Biomedical subjects

J Hakim

Publications and source records attributed to J Hakim.

At least 55 records · Page 3Linked to original sources

PubMed1994

Immunochemical identification and translocation of protein kinase C zeta in human neutrophils.

Western blots of human polymorphonuclear leukocyte (PMN) extracts were immunostained with antibodies specific for various protein kinase C (PKC) isoforms. Two bands corresponding to PKC type zeta with apparent molecular masses of 81 kDa and 76 kDa were identified in the cytosolic fraction of resting cells, in addition to PKC types alpha and beta. PKC zeta was apparently abundant, like PKC beta, whereas PKC delta, -epsilon, and -gamma were not detectable. Following short stimulation (5 min) of PMN with phorbol-12-myristate-13-acetate (1 microgram/ml), physical translocation of PKC zeta from the cytosol to the plasma membrane fraction occurred, although this isoform does not bind phorbol esters. These data show that, in addition to the two calcium-dependent isoenzymes alpha and beta, human PMN express a calcium-independent isoenzyme zeta which translocates in stimulated cells, suggesting a role in the regulation of antibacterial activities.

Biological Transport↗

PubMed1994

Staurosporine up-regulates the expression of phorbol dibutyrate binding sites in human platelets.

Tumor-promoting phorbol esters bind to and activate protein kinase C (PKC). Staurosporine, a potent PKC inhibitor, interferes with PKC catalytic activity without altering phorbol ester binding sites in cell-free systems. We found that, unlike cell-free systems, treatment of intact platelets with staurosporine enhances the expression of phorbol 12, 13-dibutyrate (PDBu) binding sites. Incubation of platelets at 37 degrees with staurosporine (25 nM to 1 microM and 2 nM tritiated PDBu ([3H]PDBu) increased the amount of [3H]PDBu specifically bound to intact platelets by approximately 10 to 200% of control values. This effect was rapid and plateaued after 10 min of cell treatment. Scatchard analysis of the data showed that staurosporine (500 nM) significantly increased the total binding capacity Bmax from 42.9 +/- 15.4 x 10(3) to 78 +/- 7.3 x 10(3) sites per platelet and reduced the apparent dissociation constant value Kd from 30.8 +/- 8.6 nM to 9.4 +/- 3.4 nM. Enhanced PDBu binding capacity and affinity were also observed with human mononuclear and polymorphonuclear leukocytes. Fractionation of staurosporine-treated platelets showed an increased binding capacity of the particulate fraction (102%) and decreased binding capacity of the soluble fraction (60%) compared to controls, with no change in the affinity of PDBu binding to these fractions. Chelation of internal calcium with BAPTA did not significantly attenuate the staurosporine-mediated rise in PBDu binding but prevented the platelet-activating factor-induced response, indicating that cytosolic calcium does not play an important role in these staurosporine effects. These results show that, in addition to interfering with PKC protein-phosphorylating activity, staurosporine enhances PDBu binding affinity and capacity in intact platelets. This latter effect appears to be due to translocation of soluble PDBu binding sites, presumably PKC units.

Alkaloids↗

PubMed1994

Reactive oxygen species rapidly increase endothelial ICAM-1 ability to bind neutrophils without detectable upregulation.

We compared the effects of phorbol 12-myristate 13-acetate (PMA) and thrombin with those of nonlytic concentrations of reactive oxygen species (ROS) generated by hypoxanthine (HX)-xanthine oxidase (XO) on the adhesion properties of human umbilical cord vein endothelial cells (HUVEC) to resting polymorphonuclear neutrophils (PMN). PMN adherence to HX-XO-treated HUVEC was increased approximately twofold to 2.5-fold relative to untreated HUVEC, both immediately and after 2 hours. It was not additive to that induced by PMA or thrombin stimulation of HUVEC. ROS-induced adherence was not due to platelet-activating factor (PAF) or P-selectin expression, as it was neither antagonized by BN52021 (PAF receptor antagonist) nor inhibited by anti-P-selectin monoclonal antibody (MoAb), contrary to the increased adhesion of PMA- and thrombin-stimulated HUVEC. PMN preincubated with mannose-6-P or N-acetylneuraminic acid (sialic acid), but not mannose or galactose-6-P, showed reduced adherence to ROS-treated HUVEC, suggesting that carbohydrate molecules were expressed on the latter and served as the ligand for the PMN L-selectin. Intercellular adhesion molecule (ICAM-1), constitutively present on the surface of resting HUVEC, was involved in the PMN adherence to ROS-treated HUVEC, since this adherence was inhibited by anti-ICAM-1, anti-CD11a, anti-CD11b, and anti-CD18 MoAbs. A non-CD18, non-ICAM-1-dependent mechanism is also involved in this adherence, since effects of these MoAbs were not additive; moreover, combinations of anti-CD18 and anti-ICAM-1 MoAbs with mannose-6-P and sialic acid completely inhibited PMN adherence. The increased binding of PMN to HX-XO-exposed HUVEC observed here involved IC-AM-1, but was independent of its upregulation, and another non-ICAM-1-dependent mechanism, in which carbohydrates expressed on HUVEC recognize L-selectin on PMN.

Antibodies, Monoclonal↗

PubMed1994

W-7, a calmodulin antagonist, primes the stimulation of human neutrophil respiratory burst by formyl peptides and platelet-activating factor.

Low concentrations of the calmodulin antagonist W-7 (1-10 microM) enhanced the respiratory burst (RB) of human polymorphonuclear leukocytes (PMN) stimulated by N-formyl-methionyl-leucyl-phenylalanine, whereas high drug concentrations (above 20 microM) depressed it. The maximal increase obtained with 5-10 microM W-7 affected both initial rate (50%) and total superoxide anion production (150%). W-7 also primed both parameters of the RB mediated by platelet-activating factor, although higher drug concentrations were required (15-50 microM). By contrast, W-7 depressed the RB induced by the calcium ionophore A23187 and by a protein kinase C activator, phorbol myristate acetate, with an IC50 of approximately 20 and 8 microM, respectively. These data show the enhancing effect of W-7 on chemoattractant-mediated RB and suggest that RB priming may involve calmodulin-dependent regulation of chemoattractant-mediated early signalling events.

Calcimycin↗

PubMed1994

Cefdinir (CI-983), a new oral amino-2-thiazolyl cephalosporin, inhibits human neutrophil myeloperoxidase in the extracellular medium but not the phagolysosome.

Cefdinir, a new oral 2-amino-5-thiazolyl cephalosporin, inhibited the luminol-amplified chemiluminescence (LACL) response of human neutrophils stimulated by PMA but not opsonized zymosan, in a concentration-dependent but not time-dependent manner. The LACL response to opsonized zymosan in cytochalasin B-treated neutrophils was, however, inhibited by cefdinir. Various cephalosporins, regardless of the presence of a 2-amino-5-thiazolyl moiety, did not significantly alter the neutrophil LACL response triggered by PMA and zymosan. The LACL response induced by the calcium ionophore A23187 and FMLP was also impaired by cefdinir, and this impairment was increased in cytochalasin B-treated neutrophils. Superoxide anion generation by neutrophils, measured in terms of lucigenin-amplified chemiluminescence and cytochrome c reduction, was not altered. Spontaneous and FMLP-induced neutrophil degranulation, assessed by lysozyme and beta-glucuronidase release, were not modified by cefdinir. Furthermore, cefdinir inhibited LACL generation in cell-free systems consisting of H2O2, NaI, and either horseradish peroxidase or a myeloperoxidase-containing neutrophil extract. Orthodianisidine oxidation in these two acellular systems was inhibited by cefdinir. Cefdinir did not alter neutrophil bacterial killing at concentrations that inhibited myeloperoxidase-containing neutrophil extract-dependent reactions induced by soluble stimuli. Taken together, these data strongly suggest that cefdinir directly inhibits the activity of myeloperoxidase-containing neutrophil extract released into the extracellular medium during neutrophil stimulation by soluble mediators, but has no effect on that released into the phagolysosome during phagocytosis. This unusual property of a member of the beta-lactam family could be of interest in modulating the exaggerated inflammatory process often associated with infectious diseases.

Blood Bactericidal Activity↗

PubMed1994

p53 gene mutations as markers of tumor spread in synchronous oral cancers.

OBJECTIVE: To demonstrate how genetic mutations may be used as specific markers for the study and management of head and neck squamous cell carcinomas. DESIGN: Mutations in the p53 gene were identified by DNA sequencing in synchronous primary head and neck squamous cell carcinomas from one patient. The polymerase chain reaction and mutant-specific oligomer probes were used to detect rare tumor cells in surgical margins, lymph nodes, and swabs of the oral cavity. PATIENTS: Selected from a consecutive series of individuals with head and neck squamous cell carcinomas at a tertiary referral center. RESULTS: Two synchronous primary invasive cancers displayed different missense mutations in the p53 gene. The mutated sequence from one primary tumor was detected in metastases from both sides of the neck. Infiltrating cells from this biologically aggressive tumor were also detected by a polymerase chain reaction-based assay in a histologically normal surgical margin, accurately predicting tumor recurrence. CONCLUSIONS: p53 gene mutations were useful as molecular markers to distinguish between tumors in this case. The potential utility of detection of tumor cells in surgical margins and saliva by molecular techniques merits further investigation.

Biomarkers, Tumor↗

PubMed1994

Comparative sugar degradation by (OH). produced by the iron-driven Fenton reaction and gamma radiolysis.

We compared the attack of deoxyribose and mannitol by (OH). produced by gamma radiolysis or the iron-driven Fenton reaction. Deoxyribose (DR) oxidation by gamma radiolysis gave rise to thiobarbituric reactive substances (TBARS) with a yield of 17 mol (OH). per mole of TBARS. (OH). scavengers (benzoate, formate, and pentoxifylline) protected DR from oxidation. Mannitol was similarly oxidized by (OH). produced by gamma radiolysis, with a yield of 14 mol (OH). per mole of TBARS produced. A mixture containing both DR and mannitol gave rise to TBARS production with a yield of 9 mol (OH). per mole of TBARS superior to that of each product separately, suggesting the formation of secondary radicals responsible for the degradation of DR or mannitol. When (OH). was produced by the iron-driven Fenton reaction, DR gave rise to TBARS whereas mannitol did not. Furthermore, mannitol protected DR against degradation, apparently in the same way as desferrioxamine and diethylenetriaminepentaacetic acid, suggesting that it acts as an iron chelator. It can thus be assumed that, according to the site of (OH). production, sugar molecules are degraded as a function of their rate constant with (OH). or their iron chelating capacity.

Benzoates↗

PubMed1994

Resolution of major protein kinase substrates in neutrophil cytosol in response to DAG/PS and arachidonic acid stimulation and the selective action of various protein kinase inhibitors.

Stimulation of human neutrophils induces phosphorylation of several cellular proteins. Human neutrophils possess calcium-dependent protein kinase C (PKC) alpha and beta isoforms and calcium-independent n isoforms. Little is known, however, of the physiological substrates of each isoform. In this study, we characterized the substrates of calcium-dependent and -independent PKC isoforms and the substrate of PKC activated by arachidonic acid. Furthermore, we found that the PKC inhibitor H-7 failed to inhibit phosphorylation of endogenous substrates of calcium-independent PKC activity. These results may help to understand the role of PKC in neutrophil activation and shed light on the different responses elicited by H-7 in intact cells.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1994

Morbidity after crush injuries to the foot.

By retrospective review of hospital records and by follow-up clinical examinations, we evaluated 58 patients with crush injuries to the foot treated at our institution between 1986 and 1990. All patients had received initial treatment according to a standardized protocol determined by the type and magnitude of the injury. Patients were examined at a mean interval of 3.3 years (range 2-4) after injury, and the functional outcome was determined according to a foot trauma rating scale. Based on this scoring system, 46% of the patients had good functional outcome, 29% had fair results, and 25% had poor results. There was a significant correlation between a good functional outcome and careful adherence to the treatment protocol; however, some patients fared poorly regardless of treatment. Poor results occurred if treatment was not immediately initiated, if soft-tissue coverage was delayed (in those who experienced severe, mangling-type injuries necessitating partial foot amputation), if patients subsequently had neuritis or reflex sympathetic dystrophy, or if patients were involved in ongoing workers' compensation and litigation. We conclude that because crush injuries of the foot may be associated with prolonged morbidity, initial management should be directed toward recognition and treatment of compartment syndromes, early soft-tissue coverage, and rigid skeletal stabilization to enhance soft-tissue healing.

Activities of Daily Living↗

PubMed1994

Differential priming effects of proinflammatory cytokines on human neutrophil oxidative burst in response to bacterial N-formyl peptides.

Cytokines such as tumor necrosis factor alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 8 (IL-8), IL-6, IL-1 alpha, and IL-1 beta produced during the immune and inflammatory responses to bacterial stimuli have been reported to interact with polymorphonuclear neutrophil (PMN) activities. However, contradictory findings on their direct and priming effects on the PMN oxidative burst, which is essential for bacterial killing, have been reported. We have used a flow cytometry method to study the effects of these cytokines on the oxidative burst of PMN in whole blood to avoid PMN activation related to isolation procedures. None of the cytokines tested directly activated the PMN oxidative burst, but they did have differential priming effects on the oxidative burst in response to bacterial N-formyl peptides. TNF, GM-CSF, and IL-8 strongly primed a subpopulation of PMN to produce H2O2 in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP), while IL-1 alpha, IL-1 beta, and IL-6 failed to do so. Furthermore, the addition of TNF, GM-CSF, or IL-8 to whole blood increased the capacity of a subpopulation of PMN to bind N-formyl peptides, a phenomenon that could account, at least in part, for the strong H2O2 production in response to FMLP after priming by the cytokines. The size of the primed hyperresponsive subpopulation was greater after priming with TNF or GM-CSF than after priming with IL-8. However, GM-CSF, TNF, and IL-8 at suboptimal concentrations cooperated in the induction of a subpopulation hyperresponsive to FMLP. These results show that, of the various proinflammatory cytokines tested, TNF, GM-CSF, and IL-8 strongly prime the PMN oxidative burst in response to bacterial peptides in whole blood and suggest that these cytokines may play a critical role in bacterial killing in vivo.

Cytokines↗

PubMed1993

Endotoxin-induced tissue factor in human monocytes is dependent upon protein kinase C activation.

Tissue factor (TF) is a transmembrane receptor which, in association with factors VII and VIIa, activates factor IX and X, thereby activating the coagulation protease cascades. In response to bacterial lipopolysaccharide (LPS) monocytes transcribe, synthesize and express TF on their surface. We investigated whether LPS-induced TF in human monocytes is mediated by protein kinase C (PKC) activation. The PKC agonists phorbol 12-myristate 13-acetate (PMA) and phorbol 12, 13 dibutyrate (PdBu) were both potent inducers of TF in human monocytes, whereas 4 alpha-12, 13 didecanoate (4 alpha-Pdd) had no such effect. Both LPS- and PMA-induced TF activity were inhibited, in a concentration dependent manner, by three different PKC inhibitors: H7, staurosporine and calphostin C. TF antigen determination confirmed that LPS-induced cell-surface TF protein levels decreased in parallel to TF functional activity under staurosporine treatment. Moreover, Northern blot analysis of total RNA from LPS- or PMA-stimulated monocytes showed a concentration-dependent decrease in TF mRNA levels in response to H7 and staurosporine. The decay rate of LPS-induced TF mRNA evaluated after the arrest of transcription by actinomycin D was not affected by the addition of staurosporine, suggesting that its inhibitory effect occurred at a transcriptional level. We conclude that LPS-induced production of TF and its mRNA by human monocytes are dependent on PKC activation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1993

Oxidative damage to lysozyme by the hydroxyl radical: comparative effects of scavengers.

The hydroxyl radical (OH.) is a highly-damaging reactive oxygen species, given its high reactivity and the consequent generation of secondary free radicals. This study was aimed at determining the qualitative and quantitative aspects of OH. scavenging by pentoxifylline (Ptx, a methylxanthine), uric acid and thymine on the OH.-induced alterations of a protein, lysozyme. Lysozyme was inactivated by OH. with a yield of 6.5 mol OH./mol lysozyme; moreover, SDS-PAGE showed a loss of native lysozyme (14.4 kDa), the presence of dimer and trimer aggregates and characteristic fragmentation. Tryptophan fluorescence was lost before aggregation became detectable in terms of bityrosine formation. Increasing concentrations of OH. scavengers gave increasing protection of lysozyme activity. Although all three compounds scavenge OH. with high rate constants, their effects were different: uric acid and Ptx prevented aggregation and preserved enzyme activity, whereas thymine preserved activity but did not prevent aggregation. These differences appear to be related to the formation of reducing secondary radicals, underlining the importance of this mechanism in the effects of scavengers.

Free Radical Scavengers↗

PubMed1993

Stimulation of the human neutrophil respiratory burst by formyl peptides is primed by a protein kinase inhibitor, staurosporine.

Stimulation of polymorphonuclear neutrophils (PMN) by phorbol esters or formyl peptides (fMLP) generates large quantities of superoxide anion, the so-called respiratory burst (RB), a phenomenon associated with intense phosphorylation of a 47-kD protein (p47 phox). Staurosporine, a potent protein kinase C (PKC) antagonist, inhibits both responses when PMN are stimulated by phorbol myristate acetate (PMA), suggesting a positive role of PKC. In this study, we reassessed these PMN responses in fMLP-stimulated cells and found that staurosporine had opposite effects depending on the duration of PMN treatment with staurosporine. Short PMN incubation (0.5 to 3 minutes) with 25 to 100 nmol/L staurosporine inhibited the fMLP-induced RB, whereas longer treatment (15 to 20 minutes) enhanced it by up to about 200% relative to controls. In contrast, the PMA-mediated RB was depressed by staurosporine in a time-dependent manner. A primed fMLP-induced RB was also observed after long (15 minutes) PMN treatment with 5 to 100 mumol/L H-7, whereas shorter treatment (5 minutes) resulted in a small decrease in RB. By contrast, the tyrosine kinase inhibitor genistein (2 to 80 mumol/L) depressed fMLP-induced RB whatever the duration of PMN treatment. Analysis of 32P-phosphorylated proteins in fMLP-stimulated cells showed that short PMN treatment (< 8 minutes) with staurosporine abolished the phosphorylation of the 47-kD protein, which was identified as p47 phox, whereas long treatment partially restored p47 phox phosphorylation up to approximately 50% of the control value. In PMA-stimulated PMN, phosphorylation was reduced in a time-dependent manner. Furthermore, the staurosporine-primed RB and the staurosporine-induced recovery of phosphorylation were inhibited by sphingosine but not by genistein. Thus, in addition to its known depressive effect, staurosporine markedly potentiated fMLP-stimulated RB as a function of the duration of PMN treatment. The restoration of p47 phox phosphorylation suggests that staurosporine may alter the interactions between different protein kinases, producing marked time-dependent changes in signalling pathways. These data emphasize the care that should be taken in interpreting data obtained using this kinase inhibitor that may, however, be helpful analyzing in signalling pathways.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1993

The incidence of p53 mutations increases with progression of head and neck cancer.

To establish a genetic model of the progression of head and neck squamous carcinoma we have defined the incidence and timing of p53 mutations in this type of cancer. We sequenced the conserved regions of the p53 gene in 102 head and neck squamous carcinoma lesions. These included 65 primary invasive carcinomas and 37 noninvasive archival specimens consisting of 13 severe dysplasias and 24 carcinoma in situ lesions. The incidence of p53 mutations in noninvasive lesions was 19% (7/37) and increased to 43% (28/65) in invasive carcinomas. These data suggest that p53 mutations can precede invasion in primary head and neck cancer. Furthermore, the spectrum of codon hotspots is similar to that seen in squamous carcinoma of the lung and 64% of mutations are at G nucleotides, implicating carcinogens from tobacco smoke in the etiology of head and neck squamous carcinoma.

Adult↗

PubMed1993

Priming of polymorphonuclear neutrophils by tumor necrosis factor alpha in whole blood: identification of two polymorphonuclear neutrophil subpopulations in response to formyl-peptides.

We have used a cytofluorometric method to study the effect of tumor necrosis factor alpha (TNF) priming on the oxidative burst, FMLP-receptor expression and actin polymerization of whole blood polymorphonuclear neutrophils (PMN). This technique permits the study of single cells and, thus, allowed us to examine the responsiveness of PMN to TNF in whole blood. We found that TNF in whole blood strongly primed a subpopulation of PMN to produce H2O2 in response to FMLP stimulation, whereas TNF and FMLP alone did not have a significant effect. Furthermore, adding TNF to whole blood increased the capacity of a subpopulation of PMN to bind N-formyl peptides at 4 degrees C, a phenomenon that could account, at least in part, for the strong H2O2 production in response to FMLP after TNF priming. Dual-color cytometric analysis showed that TNF primed actin polymerization on the same subpopulation in response to FMLP. Because the PMN subpopulation, which strongly bound N-formyl peptides at 4 degrees C, was no longer detectable after 1 minute of incubation at 37 degrees C, our data suggest that TNF treatment of PMN in whole blood primes a subpopulation that actively cycles FMLP receptors. These results suggest that PMN in the circulation may respond weakly to bacterial peptides and that TNF may play a critical role in the induction of the oxidative burst in vivo.

Actins↗

PubMed1993

Pentoxifylline inhibits the expression of tissue factor mRNA in endotoxin-activated human monocytes.

Tissue factor (TF) is a transmembrane glycoprotein which, in association with factor VII(a), is the main activator of coagulation. In illnesses such as Gram-negative endotoxemia, circulating monocytes synthesize and express substantial TF activity, resulting in extensive disseminated intravascular coagulation. We investigated the way in which TF is suppressed by pentoxifylline (PTX), and found that PTX down-regulates immunologic TF expression and specific mRNA production in response to LPS. Since TF mRNA stability is not altered, this effect appears to take place at the transcriptional level.

Endotoxins↗

PubMed1993

A protein kinase inhibitor, staurosporine, enhances the expression of phorbol dibutyrate binding sites in human polymorphonuclear leucocytes.

Staurosporine, a potent protein kinase C (PKC) inhibitor, was studied for its effects on the binding of phorbol 12,13-dibutyrate (PDBu) to human polymorphonuclear leucocytes (PMNs). Treatment of PMNs with staurosporine concentrations in the range 50 nM-2 microM at 37 degrees C (but not at 4 degrees C) and with 1 nM [3H]PDBu at both temperatures enhanced specific PDBu binding to PMNs by approx. 10-600% relative to control values. The potentiation was rapid (detectable within 1 min) and reached a plateau after 10 min of cell treatment. Scatchard analysis of the binding showed that staurosporine increased the total number of PDBu-binding sites (Bmax) from (178 +/- 9) x 10(3) (control) to (324 +/- 15) x 10(3) sites per PMN and lowered the apparent dissociation constant (Kd) from 9.6 +/- 0.8 (control) to 3.3 +/- 0.3 nM. In Ca(2+)-depleted cells, staurosporine induced similar changes in Kd values, whereas the Bmax. increased by 60%. Treatment of PMNs with 500 nM staurosporine enhanced PDBu binding in the particulate fraction by 120 +/- 7% and decreased PDBu binding in the soluble fraction by 69 +/- 4%, whereas PKC histone-phosphorylating activity of both fractions was almost completely inhibited. Incubation of staurosporine-pretreated particulate fractions with soluble fractions enriched the particulate fraction in PDBu-binding sites at the expense of the soluble fraction, without altering the binding affinity of PDBu for either fraction. Stimulation of PMNs with chemotactic N-formyl peptides induced a transient increase in PDBu binding. This effect was potentiated by approx. 52% by staurosporine. These results show that, in addition to its interference with PKC protein-phosphorylating activity, staurosporine enhances both PDBu-binding capacity and affinity to PMNs, through a mechanism involving Ca(2+)-dependent and -independent processes. Alterations of PDBu binding to soluble and particulate fractions suggest that the enhanced binding capacity in intact PMNs may be due to translocation of PDBu receptors, presumably PKC units. This phenomenon may affect PKC-dependent cellular responses mediated by physiological stimulation.

Alkaloids↗

PubMed1993

Staurosporine stimulates phospholipase D activation in human polymorphonuclear leukocytes.

Treatment of 1-O-[3H]alkyl-2-acyl-phosphatidylcholine-prelabeled human polymorphonuclear leukocytes (PMNs) with staurosporine (50 nM to 1 microM) induced a time- and concentration-dependent generation of tritiated phosphatidic acid (PA), reaching approximately 225% of the control value at 15-20 min. In the presence of ethanol, staurosporine induced a production of phosphatidylethanol (PEt) reaching, 250% of control values, and partial inhibition of PA production, consistent with PLD activation. The amount of ether-linked acylglycerol (EAG) was weakly enhanced (29%) after 5 min of PMN treatment; longer treatment resulted in no significant EAG production, suggesting a possible late inhibition of PA hydrolase activity. Staurosporine concentrations that induced an elevation in PA completely depressed protein kinase C (PKC) activity in both soluble and particulate cell fractions, suggesting that PLD activation may occur independently from PKC activation. PLD may thus represent a potential cellular target for staurosporine action.

Alkaloids↗