Stenocereus huastecorum-fruit juice concentrate protects against cisplatin-induced nephrotoxicity by nitric oxide pathway activity and antioxidant and antiapoptotic effects.

Cisplatin (CP) is an antineoplastic agent used to treat solid tumors, that has high nephrotoxicity caused by physiologic, hemodynamic, and biochemical alterations. Some studies have shown that naturally derived bioactive compounds in CP-induced nephrotoxicity reduce the side effects of this antineoplastic drug. Pitaya is an endemic fruit from Mexico with a high bioactive compound content, including betalains and phenolic compounds, with reports of antioxidant and anti-inflammatory properties. In this study, the aim was to establish the effect of a pitaya juice concentrate (PJC) on CP-induced nephrotoxicity in Wistar male rats through the identification of metabolites, determination of its chemical composition and antioxidant activity, and evaluation of the protective effect of a PJC on CP-induced nephrotoxicity in rats. The PJC showed a high content of betanins with antioxidant activity by an oxygen radical absorbance capacity assay (1299.6 ± 2.80 Trolox equivalents/g). PJC was administered daily (400 mg day-1, p. o.) for 3 days before CP administration until the end of the experiment. On day four, rats were administered a single injection of CP (6 mg kg, i.p.-1) and sacrificed 72 h later. We observed that CP provoked renal dysfunction (1.0 ± 0.1 vs. 0.4 ± 0.07 serum creatinine levels), oxidative stress, a decrease in nitrate and nitrite (NO2¯/NO3¯) levels (0.1 ± 0.08 vs. 0.4 ± 0.3) and activation of apoptosis and immune responses in kidney tissue. In addition, CP treatment induced tubular damage threefold. PJC administration prevented renal dysfunction (0.5 ± 0.06 vs. 1.0 ± 0.1), normalized degenerative structural damage prevented the increase in lipoperoxidation levels (0.04 ± 0.01 vs. 0.2 ± 0.1) and reduced the apoptosis index by 2.5 in kidney tissue. However, it did not modify the immune response caused by CP. Furthermore, PJC treatment increased nuclear factor erythroid two related factors two protein levels two times and NO2¯/NO3¯ levels 22 times in kidney tissue, which may play a role in the renoprotective effect. In conclusion, the renoprotective effect of PJC on CP-induced nephrotoxicity was associated with the attenuation of dysfunction, structural damage, apoptosis activation, and oxidative stress and was related to changes in the tumor necrosis factor-alpha and renal nitric oxide (NO) pathways. The changes in the NO pathway may be involved in renal hemodynamics. Pitaya could be used as a functional food and therapeutic coadjuvant during CP treatments due to its high bioactive levels and renoprotective compounds.

The influence of yeast on chemical composition and sensory properties of dry white wines.

This study evaluates the impact on two varietal white wines from 'Chardonnay' and 'Verdejo' cultivars of different fermentative strategies: inoculation with Saccharomyces cerevisiae yeast (CT), sequential inoculation (Torulaspora delbrueckii/Saccharomyces cerevisiae) (SI), and spontaneous fermentation (SP). The wines' chemical composition was characterized by oenological parameters, organic acids, metals, major volatile compounds, ester compounds and sensory analyses. The fermentative strategy (CT, SI and SP) was found to be a key factor for assessing different styles of white wines. SI wines showed enhanced 'mature fruit' nuances and a chemical profile characterized by higher content of ethyl propanoate, ethyl isobutyrate and ethyl dihydrocinnamate. Meanwhile, the SP wines presented enhanced "stone fruit" nuances possible related to the higher contents of 2-phenyl acetate and isobutyl acetate. After a chemometric approach the above esters were identified as the markers of each fermentative strategy, independently of the variety.

Provenance effect on carbon assimilation, photochemistry and leaf morphology in Mediterranean Cistus species under chilling stress.

The potential resilience of shrub species to environmental change deserves attention in those areas threatened by climate change, such as the Mediterranean Basin. We asked if leaves produced under different climate conditions through the winter season to spring can highlight the leaf traits involved in determining potential resilience of three Cistus spp. to changing environmental conditions and to what extent intraspecific differences affect such a response. We analysed carbon assimilation, maximum quantum efficiency of PSII photochemistry (Fv /Fm ) and leaf morphological control of the photosynthetic process in leaves formed through the winter season into spring in C. creticus subsp. eriocephalus (CE), C. salvifolius (CS) and C. monspeliensis (CM) grown from seed of different provenances under common garden conditions. Intraspecific differences were found in Fv /Fm for CE and CS. Carbon assimilation-related parameters were not affected by provenance. Moreover, our analysis highlighted that the functional relationships investigated can follow seasonal changes and revealed patterns originating from species-specific differences in LMA arising during the favourable period. Cistus spp. have great ability to modify the structure and function of their leaves in the mid-term in order to cope with changing environmental conditions. The Fv /Fm response to chilling reveals that susceptibility to photoinhibition is a trait under selection in Cistus species. Concerning carbon assimilation, differing ability to control stomatal opening was highlighted between species. Moreover, seasonal changes of the functional relationships investigated can have predictable consequences on species leaf turnover strategies.

Authentication of Italian PDO lard using NIR spectroscopy, volatile profile and fatty acid composition combined with chemometrics.

This study analysed the usefulness of near infrared spectroscopy (NIRS), combined with volatile compound (VOC) and fatty acid (FA) analyses, for the authentication of the unique Italian Valle d'Aosta Arnad Protected Designation of Origin (PDO) lard. Ensuring the authenticity of high value meat products remains an emerging topic within the food sector. This study validated a FA, VOC and NIRS model for use in the authentication of Arnad PDO lard. The model showed a high potential rate to recognize patterns in lard samples. In particular the sensitivity and specificity calibration values were both 100%, and cross-validation models were performed using FAs and VOCs separately. The NIRS model obtained sensitivity and specificity values of 98.2% in the calibration data set, and 94.4% in the cross-validation step. This analytical approach may represent an effective tool to prevent food fraud, which is crucial for meat derived products with a high commercial value.

Differences in male coloration are predicted by divergent sexual selection between populations of a cichlid fish.

Female mating preferences can influence both intraspecific sexual selection and interspecific reproductive isolation, and have therefore been proposed to play a central role in speciation. Here, we investigate experimentally in the African cichlid fish Pundamilia nyererei if differences in male coloration between three para-allopatric populations (i.e. island populations with gene flow) of P. nyererei are predicted by differences in sexual selection by female mate choice between populations. Second, we investigate if female mating preferences are based on the same components of male coloration and go in the same direction when females choose among males of their own population, their own and other conspecific populations and a closely related para-allopatric sister-species, P. igneopinnis Mate-choice experiments revealed that females of the three populations mated species-assortatively, that populations varied in their extent of population-assortative mating and that females chose among males of their own population based on different male colours. Females of different populations exerted directional intrapopulation sexual selection on different male colours, and these differences corresponded in two of the populations to the observed differences in male coloration between the populations. Our results suggest that differences in male coloration between populations of P. nyererei can be explained by divergent sexual selection and that population-assortative mating may directly result from intrapopulation sexual selection.

Effect of management (organic vs conventional) on volatile profiles of six plum cultivars (Prunus salicina Lindl.). A chemometric approach for varietal classification and determination of potential markers.

The volatile profiles of six plum cultivars ('Laetitia', 'Primetime', 'Sapphire', 'Showtime', 'Songold' and 'Souvenir') produced under two management systems (conventional and organic) and harvested in two consecutive years were obtained by HS-SPME-GC-MS. Twenty-five metabolites were determined, five of which (pentanal, (E)-2-heptenal, 1-octanol, eucalyptol and 2-pentylfuran) are reported for the first time in Prunus salicina Lindl. Hexanal stood out as a major volatile compound affected by the management system. In addition, partial least square discriminant analysis (PLS-DA) achieved an effective classification of genotypes based on their volatile profiles. A high classification accuracy model was obtained with a sensitivity of 97.9% and a specificity of 99.6%. Furthermore, the application of a dual criterion, based on a method of variable selection, VIP (variable importance in projection) and the results of a univariate analysis (ANOVA), allowed the identification of potential volatile markers in 'Primetime', 'Showtime' and 'Souvenir' genotypes (cultivars not characterised to date).

Effect of hydroxytyrosol on quality of sulfur dioxide-free red wine.

In this work, the feasibility of two commercial products enriched in hydroxytyrosol (HT) as alternative to sulfur dioxide in Syrah red wines was evaluated. The HT enriched products came from synthesis and from olive waste. Wines treated with HT were compared with wines treated with sulfur dioxide at two winemaking stages: bottling and after 6 months of storage in bottle. Minor differences were found in enological parameters and volatile composition (esters, alcohols and acids). Significant differences were observed in color related parameters and sensory analysis. HT wines improved color parameters as well as scents and tasting at bottling. However, after 6 months of storage in bottle HT wines were more oxidized than SO2 wines. The olfactometry profile of HT wines supported sensory analysis. HT wines showed new odorant zones from both the added product and oxidation.

SPROUTY-2 represses the epithelial phenotype of colon carcinoma cells via upregulation of ZEB1 mediated by ETS1 and miR-200/miR-150.

SPROUTY-2 (SPRY2) is a modulator of tyrosine kinase receptor signaling with receptor- and cell type-dependent inhibitory or enhancing effects. Studies on the action of SPRY2 in major cancers are conflicting and its role remains unclear. Here we have dissected SPRY2 action in human colon cancer. Global transcriptomic analyses show that SPRY2 downregulates genes encoding tight junction proteins such as claudin-7 and occludin and other cell-to-cell and cell-to-matrix adhesion molecules in human SW480-ADH colon carcinoma cells. Moreover, SPRY2 represses LLGL2/HUGL2, PATJ1/INADL and ST14, main regulators of the polarized epithelial phenotype, and ESRP1, an epithelial-to-mesenchymal transition (EMT) inhibitor. A key action of SPRY2 is the upregulation of the major EMT inducer ZEB1, as these effects are reversed by ZEB1 knock-down by means of RNA interference. Consistently, we found an inverse correlation between the expression level of claudin-7 and those of SPRY2 and ZEB1 in human colon tumors. Mechanistically, ZEB1 upregulation by SPRY2 results from the combined induction of ETS1 transcription factor and the repression of microRNAs (miR-200 family, miR-150) that target ZEB1 RNA. Moreover, SPRY2 increased AKT activation by epidermal growth factor, whereas AKT and also Src inhibition reduced the induction of ZEB1. Altogether, these data suggest that AKT and Src are implicated in SPRY2 action. Collectively, these results show a tumorigenic role of SPRY2 in colon cancer that is based on the dysregulation of tight junction and epithelial polarity master genes via upregulation of ZEB1. The dissection of the mechanism of action of SPRY2 in colon cancer cells is important to understand the upregulation of this gene in a subset of patients with this neoplasia that have poor prognosis.

Control of hepatic glucose metabolism by islet and brain.

Dysregulation of hepatic glucose uptake (HGU) and inability of insulin to suppress hepatic glucose production (HGP) contribute to hyperglycaemia in patients with type 2 diabetes (T2D). Growing evidence suggests that insulin can inhibit HGP not only through a direct effect on the liver but also through a mechanism involving the brain. Yet, the notion that insulin action in the brain plays a physiological role in the control of HGP continues to be controversial. Although studies in dogs suggest that the direct hepatic effect of insulin is sufficient to explain day-to-day control of HGP, a surprising outcome has been revealed by recent studies in mice, investigating whether the direct hepatic action of insulin is necessary for normal HGP: when the hepatic insulin signalling pathway was genetically disrupted, HGP was maintained normally even in the absence of direct input from insulin. Here, we present evidence that points to a potentially important role of the brain in the physiological control of both HGU and HGP in response to input from insulin as well as other hormones and nutrients.

The influence of environmental factors on the abundance and recruitment of the sand crab Emerita analoga (Stimpson 1857): source-sink dynamics?

The sandcrab Emerita analoga is the dominant species inhabiting sandy beaches along the Pacific coast of the American continent. In our study, 10 sandy beaches were sampled seasonally from 2006 to 2011, including coastal planktonic sampling from 2006 to 2008. Two major population cores were detected, the first one in the northern part of the study area and the second in the area immediately to the south of the Itata River mouth. Zoeal stages were found along the entire coastal zone. Highest densities and recruitment were found during spring and summer of each year. PLS regression indicated that source-sink habitat proxies correlated positively with morphodynamic parameters; while beach slope and total organic matter were negatively correlated. These results agree with the source-sink hypothesis, finding higher densities of adults, recruits and cohort recurrence on open coast beaches with milder physical dynamics. Furthermore, a hypoxic event and a mega-earthquake/tsunami negatively affected recruitment at the inter-annual scale.

Insulin detemir attenuates food intake, body weight gain and fat mass gain in diet-induced obese Sprague-Dawley rats.

OBJECTIVE: Initiation and intensification of insulin therapy commonly causes weight gain, a barrier to therapy. A contrasting body of evidence indicates that insulin functions as an adiposity negative feedback signal and reduces food intake, weight gain and adiposity via action in the central nervous system. Basal insulin analogs, detemir (Det) and glargine (Glar), have been associated with less hypoglycemia compared with neutral protamine hagedorn insulin, and Det with less weight gain, especially in patients with higher body mass index (BMI). We sought to determine whether insulin therapy per se causes body weight and fat mass gain when delivered via a clinically relevant subcutaneous (SC) route in the absence of hypoglycemia and glycosuria in non-diabetic lean and diet-induced obese rats. MATERIALS AND METHODS: Rats were exposed to either a low-fat diet (LFD; 13.5% fat) or high-fat diet (HFD; 60% fat), and received Det (0.5 U kg(-1)), Glar (0.2 U kg(-1)) or vehicle (Veh) SC once daily for 4 weeks. These dosages of insulin were equipotent in rats with respect to blood-glucose concentration and did not induce hypoglycemia. RESULTS: As predicted by current models of energy homeostasis, neither insulin Det nor Glar therapy affected food intake and weight gain in LFD rats. Det treatment significantly attenuated food intake, body weight gain and fat mass gain relative to the Glar and Veh in high-fat fed animals, mirroring observations in humans. CONCLUSIONS: That neither insulin group gained excess weight, suggests weight gain with SC basal insulin therapy may not be inevitable. Our data further suggest that Det possesses a unique property to attenuate the development of obesity associated with a HFD.

SPROUTY-2 and E-cadherin regulate reciprocally and dictate colon cancer cell tumourigenicity.

SPROUTY-2 (SPRY2) regulates receptor tyrosine kinase signalling and therefore cell growth and differentiation. In this study, we show that SPRY2 expression in colon cancer cells is inhibited by the active vitamin D metabolite 1alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) through E-cadherin-dependent and -independent mechanisms. In turn, SPRY2 represses both basal and 1,25(OH)(2)D(3)-induced E-cadherin expression. In line with this, SPRY2 induces ZEB1 RNA and protein, but not that of other epithelial-to-mesenchymal transition inducers that repress the CDH1/E-cadherin promoter. Consistently, SPRY2 and E-cadherin protein levels inversely correlate in colon cancer cell lines and xenografted tumours. Moreover, SPRY2 knockdown by small hairpin RNA increases CDH1/E-cadherin expression and, reciprocally, CDH1/E-cadherin knockdown increases that of SPRY2. In colon cancer patients, SPRY2 is upregulated in undifferentiated high-grade tumours and at the invasive front of low-grade carcinomas. Quantification of protein expression in 34 tumours confirmed an inverse correlation between SPRY2 and E-cadherin. Our data demonstrate a tumourigenic action of SPRY2 that is based on the repression of E-cadherin, probably by the induction of ZEB1, and a reciprocal regulation of SPRY2 and E-cadherin that dictates cell phenotype. We propose SPRY2 as a candidate novel marker for high-grade tumours and a target of therapeutic intervention in colon cancer.

Stable isotope ratio analysis as a tool to discriminate between rainbow trout (O. mykiss) fed diets based on plant or fish-meal proteins.

The use of stable isotope ratio analysis (SIRA) as a rapid analytical tool to characterize and discriminate farmed fish on the basis of the feedstuffs included in the diet formulation is discussed. Two isoproteic (44.8%) and isolipidic (19.6%) extruded diets were formulated: a fish-meal-based diet (FM diet), containing fish meal as the sole protein source; a plant-protein-based diet (PP diet), where pea protein concentrate and wheat gluten meal replaced 80% of fish meal protein. The diets were fed to eight groups of rainbow trout (initial body weight: 106.6g) for 103 days in two daily meals under controlled rearing conditions. Growth performance (final body weight: 318.5 g; specific growth rate: 1.06%) and feed-to-gain ratio (0.79) were not affected by the dietary treatment. The differences in isotopic values of the two diets were clearly reflected in the different carbon and nitrogen isotopic values in rainbow trout fillets. The delta(13)C and delta(15)N values of muscle of farmed rainbow trout showed differences between farmed fish fed a fish-protein-based diet (-20.47 +/- 0.34 and 12.38 +/- 0.57 for delta(13)C and delta(15)N, respectively) and those fed a plant-protein-based diet (-23.96 +/- 0.38 and 7.15 +/- 0.51 for delta(13)C and delta(15)N, respectively). The results suggest that SIRA provides a robust and verifiable analytical tool to discriminate between fish fed on a plant or a fish protein diet.

Epigenetic inactivation of the ERK inhibitor Spry2 in B-cell diffuse lymphomas.

Spry2 has been characterized as a negative regulator of the extracellular-regulated kinase (ERK) pathway. In this study we analysed whether epigenetic alterations of hSpry2 promoter occur in human lymphoid/hematopoietic malignancies. Our results revealed that hSpry2 promoter was hypermethylated in the HT cell line derived from a B-cell diffuse lymphoma, which correlated with decreased hSpry2 expression. We detected deregulation of the ERK pathway in these cells, but not in other blood cell lines expressing hSpry2. In addition, the ectopic overexpression of hSpry2 in HT cells drastically reduced the activation of ERK upon phorbol 12-myristate-13-acetate stimulation. Nude mice inoculated with HT mock cells developed tumors seven times larger than those from HT-hSpry2-transfected cells. We found hypermethylation of hSpry2 promoter in 37% (26 cases out of 71) of primary tumors from patients with B-cell diffuse lymphoma but none in normal B lymphocytes from 37 healthy individuals. Finally, we detected that hSpry2 promoter hypermethylation was associated with a significant decrease in the 5-year survival rate. These data suggest that hSpry2 could be important in lymphoid malignancies.

Clinical evaluation of BCR-ABL peptide immunisation in chronic myeloid leukaemia: results of the EPIC study.

Peptides from the e14a2 BCR-ABL junction will elicit T-cell responses in vitro. Here, 19 imatinib treated CML patients in first chronic phase were vaccinated with BCR-ABL peptides spanning the e14a2 fusion junction, some of which were linked to the pan DR epitope PADRE to augment CD4+ T cell help. Six vaccinations were given over 9 weeks, together with sargramostim. All patients developed mild local reactions. T cell responses to PADRE were seen in all patients. Fourteen of 19 patients developed T cell responses to BCR-ABL peptides. The development of an anti-BCR-ABL T cell response correlated with a subsequent fall in BCR-ABL transcripts. No molecular benefit was seen in the 5 patients not in major cytogenetic response (MCR) at baseline. However, of the 14 patients in MCR at baseline, 13 developed at least 1 log fall in BCR-ABL transcripts, though this occurred several months after completing vaccination, consistent with an effect at a primitive CML stem cell level. Vaccination may improve the fall in BCR-ABL transcripts in patients who have received imatinib for more than 12 months. BCR-ABL peptide vaccination may improve control of CML, especially in patients responding well to imatinib. Randomised trials are required to address this further.

Inter-laboratory comparison of elemental analysis and gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS). Part I: delta13C measurements of selected compounds for the development of an isotopic Grob-test.

This study was directed towards investigating suitable compounds to be used as stable isotope reference materials for gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) calibration. Several compounds were selected from those used in the 'Grob-test' mixture. Oxygen- and nitrogen-containing substances were added to these compounds to allow the mixture to be used as a possible multi-isotopic calibration tool for 2H/1H, 13C/12C, 15N/14N and 18O/16O ratio determinations. In this paper we present the results of delta13C measurements performed by the consortium of the five laboratories taking part in this inter-calibration exercise. All the compounds were individually assessed for homogeneity, short-term stability and long-term stability by means of EA-IRMS, as required by the bureau communitaire de reference (BCR) Guide for Production of Certified Reference Materials. The results were compared then with the GC-C-IRMS measurements using both polar and non-polar columns, and the final mixture of selected compounds underwent a further certification exercise assessing limits of accuracy and reproducibility under specified GC-C-IRMS conditions.

Aplidin induces JNK-dependent apoptosis in human breast cancer cells via alteration of glutathione homeostasis, Rac1 GTPase activation, and MKP-1 phosphatase downregulation.

Aplidin is an antitumor agent in phase II clinical trials that induces apoptosis through the sustained activation of Jun N-terminal kinase (JNK). We report that Aplidin alters glutathione homeostasis increasing the ratio of oxidized to reduced forms (GSSG/GSH). Aplidin generates reactive oxygen species and disrupts the mitochondrial membrane potential. Exogenous GSH inhibits these effects and also JNK activation and cell death. We found two mechanisms by which Aplidin activates JNK: rapid activation of Rac1 small GTPase and downregulation of MKP-1 phosphatase. Rac1 activation was diminished by GSH and enhanced by L-buthionine (SR)-sulfoximine, which inhibits GSH synthesis. Downregulation of Rac1 by transfection of small interfering RNA (siRNA) duplexes or the use of a specific Rac1 inhibitor decreased Aplidin-induced JNK activation and cytotoxicity. Our results show that Aplidin induces apoptosis by increasing the GSSG/GSH ratio, a necessary step for induction of oxidative stress and sustained JNK activation through Rac1 activation and MKP-1 downregulation.

The isoform-specific stretch of hSos1 defines a new Grb2-binding domain.

hSos1 isoform II, defined by the presence of a 15 amino acid stretch in its carboxy-terminal region, exhibits higher Grb2 affinity than hSos1 isoform I. In this study, we investigated the cause for this difference and observed that, in addition to the four currently accepted Grb2-binding motifs, a number of additional, putative SH3-minimal binding sites (SH3-MBS) could be identified. The isoform II-specific 15 amino acid stretch contained one of them. Indeed, we demonstrated by site-directed mutagenesis that these SH3-MBS were responsible for the Grb2 interaction, and we found that C-terminal fragments of the two hSos1 isoforms (lacking the four cannonical Grb2-binding motifs, but containing the SH3-minimal binding sites) were able to bind Grb2, with the isoform II fragment showing higher Grb2 affinity than the corresponding isoform I fragment. Furthermore, we provide evidence that C-terminal truncated mutants of either hSos1 isoform, containing only the SH3-minimal binding sites, were able to originate in vivo stable complexes with Grb2. Although, Grb2-binding remains higher in both full-length isoforms, compared to the C-terminal truncated mutants, these mutants were also able to activate Ras, supporting a potential role of this C-terminal region as negative modulator of Sos1 activity. These findings document the existence of a new, functional, SH3-minimal binding site located in the specific stretch of hSos1 isoform II which may be responsible for the increased Grb2 affinity of this isoform in comparison to isoform I, and for the physiological properties differences between both isoforms. Moreover, these SH3-minimal binding sites may be sufficient to attain stable and functional hSosl-Grb2 complexes.

Tumor cells present MHC class II-restricted nuclear and mitochondrial antigens and are the predominant antigen presenting cells in vivo.

MHC class II-restricted tumor Ags presented by class II(+) tumor cells identified to date are derived from proteins expressed in the cytoplasm or plasma membrane of tumor cells. It is unclear whether MHC class II(+) tumor cells present class II-restricted epitopes derived from other intracellular compartments, such as nuclei and/or mitochondria, and whether class II(+) tumor cells directly present Ag in vivo. To address these questions, a model Ag, hen egg lysozyme, was targeted to various subcellular compartments of mouse sarcoma cells, and the resulting cells were tested for presentation of three lysozyme epitopes in vitro and for presentation of nuclear Ag in vivo. In in vitro studies, Ags localized to all tested compartments (nuclei, cytoplasm, mitochondria, and endoplasmic reticulum) are presented in the absence invariant chain and H-2M. Coexpression of invariant chain and H-2M inhibit presentation of some, but not all, of the epitopes. In vivo studies demonstrate that class II(+) tumor cells, and not host-derived cells, are the predominant APC for class II-restricted nuclear Ags. Because class II(+) tumor cells are effective APC in vivo and probably present novel tumor Ag epitopes not presented by host-derived APC, their inclusion in cancer vaccines may enhance activation of tumor-reactive CD4(+) T cells.

A role for the p38 mitogen-acitvated protein kinase pathway in the transcriptional activation of p53 on genotoxic stress by chemotherapeutic agents.

The tumor suppressor p53 plays a central role in sensing damaged DNA and orchestrating the consequent cellular responses. However, how DNA damage leads to the activation of p53 is still poorly understood. In this study, we have found that the p38 mitogen-activated protein kinase (MAPK) plays a key role in the activation of p53 by genotoxic stress when provoked by chemotherapeutic agents. Indeed, we found that blockade of p38 prevents stimulation of the transcriptional activity of p53 and that activation of the p38 pathway is sufficient to stimulate p53 function. Furthermore, we observed that p38 does not affect the accumulation of p53 in response to DNA damage or its nuclear localization. In contrast, we observed that p38 associates physically with p53, and we provide evidence that this MAPK phosphorylates the NH2-terminal transactivation domain of p53 in serine 33, thereby stimulating its functional activity. Moreover, inhibition of the p38 MAPK diminished the apoptotic fraction of cells exposed to chemotherapeutic agents and increased cell survival, thus suggesting a role for p38 activation in the apoptotic response to genotoxic stress when elicited by drugs used in cancer therapy.