Expression of Cytosolic Phospholipase A2α in Murine C12 Cells, a Variant of L929 Cells, Induces Arachidonic Acid Release in Response to Phorbol Myristate Acetate and Ca2+ Ionophores, but Not to Tumor Necrosis Factor-α

Anticancer potential of Nymphaea nouchali Brum flowers against Ehrlich ascites carcinoma cell lines

Background

Nymphaea nouchali Brum is exotic and medicinal plant in India.

Aim of the Study

The main of this study is to evaluate the anticancer properties of Nymphaea nouchali Brum flowers against Ehrlich ascites carcinoma (EAC)-induced Swiss albino mice.

Materials and Methods

The anticancer properties of Nymphaea nouchali Brum dry and fresh methanol extracts was investigated using EAC in Swiss albino mice. After inoculation of EAC cells into mice, treatment with NNDM flower extract (200 and 400 mg/kg) and standard drug 5-Fluorouracil (20 mg/kg) was continued for 9 days. The evaluation of the effect of drug response was made by the study of tumor growth response including increase in lifespan, the study of hematological parameters, biochemical estimations, and antioxidant assay of liver tissue compared to EAC control. The viability of cancer cell lines (such as HeLa, MCF-7, and MDA-MB 231 cells) was evaluated by 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay.

Results

Therefore, from the results of the present study, it can be concluded that NNDM exhibited significant antitumor activity against EAC in Swiss albino mice. The effect of NNDM on viability of cancer cell lines (such as HeLa, MCF-7, and MDA-MB 231 cells) was evaluated by MTT assay, apoptosis in HeLa cell lines was evaluated by DNA laddering assay, HeLa cells treated with NNDM exhibited a characteristic "ladder" pattern after separation of the fragments by agarose gel electrophoresis and subsequent visualization, by ethidium bromide staining. NNDM exhibited a significant effect on cell viability.

Conclusions

Based on results, it was concluded that NNDM exhibited cytotoxic effect on cancer cells and, from DNA laddering assay, it can be concluded that NNDM-induced apoptosis in EAC cells.

Possible Involvement of Intracellular Calcium-Independent Phospholipase A2 in the Release of Secretory Phospholipases from Mast Cells-Increased Expression in Ileal Mast Cells of Crohn's Disease

Increased activity of secretory phospholipases A₂ (sPLA₂) type-II was previously observed in ileum of Crohn’s disease (CD). Our aims were to explore the involvement of calcium-independent (i)PLA₂β in the release of sPLA₂s from the human mast cell (MC) line (HMC-1) and investigate expressions of cytosolic (c)PLA₂α, iPLA₂β, sPLA₂-IIA and sPLA₂-V in MCs of CD ileum. The release of sPLA₂ was investigated in HMC-1 by immunocytochemistry and ELISA. The expression intensities of PLA₂s in mucosal MCs, and the proportion of PLA₂-positive MCs, were investigated in normal ileum and in ileum from patients with CD by immunohistochemistry. The calcium ionophore-stimulated release of sPLA₂-IIA and sPLA₂-V from HMC-1 was reduced by the iPLA₂-inhibitor bromoenol lactone. All four PLA₂s were detectable in mucosal MCs, both in normal ileum and in CD, but the proportion of iPLA₂β-containing mucosal MCs and the expression intensity of sPLA₂-IIA was increased in CD. Results indicate that iPLA₂β is involved in the secretion of sPLA₂s from HMC-1, and suggest that iPLA₂β-mediated release of sPLA₂ from intestinal MCs may contribute to CD pathophysiology. Ex vivo studies on isolated mucosal mast cells are however needed to clarify the precise role of MC PLA₂s in the inflammatory processes of CD.

Inhibition of Ehrlich ascites carcinoma by Manilkara zapota L. stem bark in Swiss albino mice

OBJECTIVE

To evaluate the antitumor activity of Manilkara zapota (M. zapota) L. stem bark against Ehrlich ascites carcinoma (EAC) in Swiss albino mice.

METHODS

The in vivo antitumour activity of the ethyl acetate extract of stem bark of M. zapota L. (EASM) was evaluated at 50, 100 and 200 mg/kg bw against EAC using mean survival time. After administration of the extract of M. zapota, viable EAC cell count and body weight in the EAC tumour hosts were observed. The animal was also observed for improvement in the haematological parameters (e.g., heamoglobin content, red and white blood cells count and differential cell count) after EASM treatment.

RESULTS

Intraperitoneal administration of EASM reduced viable EAC cells, increased the survival time, and restored altered haematological parameters. Significant efficacy was observed for EASM at 100 mg/kg dose (P<0.05).

CONCLUSIONS

It can be concluded that the ethyl acetate extract of stem bark of M. zapota L. possesses significant antitumour activity.

Isolation of a new triterpene derivative and in vitro and in vivo anticancer activity of ethanolic extract from root bark of Zizyphus nummularia Aubrev

The various parts of Zizyphus nummularia has been used traditionally in several disease conditions. However, its anticancer activity and mechanism of action remain to be elucidated. Considering this, the objective of this study was to isolate, identify and screen for possible anticancer activity in vitro and in vivo of the ethanolic extract (EE) and isolated identified compound (IC) from Z. nummularia root bark. The in vitro activity against human breast cancer, leukaemia, ovarian cancer, colon adenocarcinoma and human kidney carcinoma cell lines was determined. The in vivo activity in female Swiss albino mice against Ehrlich ascites carcinoma (EAC) was determined. The isolated compound is a new triterpene derivative. EE/IC showed cytotoxicity against different cell lines. The administration of EE/IC decreased tumour parameters such as tumour volume, viable tumour cell count and increased body weight, haematological parameters and life span in comparison to the EAC control mice.

In vitro antitumor assessments of peptide nanocomplexes on Dalton's lymphoma ascites tumor model

This research work reports the in vitro antitumor personality of few novel peptide nanocomplexes synthesized via a phase-assisted, modified Brust-Schiffrin methodology. Here, a series of metallo(copper, cobalt, nickel and zinc) nanocomplexes engineered with a pre-prepared peptide [N,N'-(1,2-ethylene)-bis-hippuricamide] have been synthesized for damaging the Dalton's lymphoma ascites tumor model. All the peptide nanocomplexes are spectrally, thermally and morphologically examined. The peptide bound zinc and cobalt nanocomplexes deliver excellent antitumor behavior against both the animal and human cancer cell lines, which has been pre-documented by their efficient DNA damaging skills under physiological conditions. Additionally, all the nanocomplexes are evaluated for the inhibition of microbial augmentation against few fungal and bacterial strains. The above results demonstrate that, a consecutive development of these kinds of peptide nanocomplexes may exemplify their uniqueness in biomedical applications as useful molecular-level devices.

Inhibition of cytosolic Phospholipase A2 prevents prion peptide-induced neuronal damage and co-localisation with Beta III Tubulin

Background

Activation of phospholipase A₂ (PLA₂) and the subsequent metabolism of arachidonic acid (AA) to prostaglandins have been shown to play an important role in neuronal death in neurodegenerative disease. Here we report the effects of the prion peptide fragment HuPrP106-126 on the PLA₂ cascade in primary cortical neurons and translocation of cPLA₂ to neurites.

Results

Exposure of primary cortical neurons to HuPrP106-126 increased the levels of phosphorylated cPLA₂ and caused phosphorylated cPLA₂ to relocate from the cell body to the cellular neurite in a PrP-dependent manner, a previously unreported observation. HuPrP106-126 also induced significant AA release, an indicator of cPLA₂ activation; this preceded synapse damage and subsequent cellular death. The novel translocation of p-cPLA₂ postulated the potential for exposure to HuPrP106-126 to result in a re-arrangement of the cellular cytoskeleton. However p-cPLA₂ did not colocalise significantly with F-actin, intermediate filaments, or microtubule-associated proteins. Conversely, p-cPLA₂ did significantly colocalise with the cytoskeletal protein beta III tubulin. Pre-treatment with the PLA₂ inhibitor, palmitoyl trifluoromethyl ketone (PACOCF₃) reduced cPLA₂ activation, AA release and damage to the neuronal synapse. Furthermore, PACOCF₃ reduced expression of p-cPLA₂ in neurites and inhibited colocalisation with beta III tubulin, resulting in protection against PrP-induced cell death.

Conclusions

Collectively, these findings suggest that cPLA₂ plays a vital role in the action of HuPrP106-126 and that the colocalisation of p-cPLA₂ with beta III tubulin could be central to the progress of neurodegeneration caused by prion peptides. Further work is needed to define exactly how PLA₂ inhibitors protect neurons from peptide-induced toxicity and how this relates to intracellular structural changes occurring in neurodegeneration.

Evaluation of antitumor activity of Mimusops elengi leaves on Ehrlich's ascites carcinoma-treated mice

CONTEXT

Mimusops elengi (M. elengi) Linn. (Sapotaceae) has been used as a folk medicine in wound healing, and the treatment of pain, and inflammation in many parts of India.

OBJECTIVE

The purpose of this investigation was to explore the antitumor activity of methanol extract of M. elengi (MEME) in Swiss albino mice against Ehrlich ascites carcinoma (EAC) cell line.

MATERIALS AND METHODS

Twenty-four hours after intraperitoneal (i.p.) inoculation of tumor (EAC) cells in mice (n = 12), MEME was administered at 200 and 300 mg/kg body weight daily for 9 consecutive days. On day 10, half of the mice were dissected and the rest were kept alive for assessment of increase in life span. The antitumor effect of MEME was assessed by evaluating tumor volume, viable and nonviable tumor cell count, tumor weight, hematological parameter, and biochemical estimations. In vivo antioxidant parameters were assayed by estimating liver tissue enzyme. In vitro cytotoxicity assay of MEME was measured by using trypan blue exclusion method.

RESULTS AND DISCUSSION

MEME showed significant (p < .001) decrease in tumor volume, packed cell volume, and viable cell count, and increased the life span of EAC bearing mice. Hematological, biochemical profile, and in vivo antioxidant parameters were significantly restored toward normal levels in MEME-treated mice as compared to EAC control. MEME also showed direct cytotoxicity on EAC cell line in a dose-dependent manner.

CONCLUSIONS

The present study demonstrates that M. elengi leaves exhibited antitumor activity in Swiss mice, which may be due to its cytotoxic effect and antioxidant properties.

Evaluation of antitumour activity of Calotropis gigantea L. root bark against Ehrlich ascites carcinoma in Swiss albino mice

OBJECTIVE

To investigate experimentally the possible antitumor effect of methanol extract (ME) of Calotropis gigantea L. (C. gigantean) root bark and its petroleum ether (PEF) and chloroform (CF) soluble fractions against Ehrlich ascites carcinoma (EAC) in Swiss albino mice.

METHODS

The effects of ME (10 and 20 mg/kg), PEF (40 and 80 mg/kg) and CF (20 and 40 mg/kg) on the growth of EAC and life span of EAC bearing mice were studied. Hematological profile and biochemical parameters (SALP, SGPT and SGOT) were also estimated.

RESULTS

Results of in vivo study showed a significant decrease in viable tumor cell count and a significant increase of life span in the ME and CF treated group compared to untreated one. The life span of ME and CF treated animals was significantly (P<0.05) increased by 43.90% (20 mg ME/kg) and 57.07% (40 mg CF/kg). ME and CF brought back the hematological parameter more or less normal level. ME and CF also restored the altered levels of serum alkaline phosphatase (SALP) and serum glutamate oxaloacetate transaminase (SGOT).

CONCLUSIONS

Methanol extract (ME) of C. gigantea root bark and its chloroform soluble fraction (CF) possesses significant antitumor activity.

Effect of malignant ascites on antioxidative potency of two tumoral cells-induced bone metastases: Walker 256/B and MatLyLu

This study was undertaken to estimate antioxidative status of two malignant-mammary gland carcinoma (Walker 256/B) and malignant-prostate carcinoma cells (MatLyLu) disseminated in ascitic fluids. Malignant carcinoma cells (10(7) cells) were twice serially intraperitoneal injected in male Wistar rats to develop ascites. After 7 days, ascitic fluids were collected, and cells in suspension were usable for biological assays. Cellular lipid peroxidation was assessed by measuring thiobarbituric acid reactive substances (TBARS) levels. Some antioxidant parameters: superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) were also assessed. Comparisons with control baseline (cells maintained in normal culture medium) were analyzed. TBARS levels were found to be significantly decreased in both ascitic cancer cells compared to the baseline except for in the ascite I of MatLyLu cells. On the other hand, SOD and CAT activities were found to be statistically increased in the two malignant ascitic passages. GSH-Px levels were elevated in the first and in the second ascitic passages (p<0.05 and p<0.01, respectively). Our results suggest that malignant ascites are associated not only with reduced levels of TBARS but also with increased antioxidant parameters, indicating the increasing antioxidant potency of two cancer cells during malignancies process.

Cytosolic PLA2(alpha) activation in Purkinje neurons and its role in AMPA-receptor trafficking

Cytosolic phospholipase A(2)alpha (cPLA(2)alpha) selectively releases arachidonic acid from membrane phospholipids and has been proposed to be involved in the induction of long-term depression (LTD), a form of synaptic plasticity in the cerebellum. This enzyme requires two events for its full activation: Ca(2+)-dependent translocation from the cytosol to organelle membranes in order to access phospholipids as substrates, and phosphorylation by several kinases. However, the subcellular distribution and activation of cPLA(2)alpha in Purkinje cells and the role of arachidonic acid in cerebellar LTD have not been fully elucidated. In cultured Purkinje cells, stimulation of AMPA receptors, but not metabotropic glutamate receptors, triggered translocation of cPLA(2)alpha to the somatic and dendritic Golgi compartments. This translocation required Ca(2+) influx through P-type Ca(2+) channels. AMPA plus PMA, a chemical method for inducing LTD, released arachidonic acid via phosphorylation of cPLA(2)alpha. AMPA plus PMA induced a decrease in surface GluR2 for more than 2 hours. Interestingly, this reduction was occluded by a cPLA(2)alpha-specific inhibitor. Furthermore, PMA plus arachidonic acid caused the prolonged internalization of GluR2 without activating AMPA receptors. These results suggest that cPLA(2)alpha regulates the persistent decrease in the expression of AMPA receptors, underscoring the role of cPLA(2)alpha in cerebellar LTD.

Release of arachidonic acid by 2-arachidonoyl glycerol and HU210 in PC12 cells; roles of Src, phospholipase C and cytosolic phospholipase A(2)alpha

The phospholipase A(2) (PLA(2))-prostanoid cascade is involved in cannabinoid receptor-mediated neuronal functions. We investigated the signaling mechanism for the release of arachidonic acid by cannabinoids, 2-arachidonoyl glycerol (2-AG) and HU210, in rat PC12 cells and in primary cultured cells from the mouse cerebellum. The effect of selective inhibitors for signaling pathways and/or enzymes (alpha type cytosolic PLA(2) (cPLA(2)alpha), G protein, Src kinases, phospholipase C, protein kinase C) was assessed. Methods included translocation of the chimeric protein GFP-cPLA(2)alpha, the activities of Src family kinases, Ca(2+)-dependent fluorescence and cyclic AMP accumulation. Treatment with 2-AG and HU210 at greater concentrations than 3 muM caused the release of arachidonic acid, and the response was inhibited by AM251 (an antagonist of cannabinoid CB(1) receptor) and by pyrrophenone (a selective inhibitor of cPLA(2)alpha) in PC12 cells. The cannabinoid treatment caused the intracellular translocation of cPLA(2)alpha and an increase in the intracellular Ca(2+) level. Treatment with HU210 caused tyrosine phosphorylation of Src and Fyn, and increased their kinase activities. Pretreatment with inhibitors of tyrosine kinases or phospholipase C abolished the cannabinoids-induced release of arachidonic acid and Ca(2+) response, and protein kinase C inhibitor reduced the release of arachidonic acid. 2-AG caused the release of arachidonic acid from cultured cells of the mouse cerebellum via similar mechanisms. These data reveal that cannabinoids activated cPLA(2)alpha in a Src-phospholipase C-protein kinase C-dependent manner probably via cannabinoid CB(1) receptor and/or CB(1)-like receptor in neuronal cells.

Ser515 phosphorylation-independent regulation of cytosolic phospholipase A2alpha (cPLA2alpha) by calmodulin-dependent protein kinase: possible interaction with catalytic domain A of cPLA2alpha

Calmodulin (CaM)-dependent protein kinase (CaM kinase) is proposed to regulate the type alpha of cytosolic phospholipase A(2) (cPLA(2)alpha), which has a dominant role in the release of arachidonic acid (AA), via phosphorylation of Ser515 of the enzyme. However, the exact role of CaM kinase in the activation of cPLA(2)alpha has not been well established. We investigated the effects induced by transfection with mutant cPLA(2)alpha and inhibitors for CaM and CaM kinase on the Ca(2+)-stimulated release of AA and translocation of cPLA(2)alpha. The mutation of Ser515 to Ala (S515A) did not change cPLA(2)alpha activity, although S228A and S505A completely and partially decreased the activity, respectively. Stimulation with hydrogen peroxide (H(2)O(2), 1 mM) and A23187 (10 microM) markedly released AA in C12 cells expressing S515A and wild-type cPLA(2)alpha, but the responses in C12-S505A, C12-S727A, and C12-S505A/S515A/S727A (AAA) cells were reduced. In HEK293T cells expressing cPLA(2)alpha, A23187 caused the translocation of the wild-type, the every mutants, cPLA(2)alpha-C2 domain, and cPLA(2)alpha-Delta397-749 lacking proposed phosphorylation sites such as Ser505 and Ser515. Treatment with inhibitors of CaM (W-7) and CaM kinase (KN-93) at 10 microM significantly decreased the release of AA in C12-cPLA(2)alpha cells and C12-S515A cells. KN-93 inhibited the A23187-induced translocation of the wild-type, S515A, AAA and cPLA(2)alpha-Delta397-749, but not cPLA(2)alpha-C2 domain. Our findings show a possible effect of CaM kinase on cPLA(2)alpha in a catalytic domain A-dependent and Ser515-independent manner.

Release of arachidonic acid induced by tumor necrosis factor-alpha in the presence of caspase inhibition: evidence for a cytosolic phospholipase A2alpha-independent pathway

Stimulation of L929 cells with tumor necrosis factor-alpha (TNFalpha) caused cell death accompanied by a release of arachidonic acid (AA). Although the inhibition of caspases has been shown to cause necrosis in TNFalpha-treated L929 cells, its role in the TNFalpha-induced release of AA has not been elucidated. The release of AA is tightly regulated by phospholipase A(2) (PLA(2)). To find out the mechanisms underlying the TNFalpha-induced release of AA, we investigated the relationship between TNFalpha stimulation and PLA(2) regulation with and without zVAD, an inhibitor of caspases. In the present study, we found that treatment with TNFalpha and zVAD stimulated release of AA and cell death in C12 cells (a variant of L929 cells lacking alpha type of cytosolic PLA(2) (cPLA(2)alpha)). Stimulation with TNFalpha/zVAD also caused the release of AA from L929-cPLA(2)alpha-siRNA cells. Treatment with pyrrophenone (a selective inhibitor of cPLA(2)alpha) completely inhibited the TNFalpha-induced release of AA, but only partially inhibited the TNFalpha/zVAD-induced response in L929 cells. The TNFalpha/zVAD-induced release of AA from C12 and L929-cPLA(2)alpha-siRNA cells was pyrrophenone-insensitive, but inhibited by treatment with butylated hydroxyanisole (BHA, an antioxidant). Treatment with dithiothreitol, which inactivates secretory PLA(2) activity, decreased the amount of AA released by TNFalpha/zVAD. TNFalpha/zVAD appears to stimulate release of AA from C12 cells in a cPLA(2)alpha-independent, BHA-sensitive manner. The possible roles of secretory PLA(2) and reactive oxygen species from different pools in the release of AA and cell death were discussed.

Antitumor Activity of the Methanol Extract of Hypericum hookerianum Stem Against Ehrlich Ascites Carcinoma in Swiss Albino Mice

A large number of plants belonging to the Hypericum family are known to possess strong antitumor properties. The methanol extract of H. hookerianum Wight and Arnott stem (MEHH) exhibited potent in vitro cytotoxic activity against various cancerous cell lines. In the present study, the high performance liquid chromatography (HPLC) standardized MEHH was tested for in vivo antitumor properties against Ehrlich ascites carcinoma (EAC) tumor bearing mice at 100, 200, and 400 mg/kg body weight doses given orally once daily for 14 days. The results indicate that administration of the extract not only increased the survival of animals with ascites tumor, decreased the body weight induced by the tumor burden, and reduced packed cell volume and viable tissue cell count, but also altered many hematological parameters changed during tumor progression, indicating the potent antitumor nature of the extract. Among the three doses tested, the 200 mg/kg body weight dose was found to be the most potent.

Vanadate-induced activation of cytosolic phospholipase A2α in L929 cells: Roles of tyrosine kinase, protein kinase C, and extracellular signal-regulated kinase

Orthovanadate (Na3VO4), which acts as an inhibitor of protein tyrosine phosphatases, has a various pharmacological effects including the release of arachidonic acid (AA) from cells. We investigated roles of alpha-type cytosolic phospholipase A2 (cPLA2alpha), Src family kinases (Src) and protein kinase C (PKC) in the release of AA induced by Na3VO4 from a murine fibroblast cell line, L929. C12 cells, a variant of L929 that lacks expression of cPLA2alpha, were used along with a clone of C12 cells that are stably expressing cPLA2alpha (C12-cPLA2alpha cells). In the presence of a Ca2+ ionophore (10 microM A23187), 5 and 10mM Na3VO4 synergistically stimulated AA release from L929 and C12-cPLA2alpha cells, and to a much lesser extent from control C12 cells. The release of AA by Na3VO4/A23187 was inhibited by a selective cPLA2alpha inhibitor (3 microM pyrrophenone). The release of AA by Na3VO4/A23187 was significantly inhibited by a PKC inhibitor (10 microM GF109203X), in PKC-depleted cells, by a Src inhibitor (2 microM PP2) and by an inhibitor of extracellular signal-regulated kinase 1/2 (ERK1/2) kinase (10 microM U0126). The phosphorylation of ERK1/2 was stimulated by Na3VO4, and the response was significantly decreased by inhibitors of Src, PKC and ERK1/2 kinase. Our data show that Na3VO4 stimulates AA release largely via cPLA2alpha activation in Ca2+-dependent manner, and the cross-talk between Src and PKC and the ERK-dependent pathways are involved in Na3VO4-induced AA release from L929 cells.

Antitumor Activity and Antioxidant Status of the Methanol Extract of Careya arborea Bark Against Dalton’s Lymphoma Ascites-Induced Ascitic and Solid Tumor in Mice

Based on the ethnomedical use of Careya arborea Roxb bark in the treatment of tumors, the present study was carried out to evaluate the anticancer potentials against Dalton's lymphoma ascites (DLA)-induced ascitic and solid tumors. The methanol extract of its bark given orally to mice at the dose of 250 or 500 mg/kg body weight for 10 days caused significant reduction in percent increase in body weight, packed cell volume, and viable tumor cell count when compared to the mice of the DLA control group. Restoration of hematological and biochemical parameters towards normal was also observed. Histological observations of liver and kidney also indicated repair of tissue damage caused by tumor inoculation. The extract at the dose of 5 or 25 mg/kg body weight given i.p. daily for 14 days significantly reduced the solid tumor volume induced by DLA cells.

Hydrogen peroxide-induced arachidonic acid release in L929 cells; roles of Src, protein kinase C and cytosolic phospholipase A2α

Hydrogen peroxide (H(2)O(2)) stimulates the release of arachidonic acid from cells, but the signaling mechanism(s) involved remains to be elucidated. We investigated the roles of alpha-type cytosolic phospholipase A(2) (cPLA(2)alpha), Src family kinases (Src) and protein kinase C (PKC) in the release of arachidonic acid from L929 cells (a murine fibroblast cell line), C12 cells (a variant of L929 that lacks cPLA(2)alpha) and a stable clone of C12 cells expressing cPLA(2)alpha (C12-cPLA(2)alpha cells). In the presence of 10 muM A23187, 100 nM phorbol myristate acetate (PMA) and 1 mM H(2)O(2) synergistically stimulated arachidonic acid release from L929 cells and C12-cPLA(2)alpha cells, and to a much lesser extent from C12 cells. The reagents alone and co-treatment with PMA and H(2)O(2) without A23187 had marginal effects. No arachidonic acid was released by PMA/A23187 or H(2)O(2)/A23187 in CaCl(2)-free buffer and the release was inhibited by a selective cPLA(2)alpha inhibitor (3 microM pyrrophenone). Addition of 10 microM H(2)O(2), which did not stimulate arachidonic acid release with A23187, enhanced the response to PMA/A23187. The release induced by PMA/A23187 and by H(2)O(2)/A23187 was significantly inhibited by a PKC inhibitor (10 microM GF109203X) and in PKC-depleted cells, and by a Src inhibitor (2 microM PP2). The phosphorylation of extracellular signal-regulated kinase 1/2 induced by PMA/A23187 and H(2)O(2)/A23187 was significantly decreased by inhibitors of PKC and Src. These findings suggest that H(2)O(2) with Ca(2+) stimulates arachidonic acid release via cPLA(2)alpha in a Src- and PKC-dependent manner in L929 cells. The role of cross-talk between Src and PKC in arachidonic acid release is discussed.