High-titer production of staurosporine by heterologous expression and process optimization

Staurosporine is the most well-known member of the indolocarbazole alkaloid family; it can induce apoptosis of many types of cells as a strong protein kinase inhibitor, and is used as an important lead compound for the synthesis of the antitumor drugs. However, the low fermentation level of the native producer remains the bottleneck of staurosporine production. Herein, integration of multi-copy biosynthetic gene cluster (BGC) in well characterized heterologous host and optimization of the fermentation process were performed to enable high-level production of staurosporine. First, the 22.5 kb staurosporine BGC was captured by CRISPR/Cas9-mediated TAR (transformation-associated recombination) from the native producer (145 mg/L), and then introduced into three heterologous hosts Streptomyces avermitilis (ATCC 31267), Streptomyces lividans TK24 and Streptomyces albus J1074 to evaluate the staurosporine production capacity. The highest yield was achieved in S. albus J1074 (750 mg/L), which was used for further production improvement. Next, we integrated two additional staurosporine BGCs into the chromosome of strain S-STA via two different attB sites (vwb and TG1), leading to a double increase in the production of staurosporine. And finally, optimization of fermentation process by controlling the pH and glucose feeding could improve the yield of staurosporine to 4568 mg/L, which was approximately 30-fold higher than that of the native producer. This is the highest yield ever reported, paving the way for the industrial production of staurosporine. KEYPOINTS: • Streptomyces albus J1074 was the most suitable heterologous host to express the biosynthetic gene cluster of staurosporine. • Amplification of the biosynthetic gene cluster had obvious effect on improving the production of staurosporine. • The highest yield of staurosporine was achieved to 4568 mg/L by stepwise increase strategy.

Phosphorylation stabilized TET1 acts as an oncoprotein and therapeutic target in B cell acute lymphoblastic leukemia

Although the overall survival rate of B cell acute lymphoblastic leukemia (B-ALL) in childhood is more than 80%, it is merely 30% in refractory/relapsed and adult patients with B-ALL. This demonstrates a need for improved therapy targeting this subgroup of B-ALL. Here, we show that the ten-eleven translocation 1 (TET1) protein, a dioxygenase involved in DNA demethylation, is overexpressed and plays a crucial oncogenic role independent of its catalytic activity in B-ALL. Consistent with its oncogenic role in B-ALL, overexpression of TET1 alone in normal precursor B cells is sufficient to transform the cells and cause B-ALL in mice within 3 to 4 months. We found that TET1 protein is stabilized and overexpressed because of its phosphorylation mediated by protein kinase C epsilon (PRKCE) and ATM serine/threonine kinase (ATM), which are also overexpressed in B-ALL. Mechanistically, TET1 recruits STAT5B to the promoters of CD72 and JCHAIN and promotes their transcription, which in turn promotes B-ALL development. Destabilization of TET1 protein by treatment with PKC or ATM inhibitors (staurosporine or AZD0156; both tested in clinical trials), or by pharmacological targeting of STAT5B, greatly decreases B-ALL cell viability and inhibits B-ALL progression in vitro and in vivo. The combination of AZD0156 with staurosporine or vincristine exhibits a synergistic effect on inhibition of refractory/relapsed B-ALL cell survival and leukemia progression in PDX models. Collectively, our study reveals an oncogenic role of the phosphorylated TET1 protein in B-ALL independent of its catalytic activity and highlights the therapeutic potential of targeting TET1 signaling for the treatment of refractory/relapsed B-ALL.

Molecular Composition and Biological Activity of a Novel Acetonitrile-Water Extract of Lens Culinaris Medik in Murine Native Cells and Cell Lines Exposed to Different Chemotherapeutics Using Mass Spectrometry

We evaluated the effects of a new extract (70% acetonitrile, 2E0217022196DIPFARMTDA) of Lens culinaris Medik (Terre di Altamura SRL, Altamura BA) to prevent cytotoxic damage from cisplatin, staurosporine, irinotecan, doxorubicin, and the glucocorticoid dexamethasone. The acetonitrile-water extract (range 0.1-5 mg/mL) was obtained by extracting 10 g of lentil flour with 50 milliliters of the acetonitrile-water extraction mixture in a 70:30 ratio, first for 3 h and then overnight in a shaker at room temperature. The next day, the extract was filtered and passed through a Rotavapor to obtain only the aqueous component and eliminate that with acetonitrile, and then freeze-dried to finally have the powdered extract. In vitro experiments showed that the extract prevented the cytotoxic damage induced by cisplatin, irinotecan, and doxorubicin on HEK293 and SHSY5Y cell lines after 24-96 h. In murine osteoblasts after 24-72 h of incubation time, the extract was cytoprotective against all chemicals. The extract was effective against dexamethasone, leading to synergic cell proliferation in all cell types. In bone marrow cells, the extract is cytoprotective after 72 h against doxorubicin, staurosporine, and dexamethasone. Instead, on muscle fibers, the extract has a synergic effect with chemotherapeutics, increasing cytotoxicity induced by doxorubicin and staurosporine. LC-MS attested to the existence of several phenolic structures in the extract. The most abundant families of compounds were flavonoids (25.7%) and mellitic acid (18%). Thus, the development of this extract could be implemented in the area of research related to the chemoprevention of damage to renal, neuronal, bone marrow cells, and osteoblasts by chemotherapeutics; moreover, it could be used as a reinforcer of cytotoxic action of chemotherapeutics on muscle fibers.

A screening of inhibitors targeting the receptor kinase FERONIA reveals small molecules that enhance plant root immunity

Receptor-like kinases (RLKs) constitute the largest receptor family involved in the regulation of plant immunity and growth, but small-molecule inhibitors that target RLKs to improve agronomic traits remain unexplored. The RLK member FERONIA (FER) negatively regulates plant resistance to certain soil-borne diseases that are difficult to control and cause huge losses in crop yields and economy. Here, we identified 33 highly effective FER kinase inhibitors from 1494 small molecules by monitoring FER autophosphorylation in vitro. Four representative inhibitors (reversine, cenisertib, staurosporine and lavendustin A) inhibited the kinase activity of FER and its homologues in several crops by targeting the conserved ATP pocket in the kinase structure. FER contributes to the physiological impact of representative inhibitors in plants. The treatment of roots with reversine, staurosporine and lavendustin A enhanced innate immunity in plant roots and thus alleviated soil-borne diseases in tobacco, tomato and rice without growth penalties. Consistently, RNA sequencing assays showed that lavendustin A and reversine exert profound impacts on immunity-related gene expression. Our results will set a new milestone in the development of the plant RLK kinase regulation theory and provide a novel strategy for the prevention and control of plant soil-borne diseases without growth penalties.

Scalarane Sesterterpenoids Isolated from the Marine Sponge Hyrtios erectus and their Cytotoxicity

Eighteen scalarane sesterterpenoids (1–18), including eight new derivatives (1–8), were isolated from the sponge Hyrtios erectus (family Thorectidae), the extract of which showed cytotoxicity against the HeLa and MCF-7 cell lines. Of the new derivatives, six compounds (1–6) were found to contain a γ-hydroxybutenolide moiety capable of reversible stereoinversion at the hydroxylated carbon center. Under the influence of other adjacent functional groups, each derivative exhibited a different stereochemical behavior, which was fully deduced by ROESY experiments. All the isolated compounds were examined for their cytotoxicity by MTS assay using staurosporine as a positive control (IC50 0.18 and 0.13 μΜ against HeLa and MCF-7 cells, respectively), and they were found to show weak growth inhibitory activities against HeLa and MCF-7 cells, with a minimal IC50 value of 20.0 μΜ. The compounds containing a γ-hydroxybutenolide moiety (1–3, 10, 12) showed cytotoxicity, with IC50 values ranging from 24.3 to 29.9 μΜ, and the most potent derivative was heteronemin (16). Although the cytotoxicities of isolated compounds were insufficient to discuss the structure–activity relationship, this research could contribute to expanding the structural diversity of scalaranes and understanding the stereochemical behavior of γ-hydroxybutenolides.

Alzheimer's-associated PU.1 expression levels regulate microglial inflammatory response

More than forty loci contribute to genetic risk for Alzheimer's disease (AD). These risk alleles are enriched in myeloid cell enhancers suggesting that microglia, the brain-resident macrophages, contribute to AD risk. We have previously identified SPI1/PU.1, a master regulator of myeloid cell development in the brain and periphery, as a genetic risk factor for AD. Higher expression of SPI1 is associated with increased risk for AD, while lower expression is protective. To investigate the molecular and cellular phenotypes associated with higher and lower expression of PU.1 in microglia, we used stable overexpression and knock-down of PU.1 in BV2, an immortalized mouse microglial cell line. Transcriptome analysis suggests that reduced PU.1 expression suppresses expression of homeostatic genes similar to the disease-associated microglia response to amyloid plaques in mouse models of AD. Moreover, PU.1 knock-down resulted in activation of protein translation, antioxidant action and cholesterol/lipid metabolism pathways with a concomitant decrease of pro-inflammatory gene expression. PU.1 overexpression upregulated and knock-down downregulated phagocytic uptake in BV2 cells independent of the nature of the engulfed material. However, cells with reduced PU.1 expression retained their ability to internalize myelin similar to control albeit with a delay, which aligns with their anti-inflammatory profile. Here we identified several microglial responses that are modulated by PU.1 expression levels and propose that risk association of PU.1 to AD is driven by increased pro-inflammatory response due to increased viability of cells under cytotoxic conditions. In contrast, low expression of PU.1 leads to increased cell death under cytotoxic conditions accompanied by reduced pro-inflammatory signaling that decreased A1 reactive astrocytes signature supporting the protective effect of SPI1 genotype in AD. These findings inform future in vivo validation studies and design of small molecule screens for therapeutic discovery in AD.

Development of an HTS-compatible assay for the discovery of ASK1 signalosome inhibitors using alphascreen technology

Genetic target validation studies have demonstrated that the apoptosis signal-regulating kinase 1 (ASK1) represents an important target for the treatment of rheumatoid arthritis, cardiac diseases, and several neurodegenerative disorders. To identify small-molecule inhibitors of ASK1, we have developed a high-throughput screening-compatible, homogenous, biochemical assay using AlphaScreen technology. This novel assay design utilizes purified stress-activated ASK1 signalosome complex, and it monitors phosphorylation of its full-length native substrate, MKK6. The assay has been optimized in a 384-well format and validated by screening the Sigma LOPAC library. The results presented here demonstrate that the assay is sensitive and robust with a Z' factor value of 0.88±0.04 and a signal-to-background ratio of 11, indicating that this assay can be used to screen large chemical libraries to discover novel inhibitors of ASK1.

Wavelength-dependent backscattering measurements for quantitative real-time monitoring of apoptosis in living cells

Apoptosis--programmed cell death--is a cellular process exhibiting distinct biochemical and morphological changes. An understanding of the early morphological changes that a cell undergoes during apoptosis can provide the opportunity to monitor apoptosis in tissue, yielding diagnostic and prognostic information. There is avid interest regarding the involvement of apoptosis in cancer. The initial response of a tumor to successful cancer treatment is often massive apoptosis. Current apoptosis detection methods require cell culture disruption. Our aim is to develop a nondisruptive optical method to monitor apoptosis in living cells and tissues. This would allow for real-time evaluation of apoptotic progression of the same cell culture over time without alteration. Elastic scattering spectroscopy (ESS) is used to monitor changes in light-scattering properties of cells in vitro due to apoptotic morphology changes. We develop a simple instrument capable of wavelength-resolved ESS measurements from cell cultures in the backward direction. Using Mie theory, we also develop an algorithm that extracts the size distribution of scatterers in the sample. The instrument and algorithm are validated with microsphere suspensions. For cell studies, Chinese hamster ovary (CHO) cells are cultured to confluence on plates and are rendered apoptotic with staurosporine. Backscattering measurements are performed on pairs of treated and control samples at a sequence of times up to 6-h post-treatment. Initial results indicate that ESS is capable of discriminating between treated and control samples as early as 10- to 15-min post-treatment, much earlier than is sensed by standard assays for apoptosis. Extracted size distributions from treated and control samples show a decrease in Rayleigh and 150-nm scatterers, relative to control samples, with a corresponding increase in 200-nm particles. Work continues to correlate these size distributions with underlying morphology. To our knowledge, this is the first report of the use of backscattering spectral measurements to quantitatively monitor apoptosis in viable cell cultures in vitro.

Role of Protein Kinase-C in Thymocyte Apoptosis Induced by Irradiation

The role of protein kinase C in radiation-induced death of thymocytes was studied. For this purpose murine thymocytes were irradiated and incubated for 6 h at 37 degrees C and afterwards the fraction of fragmented DNA was measured. Results indicate that radiation-induced DNA fragmentation can be prevented by adding the protein kinase C inhibitor H-7 or staurosporine to the thymocytes during incubation time. Incubation of irradiated cells with HA-1004, an inhibitor of cAMP-dependent protein kinase, with a minor effect on protein kinase C did not affect the DNA fragmentation induced by irradiation. Incubation of cells with phorboldibutyrate gave a dose-dependent induction of DNA fragmentation. This effect can be inhibited by staurosporine. These results suggest that radiation-induced DNA fragmentation is an active cellular process in which protein kinase C plays an important role.

An impedimetric microelectrode-based array sensor for label-free detection of tau hyperphosphorylation in human cells

Tauopathies such as Alzheimer's disease (AD) belong to the group of neurodegenerative diseases that are characterised by hyperphosphorylation of the protein tau. Hyperphosphorylation of tau is one of the salient events leading to neuronal cytotoxicity and cognitive impairments. In this context, inhibition of tau hyperphosphorylation by specific tau kinase inhibitors can provide an excellent drug target for the treatment of AD and other tau-related neurodegenerative diseases. To improve the identification, optimisation and validation during the high-cost hit-to-lead cycle of AD drugs, we established a fast and sensitive label-free technique for testing the efficacy of tau kinase inhibitors in vitro. Here, we report for the first time that microelectrode-based impedance spectroscopy can be used to detect the pathological risk potential of hyperphosphorylated tau in the human neuroblastoma cell line SH-SY5Y. Our findings provide a novel real-time recording technique for testing the efficiency of tau kinase inhibitors or other lead structures directed to tau hyperphosphorylation on differentiated SH-SY5Y cells.

A point mutation in the putative ATP binding site of the pseudorabies virus US3 protein kinase prevents Bad phosphorylation and cell survival following apoptosis induction

The multifunctional US3 protein kinase is conserved among alphaherpesviruses. Like the herpes simplex virus US3 protein kinase, the pseudorabies virus (PRV) US3 protein confers resistance against apoptosis. In the current report, we introduced a point mutation in the putative ATP binding site of the PRV US3 protein kinase. We found that, in contrast to the wild type PRV US3, the point-mutated PRV US3 does not protect cells from apoptosis induced by PRV infection or staurosporine treatment. In addition, we found that the presence of wild type PRV US3, but not of the point-mutated PRV US3, results in phosphorylation of the pro-apoptotic Bad protein in PRV-infected ST and HEp-2 cells. In PRV-infected ST cells, but not in HEp-2 cells, an additional, US3- and phosphorylation-independent alteration of Bad could be observed. These results suggest that the kinase activity of the US3 protein of PRV is crucial to protect cells from apoptotic cell death during infection, at least partly by leading to phosphorylation of the pro-apoptotic Bad protein.

Microarrays for the functional analysis of the chemical-kinase interactome

A central challenge in chemical biology is profiling the activity of a large number of chemical structures against hundreds of biological targets, such as kinases. Conventional 32P-incorporation or immunoassay of phosphorylated residues produces high-quality signals for monitoring kinase reactions but is difficult to use in high-throughput screening (HTS) because of cost and the need for well-plate washing. The authors report a method for densely archiving compounds in nanodroplets on peptide or protein substrate-coated microarrays for subsequent profiling by aerosol deposition of kinases. Each microarray contains over 6000 reaction centers (1.0 nL each) whose phosphorylation progress can be detected by immunofluorescence. For p60c-src, the microarray produced a signal-to-background ratio of 36.3 and Z' factor of 0.63 for HTS and accurate enzyme kinetic parameters (KmATP = 3.3 microM) and IC50 values for staurosporine (210 nM) and PP2 (326 nM) at 10 microM adenosine triphosphate (ATP). Similarly, B-Raf phosphorylation of MEK-coated microarrays was inhibited in the nanoliter reactions by GW5074 at the expected IC50 of 9 nM. Common kinase inhibitors were printed on microarrays, and their inhibitory activities were systematically profiled against B-Raf (V599E), KDR, Met, Flt-3 (D835Y), Lyn, EGFR, PDGFRbeta, and Tie2. All results indicate that this platform is well suited for kinetic analysis, HTS, large-scale IC50 determinations, and selectivity profiling.

Effect of staurosporine-induced apoptosis on endothelial nitric oxide synthase in transfected COS-7 cells and primary endothelial cells

Nitric oxide (NO) may block apoptosis by inhibiting caspases via S-nitrosylation of cysteines. Here, we investigated whether effector caspases might cleave and thereby inhibit endothelial nitric oxide synthase (eNOS). Exposure of eNOS-transfected COS-7 cells and bovine aortic endothelial cells to staurosporine resulted in significant loss of 135-kDa eNOS protein and activity, and appearance of a 60-kDa eNOS fragment; effects were inhibited by the general caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp[OMe]-fluoromethyl ketone (zVAD-fmk). In eNOS-transfected COS-7 cells, staurosporine-induced activation of caspase-3 and poly(ADP-ribose) polymerase (PARP) cleavage coincided with increased eNOS degradation and decreased activity. Loss of eNOS activity was greater than the degree of proteolysis. Incubation of immunoprecipitated eNOS with caspase-3, caspase-6 or caspase-7 resulted in eNOS cleavage. Staurosporine, a general protein kinase inhibitor, also reduced phosphorylation and decreased calmodulin binding, an effect that may explain the reduction in activity. eNOS, therefore, is both an inhibitor of apoptosis and a target of apoptosis-associated proteolysis.

Diosgenin dose-dependent apoptosis and differentiation induction in human erythroleukemia cell line and sedimentation field-flow fractionation monitoring

To limit or stop cancer spreading, one of the most prevalent strategies is to induce cancer cell death. Differentiation therapy and apoptosis induction are two ways to achieve this goal. Sedimentation field-flow fractionation (SdFFF) has been described as an effective tool for cell separation, respecting integrity and viability. Because SdFFF takes advantage of intrinsic properties of eluted cells (size, density, shape), we studied the capacity of SdFFF to monitor specific biophysical modifications that occurred during cellular apoptosis or differentiation induction. Then, we used, as an in vitro cellular model of apoptosis and differentiation, diosgenin dose-dependent induction in the polyvalent human erythroleukemia cell line. Two other chemicals were used: phorbol myristate acetate (differentiation inducer) and staurosporine (apoptosis inducer). Our results demonstrated a correlation between SdFFF elution profile changes and induction of effective biological processes. Thus, after acquisition of a reference profile, SdFFF could be used alone to follow chemically induced biological events, suggesting many different applications such as testing series of molecules, evaluation of new cellular/biological models used in different life science fields, or sorting purified populations with the aim of better understanding mechanisms of induced cellular events.

Externalization of phosphatidylserine during apoptosis does not specifically require either isoform of phosphatidylserine synthase

Phosphatidylserine (PtdSer) is made in mammalian cells by two PtdSer synthases, PSS1 and PSS2. In the plasma membrane PtdSer is normally localized on the inner leaflet but undergoes transbilayer movement during apoptosis and becomes exposed on the cell surface. We induced apoptosis with staurosporine in four Chinese hamster ovary (CHO) cell lines that are deficient in PSS1 and/or PSS2 to determine if PtdSer generated by either of these enzymes is required for externalization on the cell surface during apoptosis. The onset of apoptosis was confirmed by the appearance of morphological changes and DNA fragmentation while the plasma membrane remained largely intact. In all cell lines, regardless of their content of PSS1 and/or PSS2, apoptosis occurred to approximately the same extent, and within approximately the same time frame, as in parental CHO-K1 cells. The exposure of PtdSer on the cell surface was assessed by annexin V labeling and flow cytometry. Cells that were deficient in either PSS1 or PSS2, as well as cells that were deficient in both PSS1 and PSS2, externalized normal amounts of PtdSer. Our study demonstrates, that reduction of in vitro serine-exchange activity, even by 97%, does not restrict the externalization of PtdSer during apoptosis. Moreover, a normal level of expression of PSS1 and/or PSS2 is not required for generating the pool of PtdSer externalized during apoptosis.

Bovine DNase I: gene organization, mRNA expression, and changes in the topological distribution of the protein during apoptosis in lens epithelial cells

Genomic DNA sequencing and alignment with the known DNase I mRNA showed that the bovine gene consists of 9 exons and that only the last 8 encode the protein, since initial ATG was found at exon II. RT-PCR was used to identify DNase I mRNA in lens epithelium in vivo and in cultured epithelial cells. We found DNase I transcripts having the same nucleotide sequence as the pancreas form and others lacking almost all exon V. The lens protein presented a slightly higher relative molecular weight than the pancreatic enzyme. Lens DNase I was located in secretory pathway organelles and excluded from the nucleus. Nevertheless, in apoptotic lens epithelial cells in vitro, DNase I translocated to the nucleus and co-localized with TUNEL positive chromatin aggregates. These results indicate that cells in the lens epithelium constitutively express DNase I, and suggest a direct involvement of this nuclease in the final phases of chromatin degradation.

Effect of Bacillus anthracis lethal toxin on human peripheral blood mononuclear cells

Lethal toxin (LeTx) plays a central role in anthrax pathogenesis, however a cytotoxicity of LeTx has been difficult to demonstrate in vitro. No cytolytic effect has been reported for human cells, in contrast to murine cell lines, indicating that cell lysis can not be considered as a marker of LeTx activity. We have recently shown that murine macrophage-like RAW 264.7 cells treated with LeTx or infected with anthrax spores underwent changes typical of apoptotic death. Here we demonstrate that cells from human peripheral blood display a proapoptotic behavior similar to murine cells. TUNEL assay detected a nucleosomal degradation typical of apoptosis in peripheral blood mononuclear cells (PBMC) treated with LeTx. Membrane staining with apoptotic dyes was detected in macrophages derived from monocytes in presence of LeTx. The toxin inhibited production of proinflammatory cytokines in PBMC stimulated with a preparation of Bacillus anthracis cell wall. Infection of PBMC with anthrax spores led to the appearance of a large population of cells stained positively for apoptosis, with a reduced capacity to eliminate spores and vegetative bacteria. The aminopeptidase inhibitor, bestatin, capable of protecting cells from LeTx, restored a bactericidal activity of infected cells. These findings may be explained by LeTx expression within phagocytes and support an important role of LeTx as an early intracellular virulence factor contributing to bacterial dissemination and disease progression.

L-Carnitine: a potential treatment for blocking apoptosis and preventing skeletal muscle myopathy in heart failure

Skeletal muscle in congestive heart failure is responsible for increased fatigability and decreased exercise capacity. A specific myopathy with increased expression of fast-type myosins, myocyte atrophy, secondary to myocyte apoptosis triggered by high levels of circulating tumor necrosis factor-alpha (TNF-alpha) has been described. In an animal model of heart failure, the monocrotaline-treated rat, we have observed an increase of apoptotic skeletal muscle nuclei. Proapoptotic agents, caspase-3 and -9, were increased, as well as serum levels of TNF-alpha and its second messenger sphingosine. Treatment of rats with L-carnitine, known for its protective effect on muscle metabolism injuries, was found to inhibit caspases and to decrease the levels of TNF-alpha and sphingosine, as well as the number of apoptotic myonuclei. Staurosporine was used in in vitro experiments to induce apoptosis in skeletal muscle cells in culture. When L-carnitine was applied to skeletal muscle cells, before staurosporine treatment, we observed a reduction in apoptosis. These findings show that L-carnitine can prevent apoptosis of skeletal muscles cells and has a role in the treatment of congestive heart failure-associated myopathy.

PKC-independent inhibition of glutamate exocytosis by arachidonic acid in rat cerebrocortical synaptosomes

In rat cerebrocortical synaptosomes, the addition of 4 beta-phorbol dibutyrate (4 beta-PDBu) and arachidonic acid enhances and decreases, respectively, the glutamate release evoked by 4-aminopyridine. Pretreatment of synaptosomes with 12-O-tetradecanoylphorbol 13-acetate (TPA) or pre-incubation with staurosporine, prevent the stimulatory effect of 4 beta-PDBu, but are without effect on the inhibitory action of arachidonic acid. Moreover, methyl arachidonate, which is not effective as a PKC activator, also strongly inhibits glutamate exocytosis. These results suggest that PKC is not involved in the inhibition of glutamate release by arachidonic acid.

Staurosporine induces a neuronal phenotype in SH-SY5Y human neuroblastoma cells that resembles that induced by the phorbol ester 12-O-tetradecanoyl phorbol-13 acetate TPA)

Treatment of SH-SY5Y human neuroblastoma cells with the protein kinase inhibitor staurosporine, induced both morphological and functional differentiation in these cells. The effects of staurosporine were comparable to those induced by the protein kinase C (PKC) activator, 12-O-tetradecanoyl phorbol 13-acetate (TPA), with respect to induction of neuronal differentiation, i.e. neurite outgrowth, inhibition of DNA synthesis, induction and down-regulation of c-myc protein expression, induction of mRNA for both neuropeptide Y (NPY) and growth associated protein 43 (GAP-43) and stimulation of tyrosine hydroxylase expression. Staurosporine failed to translocate PKC to the membrane fraction or to stimulate phosphorylation of the endogenous PKC substrate M(r) 80,000 (p80). Instead, staurosporine inhibited TPA-induced phosphorylation of p80.

Caspase-3-mediated processing of poly(ADP-ribose) glycohydrolase during apoptosis

Poly(ADP-ribose) glycohydrolase (PARG) is responsible for the catabolism of poly(ADP-ribose) synthesized by poly(ADP-ribose) polymerase (PARP-1) and other PARP-1-like enzymes. In this work, we report that PARG is cleaved during etoposide-, staurosporine-, and Fas-induced apoptosis in human cells. This cleavage is concomitant with PARP-1 processing and generates two C-terminal fragments of 85 and 74 kDa. In vitro cleavage assays using apoptotic cell extracts showed that a protease of the caspase family is responsible for PARG processing. A complete inhibition of this cleavage was achieved at nanomolar concentrations of the caspase inhibitor acetyl-Asp-Glu-Val-Asp-aldehyde, suggesting the involvement of caspase-3-like proteases. Consistently, recombinant caspase-3 efficiently cleaved PARG in vitro, suggesting the involvement of this protease in PARG processing in vivo. Furthermore, caspase-3-deficient MCF-7 cells did not show any PARG cleavage in response to staurosporine treatment. The cleavage sites identified by site-directed mutagenesis are DEID(256) downward arrow V and the unconventional site MDVD(307) downward arrow N. Kinetic studies have shown similar maximal velocity (V(max)) and affinity (K(m)) for both full-length PARG and its apoptotic fragments, suggesting that caspase-3 may affect PARG function without altering its enzymatic activity. The early cleavage of both PARP-1 and PARG by caspases during apoptosis suggests an important function for poly(ADP-ribose) metabolism regulation during this cell death process.

Phosphatidyl serine exposure during apoptosis precedes release of cytochrome c and decrease in mitochondrial transmembrane potential

Time kinetics of phosphatidyl serine (PS) exposure were compared to other apoptotic parameters following different apoptotic stimuli. Our data indicate that anti-Fas treatment of L929sAhFas cells results in rapid exposure of PS, which precedes decrease in mitochondrial transmembrane potential (DeltaPsi(m)) and release of cytochrome c, indicating that PS exposure occurs independently of these mitochondrial events. Also during TNF-, etoposide- or staurosporine-mediated apoptosis in PC60 RI/RII cells, PS-positive cells were observed before they had a decreased DeltaPsi(m). However, during growth factor depletion-induced death of 32D cells, both phenomena seemed to occur at the same time.

Resistance of initiation factor 2 (eIF-2alpha) kinases to staurosporine: an approach for assaying the kinases in crude extracts

We studied the effect of staurosporine on two well characterised mammalian eIF-2alpha kinases, the heme-regulated translational inhibitor (HRI), and interferon-inducible double-stranded RNA-activated protein kinase (PKR). Both pure eIF-2 and a synthetic peptide used to measure the activity of purified or immunoprecipitated enzymes (sequence ILLSELSRRRIRAI) were phosphorylated with purified enzymes and crude preparations of tissues or cells in the presence of the inhibitor. In the presence of 0.25 microM staurosporine (a concentration which completely inhibits a wide range of Ser/Thr protein kinases), the phosphorylation of eIF-2alpha by HRI and PKR was not inhibited. The lack of response of eIF-2alpha kinases to staurosporine allowed us to measure PKR activity in salt washed postmicrosomal supernatants without previous purification of the enzyme. In the presence of poly(I):poly(C), the PKR activator, we detected both an increased phosphorylation of eIF-2alpha and an increment in the autophosphorylation of PKR. We also confirmed an induction of PKR in cultured neuronal cells after treatment with interferon. The results obtained following phosphorylation of the synthetic peptide with crude extracts are less conclusive. Although its phosphorylation is specific because it displaces eIF-2 phosphorylation, and the presence of staurosporine prevents its phosphorylation by other serine/threonine kinases, it is a rather poor substrate for PKR.

The 5-HT1A receptor agonist BAY x 3702 prevents staurosporine-induced apoptosis

The 5-HT1A receptor agonist (-)-(R)-2-[4-[[(3,4-dihydro-2H-1-benzopyran-2-yl)methyl]amino]butyl]-1,2 -benzisothiazol-3(2H)-one1,1-dioxide monohydrochloride (BAY x 3702) was recently shown to have pronounced neuroprotective effects in rat models of cerebral ischemia and traumatic brain injury. In the present study we investigated the neuroprotective effects of BAY x 3702 in primary cultures of hippocampal and cortical neurons. Cell death was induced by 25 nM of the apoptosis inducing agent staurosporine and analyzed 24 h later by release of lactate dehydrogenase, formation of apoptotic bodies and DNA fragmentation. A significant neuroprotection was seen after pretreatment of the affected neurons with 50 pM to 1 microM BAY x 3702. The effects of BAY x 3702 were completely blocked by the selective 5-HT1A receptor antagonist N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride) (WAY-100635). These results indicate that low concentrations of BAY x 3702 protect cortical as well as hippocampal neurons from apoptotic cell death via a 5-HT1A receptor mediated pathway.

Tyrosine phosphorylation of I kappa B-alpha activates NF-kappa B without proteolytic degradation of I kappa B-alpha

The transcription factor NF-kappa B regulates genes participating in immune and inflammatory responses. In T lymphocytes, NF-kappa B is sequestered in the cytosol by the inhibitor I kappa B-alpha and released after serine phosphorylation of I kappa B-alpha that regulates its ubiquitin-dependent degradation. We report an alternative mechanism of NF-kappa B activation. Stimulation of Jurkat T cells with the protein tyrosine phosphatase inhibitor and T cell activator pervanadate led to NF-kappa B activation through tyrosine phosphorylation but not degradation of I kappa B-alpha. Pervanadate-induced I kappa B-alpha phosphorylation and NF-kappa B activation required expression of the T cell tyrosine kinase p56ick. Reoxygenation of hypoxic cells appeared as a physiological effector of I kappa B-alpha tyrosine phosphorylation. Tyrosine phosphorylation of I kappa B-alpha represents a proteolysis-independent mechanism of NF-kappa B activation that directly couples NF-kappa B to cellular tyrosine kinase.

Inhibition of HIV-1 Tat-mediated transactivation by quinacrine and chloroquine

The replication of human immunodeficiency virus type 1 (HIV-1) requires cellular components to interact with regulatory elements located in the long terminal repeat (LTR) as well as viral proteins Tat and Rev. Several well known signaling transduction inhibitors were tested to determine their effects on the Tat-mediated transactivation using a transfection assay with the bacterial chloramphenicol acetyltransferase gene under the control of the HIV-1 LTR. The protein kinase C inhibitors curcumin and staurosporine, but not a tyrosine kinase inhibitor herbimycine A, inhibited Tat-mediated LTR-driven transactivation. Two antimalarial drugs quinacrine and chloroquine, that are also arachidonic acid metabolism inhibitors, were found to inhibit the Tat-mediated LTR-driven gene expression. Another inhibitor of arachidonic acid metabolism 4-bromophenacyl bromide was also found to inhibit Tat-mediated gene expression driven by HIV-1 LTR. However, the antimalarial drug quinine elicited no effects on Tat-mediated transactivation. These results suggest that the anti-arachidonic acid metabolism properties of quinacrine and chloroquine may be responsible for their ability to inhibit Tat-mediated LTR-regulated gene expression.

Pharmacologic study of basophil histamine release induced by monocyte chemotactic protein-1 with kinase inhibitors

Monocyte chemotactic protein-1 (MCP-1)/monocyte chemotactic activating factor has a potent histamine-releasing activity for basophils and is a major component of IgE-independent histamine-releasing factors (HRF). In this study, we examined the effect of a panel of kinase inhibitors on MCP-1-induced histamine release from human basophils to characterize the signaling pathway used by this chemokine. Genistein (3 micrograms/ml), an inhibitor of tyrosine kinase, inhibited MCP-1-induced histamine release by 44%. Wortmannin is a specific inhibitor of phosphatidylinositol 3 kinase (PI-3 kinase). It blocked MCP-1-induced histamine release with an IC50 of 3.3 x 10(-8) M indicating a role of PI-3 kinase in this reaction. KT5926, an inhibitor of myosin light chain kinase, also inhibited histamine release in response to MCP-1 with an IC50 of 10(-6) M. Staurosporine, a potent inhibitor of protein kinase C, although being not specific, augmented MCP-1-induced histamine release by 31.9% at 10(-6) M. These results indicate the possible involvement of a series of kinases, including PI-3 kinase, in the signal transduction pathway used by MCP-1.

No prevention of ischemic preconditioning by the protein kinase C inhibitor staurosporine in swine

The delay of infarct size development by ischemic preconditioning involves the activation of protein kinase C in rats and rabbits. In dogs the role of protein kinase C in ischemic preconditioning is controversial. We investigated whether or not the activation of protein kinase C is a prerequisite for ischemic preconditioning in swine. Swine were used, since they are large mammals and since infarct development in this species, due to the lack of an innate collateral circulation, is similar to that in humans. In 20 enflurane-anesthetized swine, the proximal left anterior descending coronary artery was cannulated and perfused from an extracorporeal circuit. The impact of continuous intracoronary infusion of 10(-7) mol/L staurosporine, a potent protein kinase C inhibitor, on global and regional myocardial function (sonomicrometry), subendocardial blood flow (ENDO, microspheres), and infarct size (IS, triphenyltetrazolium chloride staining after 120 minutes of reperfusion) was analyzed. Staurosporine (10(-7) mol/L) abolished the 1.6-fold increase in coronary arterial resistance in response to 10(-6) mol/L IC 4 beta-phorbol 12-myristate 13-acetate, a potent protein kinase C activator. In the presence of staurosporine, 90 minutes of low-flow ischemia at an ENDO of 0.05 +/- 0.04 (mean +/- SD) mL.min-1.g-1 resulted in an IS of 12.5 +/- 8.6% (n = 10) of the area at risk. Also, in the presence of staurosporine, ischemic preconditioning by a cycle of 10 minutes of low-flow ischemia followed by 15 minutes reperfusion before the 90 minutes sustained ischemic period (ENDO, 0.05 +/- 0.03 mL.min-1.g-1) reduced IS to 3.3 +/- 3.4% (n = 10, P < .05). The protein kinase C inhibitor staurosporine does not prevent ischemic preconditioning in swine.

Tumor necrosis factor alpha (TNFalpha) induces pro-matrix metalloproteinase 9 production in human uterine cervical fibroblasts but interleukin 1alpha antagonizes the inductive effect of TNFalpha

We have examined the regulation of precursor of matrix metalloproteinase 9 (proMMP-9)/progelatinase B production by tumor necrosis factor alpha (TNFalpha) and interleukin 1alpha (IL-1alpha) using human uterine cervical fibroblasts. TNFalpha, but not IL-1alpha, induces the production of proMMP-9 in the cervical cells. IL-alpha, however, suppresses the TNFalpha-induced proMMP-9 production. 12-0-tetradecanoylphorbol 13-acetate (TPA) also stimulates the cervical cells to produce proMMP-9, and IL-1alpha synergistically enhances its production. TNFalpha-induced proMMP-9 production is not mediated by protein kinase C (PKC), whereas the effect of IL-1alpha is through PKC. By contrast, proMMP-3/prostromelysin 1 is up-regulated by TNFalpha or TPA in the presence of IL-1alpha, whose modulation is PKC-dependent. The suppressive effect of IL-1alpha on the TNFalpha-induced proMMP-9 production is a new biological effect of IL-1 on MMP production.

Phenobarbital induction of cytochrome P4501A1 is regulated by cAMP-dependent protein kinase-mediated signaling pathways in rainbow trout hepatocytes

Phenobarbital (PB) induces CYP1A1 at the transcriptional level and causes nuclear translocation of the aromatic hydrocarbon (Ah) receptor in primary cultures of rainbow trout hepatocytes (1). The results from this study suggest that PB induction of CYP1A1 in rainbow trout hepatocytes is regulated by cAMP-dependent pathways (PKA), whereas TCDD induction is not dependent upon PKA. Epinephrine, which increases cAMP levels and activates PKA-dependent pathways, was a potent inhibitor of PB induction, while having no effect on TCDD induction of CYP1A1 gene expression. When PKA-dependent pathways were inhibited, PB induction of CYP1A1 gene expression was greatly potentiated, whereas TCDD induction was affected to a lesser extent. Inhibitors of calcium-phospholipid-dependent protein kinase (PKC) had modest or no effect on PB and TCDD induction of CYP1A1, respectively. Whether the relatively weak-to-no inhibition of CYP1A1 in response to PKC inhibitors in fish is due to differences in the types and levels of PKC isoenzymes, cell permeability, protocol, or the role of PKC in the mechanism of CYP1A1 induction in fish remains to be established. PB induced persistent and transient increases in the intracellular calcium concentration. This may be an important factor regulating PKC which may have a role in PB-mediated induction of CYP1A1 gene transcription.

Modulation of human muscle sodium channels by intracellular fatty acids is dependent on the channel isoform

Free fatty acids (FFAs), including arachidonic acid (AA), are implicated in the direct and indirect modulation of a spectrum of voltage-gated ion channels. Skeletal muscle sodium channels can be either activated or inhibited by FFA exposure; the response is dependent on both FFA structure and site of exposure. Recombinant human skeletal muscle sodium channels (hSkM1) were transfected into heterologous human renal epithelium HEK293t cells. Cytoplasmic delivery of 5 microM AA augmented the voltage-activated sodium current of hSkM1 channels by 190% (+/-54 S.E., n = 7) over a 20-min period. Similar results were seen with 5 microM oleic acid. Sodium currents in HEK293t cells transfected with human cardiac muscle sodium channels (hH1) were insensitive to AA treatment, and exposure to oleic acid inhibited the hH1 currents over a 20-min period by 29% (+/-13 S.E., n = 5). The increase in hSkM1 current was not accompanied by shifts in voltage dependence of activation, steady-state inactivation, or markedly altered kinetics of inactivation of the macroscopic current. The FFA-induced increase in sodium currents was not dependent on protein kinase C activity. In contrast, both isoforms were reversibly inhibited by external application of unsaturated FFA. Thus, the differential effects of FFA on skeletal muscle sodium channels first noted in cultured muscle cells can be reproduced by expressing recombinant sodium channels in epithelial cells. Although the responses to applied FFAs could be direct or indirect, we suggest that: 1) SkM1 has two classes of response to FFA, one which produces augmentation of macroscopic currents with intracellular FFA, and a second which produces inhibition with extracellular FFA; 2) H1 has only one class of response, which produces inhibition with extracellular FFA. A testable hypothesis is that the presence or absence of each response is due to a specific structure in SkM1 or H1. These specific structures may directly interact with FFA or may interact with intermediate components.

Induction of apoptosis in prostatic tumor cell line DU145 by staurosporine, a potent inhibitor of protein kinases

We are interested in studying the possibility of modulating prostatic cell growth by manipulating apoptosis. Here we show that 1 microM staurosporine (STS) induces a human androgen-independent prostatic tumor cell line, DU145, to undergo dramatic changes in morphology and results in programmed cell death. Several genes involved in apoptosis were analyzed for expression in STS-treated and untreated DU145 cells. It was observed that these genes were differentially regulated. The expression level of bcl-2, bcl-xL, Ich-1L remains unchanged in treated and untreated cells. On the other hand, DAD1 and interleukin-1 beta-converting enzyme (ICE) were downregulated while bcl-xs and Ich-1s were upregulated. By blocking bcl-2 gene expression using antisense oligonucleotides, it was determined that the anti-bcl-2 oligonucleotides have no effect on the proliferation of DU145 or STS-treated DU145 cells. These results demonstrate that programmed cell death can be induced in an androgen-independent prostatic cancer cell line and BCL-2 was found not to play an important role in preventing STS-induced apoptosis in the DU145 cell line.

Protein kinase C-induced contraction is inhibited by halothane but enhanced by isoflurane in rat coronary arteries

Protein kinase C (PKC), important in signal transduction, may help generate and maintain vascular smooth muscle tone. We sought to examine the effect of the volatile anesthetics isoflurane and halothane on PKC agonist-induced vasoconstriction and PKC inhibitor-induced vasorelaxation. Subepicardial resistance arteries were dissected from rat hearts. Changes in vessel diameters were monitored in response to the membrane-bound PKC agonist 12-deoxyphorbol-13-isobutyric-20-acetate (PBE) 10(-8)-10(-7) M or the cytosolic PKC agonist oleic acid 10(-7)-10(-5.5) M either in the presence of isoflurane 1.15%, isoflurane 2.3%, halothane 0.77%, halothane 1.54%, or no volatile anesthetics (control). In addition, after preconstriction with the thromboxane analog U46619 1 microM, relaxation responses to the PKC inhibitor staurosporine 10(-8)-10(-7) M were examined in the presence or absence of the anesthetics as above. PBE-induced constriction was attenuated by either concentration of halothane (P < 0.05) but was unaltered by isoflurane (P > 0.5). Oleic acid-induced constriction was abolished by halothane (P < 0.001) but enhanced by isoflurane (P < 0.01). Staurosporine-induced relaxation of U46619-preconstricted vessels was attenuated by isoflurane (P < 0.05) but unaltered by halothane (P > 0.3). We conclude that isoflurane may enhance cytosolic PKC-mediated vasoconstriction, whereas halothane may attenuate both cytosolic and membrane-bound PKC-mediated vasoconstriction.

Regulation of epithelial Na+ permeability by protein kinase C is tissue specific

Protein kinase C (PKC) is a major regulator of a broad range of cellular functions. Activation of PKC has been reported to stimulate Na+ transport across frog skin epithelium by increasing the apical Na+ permeability. This positive natriferic response has not been observed with other epithelial preparations, and could reflect the specific experimental conditions of different laboratories, or species or organ specificity of the response to PKC. In the present study, measurements were conducted with skins and urinary bladders from the same animals of two different species. The PKC activator TPA uniformly increased the transepithelial Na+ transport (measured as amiloride-sensitive short-circuit current, ISC, across skins from Rana temporaria and Bufo marinus, and inhibited ISC across bladders from the same animals. Inhibitors of PKC (staurosporine, H-7 and chelerythrine) partially blocked the TPA-induced stimulation of ISC across frog skin. The specificity of the PKC response by amphibian skin could have reflected an induction of moulting, similar to that observed with aldosterone. However, light micrographs of paired areas of frog skin revealed no evidence of the putative moulting. Separation of stratum corneum from the underlying stratum granulosum could be detected following application of aldosterone. We conclude that the effect of PKC on epithelial Na+ channels is organ, and not species specific. The stimulation of Na+ permeability in amphibian skin does not arise from sloughing of the stratum corneum. These observations are consistent with the hypothesis that the natriferic action arises from the calcium-independent isozyme of PKC previously detected in frog skin.

A brief staurosporine treatment of mitotic cells triggers premature exit from mitosis and polyploid cell formation

At any point during the progression of many tumor types, cells can develop a hyperploid DNA content. Hyperploid tumors are significant more aggressive, with a higher growth rate and a poor patient prognosis. Yeast genetics have implicated three important genes involved in DNA ploidy changes: cdc2, cyclin b, and a specific inhibitor of the p34(cdc2)/cyclin B kinase, rum1. Mutations in these genes uncoupled the dependence mitosis on DNA replication in the fission yeast, Saccharomyces pombe. It was proposed that the inactivation of the mitotic kinase complex, p34(cdc2)/cyclin B, induces a G(1), state wherein the cells re-replicate their DNA without an intervening mitosis. We show in this report that treatment of only M phase-arrested mouse cells, with the protein kinase inhibitor staurosporine, induced polyploidy. Nocodazole-arrested metaphase FT210 cells were pulsed with 100 ng/ml of staurosporine for 1 h. This 1-h treatment results in the inhibition of the mitotic p34(cdc2) kinase. The inhibition of the mitotic kinases leads to a reduction in the histone H1 and H3 mitotic-associated phosphorylations, chromosome decondensation and nuclear membrane reformation. When released into normal growth medium, these cells are reset to a G(1)state, re-replicate their DNA without completing mitosis, and become octaploid.

Amplitude-dependent modulation of brush border enzymes and proliferation by cyclic strain in human intestinal Caco-2 monolayers

Little is known about the effects of repetitive deformation during peristaltic distension and contraction or repetitive villus shortening on the proliferation and differentiation of the intestinal epithelium. We sought to characterize the effects of repetitive deformation of a physiologically relevant magnitude and frequency on the proliferation and differentiation of human intestinal epithelial Caco-2 cells, a common cell culture model for intestinal epithelial biology. Human intestinal epithelial Caco-2 cells were cultured on collagen-coated membranes deformed by -20 kPa vacuum at 10 cycles/minute, producing an average 10% strain on the adherent cells. Proliferation was assessed by cell counting and 3H-thymidine incorporation. Alkaline phosphatase and dipeptidyl dipeptidase specific activity were measured in cell lysates. Since cells at the membrane periphery experience higher strain than cells in the center, the topography of brush border enzyme histochemical and immunohistochemical staining was analyzed for strain-dependence. Cyclic strain stimulated proliferation compared to static cells. Proliferation was highest in the membrane periphery where strain was maximal. Strain also modulated differentiation independently of its mitogenic effects, selectively stimulating dipeptidyl dipeptidase while inhibiting alkaline phosphatase. Strain-associated enzyme changes were also maximal in areas of greatest strain. The PKC inhibitors staurosporine and calphostin C ablated strain mitogenic effects while intracellular PKC activity was increased by strain. The strain-associated brush border enzyme changes were attenuated but not blocked by PKC inhibition. Thus, strain of a physiologically relevant frequency and magnitude promotes proliferation and modulates the differentiation of a well-differentiated human intestinal epithelial cell line in an amplitude-dependent fashion. PKC may be involved in coupling strain to increased proliferation.

Amplitude-dependent modulation of brush border enzymes and proliferation by cyclic strain in human intestinal Caco-2 monolayers

Little is known about the effects of repetitive deformation during peristaltic distension and contraction or repetitive villus shortening on the proliferation and differentiation of the intestinal epithelium. We sought to characterize the effects of repetitive deformation of a physiologically relevant magnitude and frequency on the proliferation and differentiation of human intestinal epithelial Caco-2 cells, a common cell culture model for intestinal epithelial biology. Human intestinal epithelial Caco-2 cells were cultured on collagen-coated membranes deformed by -20 kPa vacuum at 10 cycles/minute, producing an average 10% strain on the adherent cells. Proliferation was assessed by cell counting and 3H-thymidine incorporation. Alkaline phosphatase and dipeptidyl dipeptidase specific activity were measured in cell lysates. Since cells at the membrane periphery experience higher strain than cells in the center, the topography of brush border enzyme histochemical and immunohistochemical staining was analyzed for strain-dependence. Cyclic strain stimulated proliferation compared to static cells. Proliferation was highest in the membrane periphery where strain was maximal. Strain also modulated differentiation independently of its mitogenic effects, selectively stimulating dipeptidyl dipeptidase while inhibiting alkaline phosphatase. Strain-associated enzyme changes were also maximal in areas of greatest strain. The PKC inhibitors staurosporine and calphostin C ablated strain mitogenic effects while intracellular PKC activity was increased by strain. The strain-associated brush border enzyme changes were attenuated but not blocked by PKC inhibition. Thus, strain of a physiologically relevant frequency and magnitude promotes proliferation and modulates the differentiation of a well-differentiated human intestinal epithelial cell line in an amplitude-dependent fashion. PKC may be involved in coupling strain to increased proliferation.

Interleukin-1beta activates protein kinase C zeta in renal mesangial cells. Potential role in prostaglandin E2 up-regulation

Protein kinase C (PKC) plays a role in signal transduction mediated by interleukin-1beta (IL-1beta) leading to the increase in prostaglandin E2 (PGE2) production. In the present study we suggest that there are at least two distinct PKC isotypes involved in the signaling mechanism. Staurosporine potentiated the effect of IL-1beta on coxII mRNA expression while calphostin C totally inhibited mRNA expression. The down-regulation of PKC by growing mesangial cells in the presence of phorbol 12-myristate 13-acetate for 24 h failed to modify the up-regulated response in PGE2 formation by IL-1beta. Furthermore, incubation of mesangial cells with IL-1beta causes translocation of PKCzeta from cytosol to a presumed membrane compartment, and this translocation phenomenon was not inhibited by incubating the cells with staurosporine but was inhibited with calphostin C. Gel retardation assays also demonstrated that staurosporine did not inhibit the IL-1beta-stimulated binding of nuclear extracts to the NFkappaB motif. In contrast, calphostin C inhibited binding to the kappaB motif in a dose-dependent manner. Finally, antisense oligonucleotides to PKCzeta partially inhibited the IL-1beta-induced PGE2 formation while control sense oligonucleotides were without effect. Taken together, these data suggest that PKCzeta is involved in the IL-1beta signaling responses.

Tumor necrosis factor alpha-induced vascular leakage involves PECAM1 phosphorylation

Herein we show that exposure of human umbilical vein endothelial cells to tumor necrosis factor alpha (TNFalpha) led to platelet endothelial cell adhesion molecule-1 (PECAM1) surface redistribution, disruption of cytoskeleton connections, and increased PECAM1 phosphorylation, accompanied by increased permeability to macromolecules. The in vitro use of inhibitors of tyrosine or serine-threonine kinases could prevent both PECAM1 surface redistribution and the increase in permeability induced by the cytokine. In vivo administration of lavendustin A, a natural tyrosine kinase inhibitor, protected endothelial cells from TNFalpha-dependent vascular leakage in mouse liver. We propose that the involvement of PECAM1 in TNFalpha-mediated effects on vascular permeability may depend on a dynamically regulated cytoskeletal association, related to the degree of PECAM1 phosphorylation.

Coronary artery spasm does not depend on the intracellular calcium store but is substantially mediated by the protein kinase C-mediated pathway in a swine model with interleukin-1 beta in vivo

BACKGROUND

The intracellular mechanism for coronary artery spasm is still unknown. Since the protein kinase C (PKC)-mediated pathway and Ca2+ release from sarcoplasmic reticulum (SR) are important intracellular mechanisms of vascular smooth muscle contraction, we examined the possible role of these two mechanisms in the pathogenesis of coronary spasm in our swine model in vivo.

METHODS AND RESULTS

In 25 pigs, interleukin-1 beta (IL-1 beta) was applied chronically to the coronary arteries from the adventitia to induce an inflammatory/proliferative lesion. Two weeks after the operation, either intracoronary serotonin or histamine repeatedly induced coronary spasm at the IL-1 beta-treated site. At those spastic sites, phorbol-12, 13-dibutyrate, a PKC-activating phorbol ester, also induced coronary spasm, which was blocked by pretreatment with the PKC inhibitors staurosporine and sphingosine. Serotonin- and histamine-induced coronary spasm was also significantly inhibited by pretreatment with staurosporine, sphingosine, or nifedipine (an L-type Ca2+ channel antagonist) but not by ryanodine (an inhibitor of Ca(2+)-induced Ca2+ release from SR) or thapsigargin (an inhibitor of Ca(2+)-ATPase of SR). Bay K 8644 (an L-type Ca2+ channel agonist) also induced coronary spasm at the IL-1 beta-treated site, which was significantly inhibited by pretreatment with staurosporine, sphingosine, and nifedipine. In contrast, coronary vasoconstriction induced by prostaglandin F2 alpha was not affected by pretreatment with staurosporine or sphingosine but was significantly inhibited by pretreatment with ryanodine, thapsigargin, or nifedipine.

CONCLUSIONS

These results suggest that (1) PKC activation largely accounts for the serotonin- and histamine-induced coronary spasm; (2) at the spastic site, the calcium influx through L-type Ca2+ channels may be augmented via the PKC-mediated pathway; and (3) the Ca2+ release from the SR into the cytosol may not play a primary role in coronary spasm.

The CED-3/ICE-like protease Mch2 is activated during apoptosis and cleaves the death substrate lamin A

Phylogenetic analysis of the CED-3/ICE family of cysteine proteases suggests the existence of a subfamily most related to the Caenorhabditis elegans death gene ced-3 and includes Yama (CPP32, apopain), LAP3 (Mch3, CMH1), and Mch2. Here, we show that Mch2 is processed from its zymogen form to a proteolytically active dimeric species during execution of the apoptotic program and by the cytotoxic T cell death protease granzyme B. Additionally, like Yama and LAP3, Mch2 functions downstream of the death inhibitors Bcl-2, Bcl-xL, and CrmA. Importantly, Mch2, but not Yama or LAP3, is capable of cleaving lamin A to its signature apoptotic fragment, indicating that Mch2 is an apoptotic laminase.

Interphase and M-phase oral KB carcinoma cells are targetted in staurosporine-induced apoptosis

The effect of staurosporine, an antimicrobial agent and inhibitor of protein kinase C (PKC) on programmed cell death/apoptosis (PCD) was investigated in the human oral cavity epidermoid carcinoma KB cell line. Staurosporine-treated oral KB carcinoma cells exhibited morphological features characteristic of apoptosis such as (a) cell shrinkage and increased nuclear fluorescence (quantitated by image analysis with laser scanning confocal microscopy), (b) nuclear condensation and fragmentation observed under fluorescence microscopy with propidium-iodide-DNA staining and (c) chromatin condensation seen under transmission electron microscopy. Specific terminal deoxynucleotidyl transferase (TdT)-mediated labeling of 3'OH ends of DNA breaks in staurosporine-treated cells confirmed DNA fragmentation. In addition, we show the concomitant existence of M-phase PCD with interphase PCD in staurosporine-treated KB cells. It would appear that staurosporine induces apoptosis regardless of the cell cycle phase and that mitosis and apoptosis are not necessarily mutually exclusive events.

Ca2+ entry induced by calcium influx factor and its regulation by protein kinase C in rabbit neutrophils

Extracellular application of acid extract from platelet-activating factor- or thapsigargin-treated rabbit neutrophils induced a rise of cytosolic free calcium concentration ([Ca2+]i) in neutrophils and adrenal chromaffin cells suspended in Ca(2+)-containing, but not in Ca(2+)-deficient, medium. The ability of the extract to selectively induce Ca2+ entry was also confirmed by the increase in 45Ca2+ uptake and failure to stimulate Ca2+ release in digitonin-permeabilized neutrophils. 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibited the extract-induced [Ca2+]i rise in a staurosporine (ST)-sensitive fashion, neither of which had any effect on its production. SK&F 96365 and econazole also reduced extract-induced Ca2+ entry. These results suggest that a Ca2+ entry-inducible substrate (calcium influx factor) is extracted from Ca2+ store-depleted neutrophils, and that its action may be regulated by protein kinase C and certain pharmacological agents.

Heat shock protein 27 blocks Fas/APO-1- and staurosporine-induced cell death

Small stress protein expression enhances the survival of mammalian cells exposed to numerous injuries that induce necrotic cell death. The cell surface receptor Fas/APO-1 and its ligand have been recently identified as important mediators of apoptosis. Here, we show that constitutive expression of human heat shock protein (hsp)27 in murine L929 cells blocks Fas/APO-1-mediated cell death. Expression of human hsp27 prevented anti-APO-1-induced DNA fragmentation and morphological changes. These results strongly suggest that human hsp27 acts as a cellular inhibitor of Fas/APO-1-induced apoptosis. We also report that the expression of small stress proteins from different species, such as human hsp27, Drosophila Dhsp27, or human alphaB-crystallin, confers resistance to apoptotic cell death induced by staurosporine, a protein kinase C inhibitor. Hence, small stress proteins are novel regulators that are able to block apoptosis induced by different pathways.

Role of calcium in nitric oxide-mediated injury to rat gastric mucosal cells

BACKGROUND & AIMS

Perturbations in Ca2+ homeostasis as well as high levels of nitric oxide have been associated with gastric cellular injury. The purpose of this study was to examine whether high levels of endogenous or exogenous NO damage gastric cells by altering intracellular Ca2+.

METHODS

Epithelial cells were isolated from the rat stomach, and cell integrity was estimated by trypan blue exclusion and alamar blue dye absorption. Cytosolic intracellular Ca2+ concentrations ([Ca2+]i) were determined by indo-1 dye fluorescence. NO synthase activity was assessed radioenzymatically.

RESULTS

Induction of Ca2+-independent NO synthase in response to endotoxin challenge resulted in decreased viability and an increase in [Ca2+]i in gastric mucosal cells. These responses were ameliorated by pretreatment with NG-nitro-L-arginine methyl ester or dexamethasone. Treatment of cells with the NO donor S-nitrosoacetyl-penicillamine also decreased cell integrity and increased [Ca2+]i. The actions of S-nitroso-acetyl-penicillamine could be reduced by decreasing intracellular or extracellular Ca2+, by chelating Ca2+ with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid or 1,2,-bis(2-aminophenoxy)ethane-N,N,N,N'-tetraacetic acid acetoxymethyl ester, by Ca2+ channel antagonism (nifedipine), or by displacing surface-bound Ca2+ (lanthanum). Furthermore, cell damage was reduced by inhibiting protein kinase C activity with either H-7 or staurosporine.

CONCLUSIONS

Excessive levels of NO from either endogenous or exogenous sources results in a reduction in gastric cellular viability. This response seems to be related causally to an increase in [Ca2+]i and protein kinase C activation.

GH inhibition of lipogenesis and stimulation of lipolysis in sheep adipose tissue: involvement of protein serine phosphorylation and dephosphorylation and phospholipase C

The intracellular signalling systems involved in the chronic insulin-antagonistic, anti-lipogenic effects and also the lipolytic effect of GH have been investigated in sheep adipose tissue in an in vitro tissue culture system. During culture, chronic exposure to GH decreased the rate of lipogenesis and prevented the increase in lipogenesis induced by insulin. GH also increased glycerol release into the culture medium. GH had no acute, insulin-like effect on lipogenesis in sheep adipose tissue. Pretreatment with phorbol ester to down-regulate isoforms of protein kinase C or addition of the protein serine kinase inhibitor staurosporine decreased the anti-lipogenic effect of GH while the protein serine kinase inhibitor H7 eliminated it completely. Pretreatment with phorbol ester or addition of H7 also decreased the insulin-antagonistic effect of GH on lipogenesis. Addition of the protein serine phosphatase inhibitor okadaic acid or the phosphatidyl choline phospholipase C inhibitor D609 both diminished the anti-lipogenic and insulin-antagonistic effects of GH. Chronic exposure of adipose tissue to GH had no effect on the total activity of acetyl CoA carboxylase or its activation status but it did diminish the increase in activation status induced by insulin. H7 and okadaic acid also diminished the increase in activation status of acetyl CoA carboxylase induced by insulin but did not alter the effect of GH on this variable. Okadaic acid decreased total acetyl CoA carboxylase activity. Pretreatment with phorbol ester or the addition of H7, staurosporine or okadaic acid increased glycerol release into the culture medium to the same extent as GH itself; the effects of GH and these various agents were not additive. These studies suggest that the anti-lipogenic, insulin-antagonistic effects of GH involve both protein serine kinases and phosphatases, possibly including one or more isoforms of protein kinase C, and a phosphatidyl choline-specific phospholipase C. Comparison with studies by others on the GH enhancement of preadipocyte differentiation and prolactin stimulation of lipogenesis in mammary tissue suggests involvement of protein kinase C at an early stage in all three systems. In contrast, effects of okadaic acid vary with the system, suggesting the involvement of protein serine phosphatase activity in a late stage of the action of GH. The effects of GH on lipogenesis and lipolysis do not occur via identical mechanisms.

Decreased accumulation and dephosphorylation of the mitosis-specific form of nucleophosmin/B23 in staurosporine-induced chromosome decondensation

Nucleophosmin/B23 is highly phosphorylated by cdc2 kinase during mitosis, and this phosphorylation most probably has a role in initiating and controlling the entry of cells into mitosis [Peter, Nakagawa, Doree, Labbe and Nigg (1990) Cell 60, 791-801]. In the present study, the protein kinase inhibitor staurosporine has been used to examine possible changes in nucleophosmin/B23 at mitosis in HeLa cells. Addition of staurosporine to HeLa cells already arrested at mitosis by nocodazole causes: (i) decreased accumulation of the mitosis-specific form of nucleophosmin/B23, (ii) dephosphorylation of nucleophosmin/ B23, (iii) redistribution of nucleophosmin/B23 to the cytosol, and (iv) concomitant decondensation of chromosomes. These results suggest that the mitosis-specific phosphorylated form of nucleophosmin/B23 may play a role in maintaining mitotic chromosomes in their condensed state.

Thrombin induces proliferation of osteoblast-like cells through phosphatidylcholine hydrolysis

We examined the effect of thrombin on phosphatidylcholine-hydrolyzing phospholipase D activity in osteoblast-like MC3T3-E1 cells. Thrombin stimulated the formation of choline dose dependently in the range between 0.01 and 1 U/ml, but not the phosphocholine formation. Diisopropylfluorophosphate (DFP)- inactivated thrombin had little effect on the choline formation. The combined effects of thrombin and 12-O-tetradecanoylphorbol-13-acetate, a protein kinase C-activating phorbol ester, on the choline formation were additive. Staurosporine, an inhibitor of protein kinases, had little effect on the thrombin-induced formation of choline. Combined addition of thrombin and NaF, an activator of heterotrimeric GTP-binding protein, did not stimulate the formation of choline further. Pertussis toxin had little effect on the thrombin-induced formation of choline. Thrombin stimulated Ca2+ influx from extracellular space time and dose dependently. The depletion of extracellular Ca2+ by EGTA exclusively reduced the thrombin-induced choline formation. Thrombin had only a slight effect on phosphoinositide-hydrolyzing phospholipase C activity. Thrombin induced diacylglycerol formation and DNA synthesis, and increased the number of MC3T3-E1 cells, but DFP-inactivated thrombin did not. Thrombin suppressed both basal and fetal calf serum-induced alkaline phosphatase activity in these cells. Propranolol, an inhibitor of phosphatidic acid phosphohydrolase, inhibited both the thrombin-induced diacylglycerol formation and DNA synthesis. These results suggest that thrombin stimulates phosphatidylcholine-hydrolyzing phospholipase D due to self-induced Ca2+ influx independently of protein kinase C activation in osteoblast-like cells and that its proliferative effect depends on phospholipase D activation.

Differential effects of kinase inhibitors on erythropoietin and vascular endothelial growth factor gene expression in rat hepatocytes

This study sought to investigate whether a common protein kinase activity is involved in the sequence of events by which oxygen controls the expression of the genes for erythropoietin (EPO) and for vascular endothelial growth factor (VEGF) in rat hepatocytes. To this end we examined the influence of the non-specific kinase inhibitor staurosporine and of the tyrosine kinase inhibitor genistein on EPO and VEGF mRNA levels in primary cultures of rat hepatocytes kept at either high (20% O2) or low (1% O2) oxygen tension. We found that 3 h of exposure to the low O2 tension increased EPO mRNA levels about 20-fold and the three VEGF (-180, -164, -120) mRNA levels, on average, about fourfold. Staurosporine did not change EPO and VEGF mRNA levels at 20% O2, but in a concentration-dependent manner, decreased EPO and VEGF mRNA at 1% O2 with IC50 values of 30 nM and 1000 nM, respectively. In the presence of 1% O2, genistein decreased EPO mRNA and VEGF mRNA levels with IC50 values of about 36 and 360 microM, respectively. Although mRNA levels for glycerine aldehyde phosphatehydrogenase (GAPDH) were not changed, staurosporine and genistein inhibited uridine incorporation into total RNA with IC50 values of about 1 microM and 100 microM, respectively. Comparison with the transcription inhibitor actinomycin D suggested that the effects of both kinase inhibitors on VEGF mRNA but not on EPO mRNA levels could be attributed to the non-specific inhibition of transcription in hepatocytes. These findings suggest that a kinase activity is specifically involved in the O2-dependent control of EPO gene expression but not of VEGF gene expression in hepatocytes.

BCL-2 and MCL-1 expression in Chinese hamster ovary cells inhibits intracellular acidification and apoptosis induced by staurosporine

Multiple physiological and pharmacological stimuli induce cells to die by apoptosis. In many cases, this apoptosis is inhibited by BCL-2, suggesting the involvement of a common regulatory pathway. One frequent characteristic of apoptosis is the digestion of DNA into oligonucleosome-length fragments. Intracellular acidification and increased intracellular calcium have been variously implicated in activating the endonuclease responsible for this DNA digestion. To explore the involvement of these potential signals in endonuclease activation, we have analyzed three Chinese hamster ovary cell lines: a parental line, one expressing a cDNA encoding BCL-2, and the third expressing the BCL-2 family member MCL-1. Apoptosis was induced with the protein kinase inhibitor staurosporine and intracellular pH and calcium were measured by flow cytometry. We found that both MCL-1 and BCL-2 inhibited DNA digestion compared to the parent cell line, although BCL-2 was more potent in this regard. Concurrent with DNA digestion, we observed intracellular acidification; MCL-1 and BCL-2 inhibited intracellular acidification to an extent commensurate with their ability to inhibit DNA digestion. In contrast, staurosporine caused a dose-dependent increase in intracellular calcium in all three cell lines, demonstrating that intracellular free calcium levels did not correlate with the induction of apoptosis. These results suggest that BCL-2 and MCL-1 may regulate a pathway for intracellular pH homeostasis during apoptotic cell death.