studies assessed the structure–function relationships and protein–ligand interactions. The network pharmacology study for the selected ligands demonstrated the auspicious compound–target–pathway signaling pathways vital in developing tumor, tumor cell growth, differentiation, and promoting tumor cell progression. Moreover, this study concluded by analyzing the computational approaches the natural-derived compounds that have potential interacting activities against CDK9 and, therefore, can be considered promising candidates for CKD9-induced cancer. To substantiate this study’s outcomes, in vivo research is recommended.

Targeting the Sphingolipid Rheostat in Gliomas

Gliomas are highly aggressive cancer types that are in urgent need of novel drugs and targeted therapies. Treatment protocols have not improved in over a decade, and glioma patient survival remains among the worst of all cancer types. As a result, cancer metabolism research has served as an innovative approach to identifying novel glioma targets and improving our understanding of brain tumors. Recent research has uncovered a unique metabolic vulnerability in the sphingolipid pathways of gliomas that possess the IDH1 mutation. Sphingolipids are a family of lipid signaling molecules that play a variety of second messenger functions in cellular regulation. The two primary metabolites, sphingosine-1-phosphate (S1P) and ceramide, maintain a rheostat balance and play opposing roles in cell survival and proliferation. Altering the rheostat such that the pro-apoptotic signaling of the ceramides outweighs the pro-survival S1P signaling in glioma cells diminishes the hallmarks of cancer and enhances tumor cell death. Throughout this review, we discuss the sphingolipid pathway and identify the enzymes that can be most effectively targeted to alter the sphingolipid rheostat and enhance apoptosis in gliomas. We discuss each pathway’s steps based on their site of occurrence in the organelles and postulate novel targets that can effectively exploit this vulnerability.

Antidepressant-like effects of penta-acetyl geniposide in chronic unpredictable mild stress-induced depression rat model: Involvement of inhibiting neuroinflammation in prefrontal cortex and regulating hypothalamic-pituitaryadrenal axis

We previously reported that penta-acetyl geniposide ((Ac)₅GP, an acetylated derivative of geniposide) exhibited better pharmacological functions than geniposide, a major active component of Gardenia jasminoides Ellis. This study demonstrated the antidepressant-like effects of (Ac)₅GP and its involved mechanisms using a rat depression model caused by chronic unpredictable mild stress (CUMS). Behavioral tests including sucrose preference, open field and forced swimming were applied to evaluate depression symptoms. IL-1β, IL-6 and TNF-α mRNA and protein levels in prefrontal cortex (PFC) were respectively measured by quantitative PCR and ELISA. The protein levels of IκBα, p-IκBα, NF-κB p65, NLRP3, pro- and mature-IL-1β in PFC were determined by western blot. The activity of hypothalamic-pituitaryadrenal (HPA) axis was also measured. (Ac)₅GP treatment alleviated the CUMS-induced depressive-like behaviors in rats, as indicated by increased sucrose intake, increased total crossing and rearing numbers, improved central activity and reduced immobility time. (Ac)₅GP reversed the CUMS-induced elevations of IL-1β, IL-6 and TNF-α mRNA and protein levels in PFC. (Ac)₅GP reduced degradation and phosphorylation of IκBα and protein level of nuclear NF-κB p65 in PFC. (Ac)₅GP also decreased the mRNA and protein levels of NLRP3 and reduced the ratio of mature-IL-1β protein over total IL-1β protein (pro-IL-1β + mature-IL-1β) in PFC. Moreover, (Ac)₅GP reduced serum levels of adrenocorticotropic hormone/corticosterone and mRNA level of hypothalamic corticotrophin-releasing hormone. In conclusion, (Ac)₅GP treatment improved the depressive-like behaviors in CUMS rats perhaps by suppressing neuroinflammation in PFC and inhibiting activations of NF-κB and NLRP3 and also attenuating HPA axis hyperactivity.

Gardenia jasminoides Enhances CDDP-Induced Apoptosis of Glioblastoma Cells via AKT/mTOR Pathway While Protecting Death of Astrocytes

Gliomas are the most observed primary brain tumor, of which glioblastoma multiform (GBM) shows the highest incidence. Radiotherapy with temozolomide is the standard therapeutic method, but because of side effects, search for alternative therapies is required. Gardenia jasminoides (GJ) is flavonoid abundant with beneficial effects on inflammation, metabolic diseases, and cancers. In this study, we investigated the synergistic combination of GJ and cisplatin (CDDP) in U87MG and U373MG GBM cells. GJ and CDDP both showed cytotoxicity in U87MG cells, however GJ did not affect viability of normal astrocytes while CDDP displayed high toxicity. Cytotoxic effect of GJ and CDDP was related in apoptosis when confirmed by Western blot assays on cleaved caspase-3, caspase-9, and PARP. Moreover, GJ and CDDP showed synergistic combination in cell death of GBM cells, which was further confirmed by Western blot assays of apoptosis factors and also flow cytometry of Annexin V. Analysis on autophagy factors showed that GJ/CDDP combination induced autophagy, and through inhibition of autophagy, we could confirm autophagy is crucial to cytotoxicity of GJ/CDDP in GBM cell lines. The autophagy-mediated apoptosis of GJ/CDDP was dependent on the AKT/mTOR pathway. Overall, our results suggest GJ/CDDP combination as an effective yet safe therapeutic approach to GBMs.

Penta-acetyl geniposide induces apoptosis of fibroblast-like synoviocytes from adjuvant-induced arthritis rats in vitro, associated with inhibition of NF-κB activation

BACKGROUND

Approaches promoting fibroblast-like synoviocytes (FLS) apoptosis are considered as a meaningful strategy for rheumatoid arthritis (RA) treatment. We have previously reported the anti-arthritic effect of penta-acetyl geniposide ((Ac)5GP, an active derivative of geniposide) on adjuvant-induced arthritis (AIA) rats in vivo. The present study aimed to investigate the pro-apoptotic effect of (Ac)5GP on AIA FLS in vitro and the underlying molecular mechanisms.

METHODS

Rat AIA was induced by complete Freund's adjuvant, and FLS were primary-cultured from synovial tissues. AIA FLS were treated with (Ac)5GP (50, 100 and 200 μM) for 48 h and cell proliferation and apoptosis were respectively examined. The involvement of apoptosis-related proteins (Bax, Bcl-2 and caspase 3) and nuclear factor kappa B (NF-κB) signaling pathway was checked.

RESULTS

(Ac)5GP inhibited the viability of AIA FLS and reduced the percentage of Ki67-positive cells in AIA FLS. Particularly, (Ac)5GP promoted AIA FLS apoptosis in vitro by inducing apoptotic nuclear morphology, facilitating DNA ladder formation and increasing percentages of both early and late apoptotic cells. (Ac)5GP treatment on AIA FLS decreased Bcl-2 protein level whereas increased the levels of Bax and caspase 3 proteins. Moreover, (Ac)5GP reduced the degradation and phosphorylation of IκBα, down-regulated NF-κB p65 protein level in nucleus and inhibited NF-κB p65 nuclear translocation.

CONCLUSIONS

(Ac)5GP had a potent pro-apoptotic effect on AIA FLS in vitro, which is associated with regulating apoptosis-related proteins and inhibiting NF-κB activation.

Thymoquinone suppresses the proliferation of renal cell carcinoma cells via reactive oxygen species-induced apoptosis and reduces cell stemness

Thymoquinone is a phytochemical compound isolated from Nigella sativa and has various biological effects, including anti-inflammation, antioxidation, and anticancer. Here, we further investigated the anticancer effects and associated molecular mechanism of 2-methyl-5-isopropyl-1,4-benzoquinone (thymoquinone) on human renal carcinoma cell lines 786-O and 786-O-SI3 and transitional carcinoma cell line BFTC-909. Results showed that thymoquinone significantly reduced cell viability, inhibited the colony formation of renal cancer cells, and induced cell apoptosis and mitochondrial membrane potential change in both cancer cells. In addition, thymoquinone also triggered the production of reactive oxygen species (ROS) and superoxide and the activation of apoptotic and autophagic cascade. ROS inhibition suppressed the caspase-3 activation and restored the decreased cell viability of 786-O-SI3 in response to thymoquinone. Autophagy inhibition did not restore the cell viability of 786-O-SI3 suppressed by thymoquinone. Moreover, thymoquinone suppressed the cell sphere formation and the expression of aldehyde dehydrogenase, Nanog, Nestin, CD44, and Oct-4 in 786-O-SI3 cells. The tumor-bearing model showed that thymoquinone in vivo inhibited the growth of implanted 786-O-SI3 cell. All these findings indicate that thymoquinone inhibits the proliferation of 786-O-SI3 and BFTC-909 cell possibly due to the induction of ROS/superoxide and the consequent apoptosis, suggesting that thymoquinone may be a potential anticancer supplement for genitourinary cancer.

Mechanism of Rapid Nuclear Factor-E2-Related Factor 2 (Nrf2) Activation via Membrane-Associated Estrogen Receptors: Roles of NADPH Oxidase 1, Neutral Sphingomyelinase 2 and Epidermal Growth Factor Receptor (EGFR)

Membrane-associated estrogen receptors (ER)-α36 and G protein-coupled estrogen receptor (GPER) play important roles in the estrogen’s rapid non-genomic actions including stimulation of cell proliferation. Estrogen via these receptors induces rapid activation of transcription factor nuclear factor-E2-related factor 2 (Nrf2), a master regulator of detoxification and antioxidant systems, playing a key role in the metabolic reprogramming to support cell proliferation. This review highlights the possible mechanism underlying rapid Nrf2 activation via membrane-associated estrogen receptors by estrogen and phytoestrogens. Stimulation of ER-α36-GPER signaling complex rapidly induces Src-mediated transactivation of epidermal growth factor receptor (EGFR) leading to a kinase-mediated signaling cascade. We propose a novel hypothesis that ER-α36-GPER signaling initially induces rapid and temporal activation of NADPH oxidase 1 to generate superoxide, which subsequently activates redox-sensitive neutral sphingomyelinase 2 generating the lipid signaling mediator ceramide. Generation of ceramide is required for Ras activation and ceramide-protein kinase C ζ-casein kinase 2 (CK2) signaling. Notably, CK2 enhances chaperone activity of the Cdc37-Hsp90 complex supporting activation of various signaling kinases including Src, Raf and Akt (protein kinase B). Activation of Nrf2 may be induced by cooperation of two signaling pathways, (i) Nrf2 stabilization by direct phosphorylation by CK2 and (ii) EGFR-Ras-PI 3 kinase (PI3K)-Akt axis which inhibits glycogen synthase kinase 3β leading to enhanced nuclear transport and stability of Nrf2.

Plant-Derived Anticancer Agents: Lessons from the Pharmacology of Geniposide and Its Aglycone, Genipin

For centuries, plants have been exploited by mankind as sources of numerous cancer chemotherapeutic agents. Good examples of anticancer compounds of clinical significance today include the taxanes (e.g., taxol), vincristine, vinblastine, and the podophyllotoxin analogues that all trace their origin to higher plants. While all these drugs, along with the various other available therapeutic options, brought some relief in cancer management, a real breakthrough or cure has not yet been achieved. This critical review is a reflection on the lessons learnt from decades of research on the iridoid glycoside geniposide and its aglycone, genipin, which are currently used as gold standard reference compounds in cancer studies. Their effects on tumour development (carcinogenesis), cancer cell survival, and death, with particular emphasis on their mechanisms of actions, are discussed. Particular attention is also given to mechanisms related to the dual pro-oxidant and antioxidant effects of these compounds, the mitochondrial mechanism of cancer cell killing through reactive oxygen species (ROS), including that generated through the uncoupling protein-2 (UCP-2), the inflammatory mechanism, and cell cycle regulation. The implications of various studies for the evaluation of glycosidic and aglycone forms of natural products in vitro and in vivo through pharmacokinetic scrutiny are also addressed.

Neutral sphingomyelinases control extracellular vesicles budding from the plasma membrane

Extracellular vesicles (EVs) are membrane particles secreted from cells into all body fluids. Several EV populations exist differing in size and cellular origin. Using differential centrifugation EVs pelleting at 14,000 g ("microvesicles" (MV)) and 100,000 g ("exosomes") are distinguishable by protein markers. Neutral sphingomyelinase (nSMase) inhibition has been shown to inhibit exosome release from cells and has since been used to study their functional implications. How nSMases (also known as SMPD2 and SMPD3) affect the basal secretion of MVs is unclear. Here we investigated how SMPD2/3 impact both EV populations. SMPD2/3 inhibition by GW4869 or RNAi decreases secretion of exosomes, but also increases secretion of MVs from the plasma membrane. Both populations differ significantly in metabolite composition and Wnt proteins are specifically loaded onto MVs under these conditions. Taken together, our data reveal a novel regulatory function of SMPD2/3 in vesicle budding from the plasma membrane and clearly suggest that - despite the different vesicle biogenesis - the routes of vesicular export are adaptable.

Roles and regulation of neutral sphingomyelinase-2 in cellular and pathological processes

Our understanding of the functions of ceramide signaling has advanced tremendously over the past decade. In this review, we focus on the roles and regulation of neutral sphingomyelinase 2 (nSMase2), an enzyme that generates the bioactive lipid ceramide through the hydrolysis of the membrane lipid sphingomyelin. A large body of work has now implicated nSMase2 in a diverse set of cellular functions, physiological processes, and disease pathologies. We discuss different aspects of this enzyme's regulation from transcriptional, post-translational, and biochemical. Furthermore, we highlight nSMase2 involvement in cellular processes including inflammatory signaling, exosome generation, cell growth, and apoptosis, which in turn play important roles in pathologies such as cancer metastasis, Alzheimer's disease, and other organ systems disorders. Lastly, we examine avenues where targeted nSMase2-inhibition may be clinically beneficial in disease scenarios.

Protein Kinase C (PKC) Isozymes and Cancer

Protein kinase C (PKC) is a family of phospholipid-dependent serine/threonine kinases, which can be further classified into three PKC isozymes subfamilies: conventional or classic, novel or nonclassic, and atypical. PKC isozymes are known to be involved in cell proliferation, survival, invasion, migration, apoptosis, angiogenesis, and drug resistance. Because of their key roles in cell signaling, PKC isozymes also have the potential to be promising therapeutic targets for several diseases, such as cardiovascular diseases, immune and inflammatory diseases, neurological diseases, metabolic disorders, and multiple types of cancer. This review primarily focuses on the activation, mechanism, and function of PKC isozymes during cancer development and progression.

Drug targeting of sphingolipid metabolism: sphingomyelinases and ceramidases

Sphingolipids represent a class of diverse bioactive lipid molecules that are increasingly appreciated as key modulators of diverse physiologic and pathophysiologic processes that include cell growth, cell death, autophagy, angiogenesis, and stress and inflammatory responses. Sphingomyelinases and ceramidases are key enzymes of sphingolipid metabolism that regulate the formation and degradation of ceramide, one of the most intensely studied classes of sphingolipids. Improved understanding of these enzymes that control not only the levels of ceramide but also the complex interconversion of sphingolipid metabolites has provided the foundation for the functional analysis of the roles of sphingolipids. Our current understanding of the roles of various sphingolipids in the regulation of different cellular processes has come from loss-of-function/gain-of-function studies utilizing genetic deletion/downregulation/overexpression of enzymes of sphingolipid metabolism (e.g. knockout animals, RNA interference) and from the use of pharmacologic inhibitors of these same enzymes. While genetic approaches to evaluate the functional roles of sphingolipid enzymes have been instrumental in advancing the field, the use of pharmacologic inhibitors has been equally important in identifying new roles for sphingolipids in important cellular processes.The latter also promises the development of novel therapeutic targets with implications for cancer therapy, inflammation, diabetes, and neurodegeneration. In this review, we focus on the status and use of pharmacologic compounds that inhibit sphingomyelinases and ceramidases, and we will review the history, current uses and future directions for various small molecule inhibitors, and will highlight studies in which inhibitors of sphingolipid metabolizing enzymes have been used to effectively treat models of human disease.

Inhibition of neutral sphingomyelinase-2 perturbs brain sphingolipid balance and spatial memory in mice

The sphingolipid ceramide is a bioactive signaling lipid that is thought to play important roles in modulating synaptic activity, in part by regulating the function of excitatory postsynaptic receptors. However, the molecular mechanisms by which ceramide exerts its effects on synaptic activity remain largely unknown. We recently demonstrated that a rapid generation of ceramide by neutral sphingomyelinase-2 (nSMase2; also known as "sphingomyelin phosphodiesterase-3") played a key role in modulating excitatory postsynaptic currents by controlling the insertion and clustering of NMDA receptors (Wheeler et al. [2009] J. Neurochem. 109:1237-1249). We now demonstrate that nSMase2 plays a role in memory. Inhibition of nSMase2 impaired spatial and episodic-like memory in mice. At the molecular level, inhibition of nSMase2 decreased ceramide, increased PSD-95, increased the number of AMPA receptors, and altered the subunit composition of NMDA receptors. Our study identifies nSMase2 as an important component for efficient memory formation and underscores the importance of ceramide in regulating synaptic events related to learning and memory.

Ocimum gratissimum Aqueous Extract Induces Apoptotic Signalling in Lung Adenocarcinoma Cell A549

Ocimum gratissimum (OG) is widely used as a traditional herb for its antibacterial activity in Taiwan. Recently, antitumor effect of OG on breast cancer cell is also reported; however, the effects of OG on human pulmonary adenocarcinoma cell A549 remain unclear. Therefore, we aimed to investigate whether aqueous OG extract (OGE) affects viability of A549 cells and the signals induced by OGE in A549 cells. Cell viability assays revealed that OGE significantly and dose-dependently decreased the viability of A549 cell but not that of BEAS-2B cell. Morphological examination and DAPI staining indicated that OGE induced cell shrinkage and DNA condensation for A549 cells. Further investigation showed that OGE enhanced activation of caspase-3, caspase-9 and caspase-8 and increased protein level of Apaf-1 and Bak, but diminished the level of Bcl-2. Additionally, OGE inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) yet enhanced the phosphorylation of c-Jun N-terminal kinase (JNK) and p38 MAP kinase (p38). In conclusion, our findings indicate that OGE suppressed the cell viability of A549 cells, which may result from the activation of apoptotic signaling and the inhibition of anti-apoptotic signaling, suggesting that OGE might be beneficial to lung carcinoma treatment.

Ocimum gratissimum Aqueous Extract Protects H9c2 Myocardiac Cells from H(2)O(2)-Induced Cell Apoptosis through Akt Signalling

Increased cell death of cardiomyocyte by oxidative stress is known to cause dysfunction of the heart. O. gratissimum is one of the more well-known medicinal plants among the Ocimum species and widely used in treatment of inflammatory diseases. In this study, we hypothesized that aqueous extract of O. gratissimum leaf (OGE) may protect myocardiac cell H9c2 from oxidative injury by hydrogen peroxide (H₂O₂). Our results revealed that OGE pretreatment dose-dependently protects H9c2 cells from cell death when exposed to H₂O₂. Additionally, DNA condensation induced by H₂O₂ was also reduced by OGE pretreatment, suggesting that Ocimum gratissimum extract may attenuate H₂O₂-induced chromosome damage. Further investigation showed that OGE pretreatment inhibited H₂O₂-induced activation of caspase-3 and caspase-9, as well as H₂O₂-induced upregulation of proapoptotic Apaf-1 and the release of cytosolic cytochrome c, but has little effect on the activation of caspase-8. Additionally, OGE pretreatment significantly upregulated Bcl-2 expression and Akt phosphorylation, and slightly affected the phosphorylation of mitogen-activated protein kinases including p38 MAPK and JNK. Taken together, our findings revealed that Ocimum gratissimum extract effectively inhibited the mitochondrial pathway and upregulated Bcl-2 expression, which may be important in protecting H9c2 cells from H₂O₂-induced cell death.

Regulation of neutral sphingomyelinase-2 (nSMase2) by tumor necrosis factor-alpha involves protein kinase C-delta in lung epithelial cells

Neutral sphingomyelinases (N-SMases) are major candidates for stress-induced ceramide production, but there is still limited knowledge of the regulatory mechanisms of the cloned N-SMase enzyme-nSMase2. We have reported that p38 mitogen-activated protein kinase (MAPK) was upstream of nSMase2 in tumor necrosis-alpha (TNF-alpha)-stimulated A549 cells ( J Biol Chem 282: 1384-1396, 2007 ). Here, we report a role for protein kinase C (PKC) in mediating TNF-induced translocation of nSMase2 from the Golgi to the plasma membrane (PM). Pharmacological inhibition of PKCs prevented TNF-stimulated nSMase2 translocation to the PM in A549 cells. Using phorbol 12-myristate 13-acetate (PMA) as a tool to dissect PKC responses, we found that PMA induced nSMase2 translocation to the PM in a time- and dose-dependent manner. Pharmacological inhibitors and specific siRNA implicated the novel PKCs, specifically PKC-delta, in both TNF and PMA-stimulated nSMase2 translocation. However, PMA did not increase in vitro N-SMase activity and PKC-delta did not regulate TNF-induced N-SMase activity. Furthermore, PKC-delta and nSMase2 did not coimmunoprecipitate, suggesting that other signaling proteins may be involved. PMA-stimulated nSMase2 translocation was independent of p38 MAPK, and neither PKC inhibitors nor small interfering RNA had significant effects on TNF-stimulated p38 MAPK activation, indicating that PKC-delta does not act through p38 MAPK in regulating nSMase2. Finally, down-regulation of PKC-delta inhibited induction of vascular cell and intercellular adhesion molecules, previously identified as downstream of nSMase2 in A549 cells. Taken together, these data implicate PKC-delta as a regulator of nSMase2 and, for the first time, identify nSMase2 as a point of cross-talk between the PKC and sphingolipid pathways.