Maria Gabriella Torcia | Università degli Studi di Firenze (University of Florence) (original) (raw)

Papers by Maria Gabriella Torcia

ST258-K. pneumoniae (ST258-KP) strains, the most widespread multidrug-resistant hospital acquired... more ST258-K. pneumoniae (ST258-KP) strains, the most widespread multidrug-resistant hospital acquired pathogens, belong to at least two clades differing in a 215 Kb genomic region that includes the cluster of capsule genes. To investigate the effects of the different capsular phenotype on host-pathogen interactions, we studied representatives of ST258-KP clades, KKBO-1 and KK207-1, for their ability to activate monocytes and myeloid dendritic cells from human immune competent hosts. The two ST258-KP strains strongly induced the production of inflammatory cytokines. Significant differences between the strains were found in their ability to induce the production of IL-1β: KK207-1/clade I was much less effective than KKBO-1/clade II in inducing IL-1β production by monocytes and dendritic cells. The activation of NLRP3 inflammasome pathway by live cells and/or purified capsular polysaccharides was studied in monocytes and dendritic cells. We found that glibenclamide, a NLRP3 inhibi-tor, inhibits more than 90% of the production of mature IL-1β induced by KKBO1 and KK207-1. KK207-1 was always less efficient compared to KKBO-1 in: a) inducing NLRP3 and pro-IL-1β gene and protein expression; b) in inducing caspase-1 activation and pro-IL-1β cleavage. Capsular composition may play a role in the differential inflammatory response induced by the ST258-KP strains since capsular polysaccharides purified from bacterial cells affect NLRP3 and pro-IL-1β gene expression through p38MAPK-and NF-κB-mediated pathways. In each of these functions, capsular polysaccharides from KK207-1 were significantly less efficient compared to those purified from KKBO-1. On the whole, our data suggest that the change in capsular phenotype may help bacterial cells of clade I to partially escape innate immune recognition and IL-1β-mediated inflammation.

Interference with transforming growth factor-b-mediated pathways helps several parasites to survi... more Interference with transforming growth factor-b-mediated pathways helps several parasites to survive for long periods in immunocompetent hosts. Macrophages and dendritic cells infected by Toxoplasma, Leishmania and Plasmodium spp. produce large amounts of transforming growth factor-b and induce the differentiation of antigen-specific T-regulatory cells. Mechanisms not mediated by antigen-presentation could also account for the expansion of T-regulatory cells in parasitic diseases and they also might be mediated through transforming growth factor-b-receptor activated pathways. We explored the properties of soluble extracts from Leishmania infantum promastigotes, Toxoplasma gondii tachyzoites, Trichinella spiralis muscle larvae to expand the pool of T-regulatory cells in a population of polyclonally activated T cells in the absence of accessory cells, and compared their effects to those induced by Plasmodium falciparum extracts. Similarly to P. falciparum, L. infantum extracts activate the latent soluble form of transforming growth factor-b and that bound to the membrane of activated T lymphocytes. The interaction of the active cytokine with transforming growth factor-b receptor induces Foxp3 expression by activated lymphocytes, favoring their conversion through the T-regulatory phenotype. Both Toxoplasma gondii and L. infantum extracts are able to induce transforming growth factor-b production by activated T cells in the absence of accessory cells.

Multiple sclerosis is characterized by tissue atrophy involving the brain and the spinal cord, wh... more Multiple sclerosis is characterized by tissue atrophy involving the brain and the spinal cord, where reactive inflammation contributes to the neurodegenerative processes. Recently, the presence of synapse alterations induced by the inflammatory responses was suggested by experimental and clinical observations, in experimental autoimmune encephalomyelitis mouse model and in patients, respectively. Further knowledge on the interplay between pro-inflammatory agents, neuroglia and synaptic dysfunction is crucial to the design of unconventional protective molecules. Here we report the effects, on spinal cord circuits, of a cytokine cocktail that partly mimics the signature of T lymphocytes sub population Th1. In embryonic mouse spinal organ-cultures, containing neuronal cells and neuroglia, cytokines induced inflammatory responses accompanied by a significant increase in spontaneous synaptic activity. We suggest that cytokines specifically altered signal integration in spinal networks by speeding the decay of GABA A responses. This hypothesis is supported by the finding that synapse protection by a non-peptidic NGF mimetic molecule prevented both the changes in the time course of GABA events and in network activity that were left unchanged by the cytokine production from astrocytes and microglia present in the cultured tissue. In conclusion, we developed an important tool for the study of synaptic alterations induced by inflammation, that takes into account the role of neuronal and not neuronal resident cells.

Changes in cervico-vaginal microbiota with Lactobacillus depletion and increased microbial divers... more Changes in cervico-vaginal microbiota with Lactobacillus depletion and increased microbial diversity facilitate human papillomavirus (HPV) infection and might be involved in viral persistence and cancer development. To define the microbial Community State Types (CSTs) associated with high-risk HPV− persistence, we analysed 55 cervico-vaginal samples from HPV positive (HPV+) women out of 1029 screened women and performed pyrosequencing of 16S rDNA. A total of 17 samples from age-matched HPV negative (HPV−) women were used as control. Clearance or Persistence groups were defined by recalling women after one year for HPV screening and genotyping. A CST IV subgroup, with bacterial genera such as Gardnerella, Prevotella, Megasphoera, Atopobium, frequently associated with anaerobic consortium in bacterial vaginosis (BV), was present at baseline sampling in 43% of women in Persistence group, and only in 7.4% of women in Clearance group. Atopobium genus was significantly enriched in Persistence group compared to the other groups. Sialidase-encoding gene from Gardnerella vaginalis, involved in biofilm formation, was significantly more represented in Persistence group compared to the other groups. Based on these data, we consider the CST IV-BV as a risk factor for HPV persistence and we propose Atopobium spp and sialidase gene from G. vaginalis as microbial markers of HPV− persistence. Cervical cancer (CC) is one of the most common cancer in women, with an estimated incidence of 485 000 new cases and 236 000 deaths in 2013 1 , causing 6.9 million disability-adjusted life-years (DALYs). Persistence of onco-genic human papillomavirus (HPV) infection contribute to the development of CC. While the virus is cleared in more than 90% of infections within 6–18 months 2–4 , viral persistence occurs in almost 10% of infected women. The factors responsible of persistence, as well those that promote and initiate the carcinogenesis process, need to be fully elucidated. Many other factors such as immunodeficiency, age, smoking, oral contraceptives and Chlamydia trachomatis infection are related with higher persistence rates 5, 6. Recently, several scientific reports indicated the role of vaginal microbiota in the acquisition and persistence of HPV and risk of CC development 7. In the majority of human body sites, highly diverse microbial communities are generally considered a signature of health 8, 9. However, in the vaginal environment, health is commonly associated with low microbial diversity and prevalence of only a few species of Lactobacillus 10–13. Lactobacillus spp. prevent colonization of exogenous pathogens by producing lactic acid, bacteriocins and reactive oxygen species (ROS), and compete with them for Published: xx xx xxxx OPEN

The spread of KPC-type carbapenemases is mainly attributed to the global dissemination of Klebsie... more The spread of KPC-type carbapenemases is mainly attributed to the global dissemination of Klebsiella pneumoniae (KP) strains belonging to the clonal group (CG) 258, including sequence type (ST) 258 and other related STs. Two distinct clades of CG258-KP have evolved, which differ mainly for the composition of their capsular polysaccharides, and recent studies indicate that clade 1 evolved from an ancestor of clade 2 by recombination of a genomic fragment carrying the capsular polysaccharide (cps) locus. In this paper, we investigated the ability of two ST258-KP strains, KKBO-1 and KK207-1, selected as representatives of ST258-KP clade 2 and clade 1, respectively, to activate an adaptive immune response using ex vivo-stimulation of PBMC from normal donors as an experimental model. Our data showed that KKBO-1 (clade 2) induces a Th17 response more efficiently than KK207-1 (clade 1): the percentage of CD4 + IL17 + cells and the production of IL-17A were significantly higher in cultures with KKBO-1 compared to cultures with KK207-1. While no differences in the rate of bacterial internalization or in the bacteria-induced expression of CD86 and HLA-DR by monocytes and myeloid dendritic cells were revealed, we found that the two strains significantly differ in inducing the production of cytokines involved in the adaptive immune response, as IL-1β, IL-23 and TNF-α, by antigen-presenting cells, with KKBO-1 being a more efficient inducer than KK207-1. The immune responses elicited by KK207-1 were comparable to those elicited by CIP 52.145, a highly virulent K. pneumoniae reference strain known to escape immune-inflammatory responses. Altogether, present results suggest that CG258-KP of the two clades are capable of inducing a different response of adaptive immunity in the human host.

Crohn's disease (CD) is a multifactorial immunologically mediated disease. In this study we explo... more Crohn's disease (CD) is a multifactorial immunologically mediated disease. In this study we explored, for the first time, the efficacy of the Multiplex Gene Assay technology for detecting mRNA expression profile of 24 selected CD related genes in endoscopic biopsies and surgical specimens from CD patients with colonic localization of the disease. The polymorphisms of genes most frequently associated with CD were also analysed in DNA samples from the same patients. The analysis of endoscopic samples showed increased expression of 7 genes in inflamed mucosa compared to non-inflamed mucosa and suggests the activation of the autophagy process and of a Th17 adaptive response. The analysis of surgical specimens showed increased expression of 16 genes in inflamed tissue compared to non-inflamed internal controls and revealed the activation of immune-adaptive Th17 response in association with a Th1 response.

Candida spp. usually colonize ulcerative lesions of atrophic mucosa in patients with chemotherapy... more Candida spp. usually colonize ulcerative lesions of atrophic mucosa in patients with chemotherapy-induced oral mucositis inducing severe inflammation. The spread of antifungal-esistant strains strongly encouraged the search of complementary or alternative therapeutic strategies to cure inflamed mucosa. In this paper, we studied the effects of a near-infrared (NIR) laser system with dual-wavelength emission (808 nm+904 nm) on the survival and inflammatory potential of C. albicans, C. glabrata, and C. parapsilosis. Laser treatment was performed with a Multiwave Locked System laser. Survival and apoptosis of fungal strains were evaluated by colony-forming units (CFU) counting and annexin V staining. Cytokine production was evaluated by ImmunoPlex array. Laser treatment significantly affected the survival of Candida spp. by inducing apoptosis and induced a lower production of inflammatory cytokines by dendritic cells compared to untreated fungi. No differences in the survival and inflammatory potential were recorded in treated or untreated Saccharomyces cerevisiae cells, used as the control nonpathogenic microorganism. Laser treatment altered the survival and inflammatory potential of pathogenic Candida spp. These data provide experimental support to the use of NIR laser radiation as a co-adjuvant of antifungal therapy in patients with oral mucositis (OM) complicated by Candida infections.

Despite inflammatory and immune mechanisms participating to atherogenesis and dendritic cells (DC... more Despite inflammatory and immune mechanisms participating to atherogenesis and dendritic cells (DCs) driving immune and non-immune tissue injury response, the interactions between DCs and vascular smooth muscle cells (VSMCs) possibly relevant to vascular pathology including atherogenesis are still unclear. To address this issue, immature DCs (iDCs) generated from CD14 + cells isolated from healthy donors were matured either with cytokines (mDCs), or co-cultured (ccDCs) with human coronary artery VSMCs (CASMCs) using transwell chambers. Co-culture induced DC immunophenotypical and functional maturation similar to cytokines, as demonstrated by flow cytometry and mixed lymphocyte reaction. In turn, factors from mDCs and ccDCs induced CASMC migration. MCP-1 and TNFa, secreted from DCs, and IL-6 and MCP-1, secreted from CASMCs, were primarily involved. mDCs adhesion to CASMCs was enhanced by CASMC pre-treatment with IFNc and TNFa ICAM-1 and VCAM-1 were involved, since the expression of specific mRNAs for these molecules increased and adhesion was inhibited by neutralizing antibodies to the counter-receptors CD11c and CD18. Adhesion was also inhibited by CASMC pre-treatment with the HMG-CoA-reductase inhibitor atorvastatin and the PPARc agonist rosiglitazone, which suggests a further mechanism for the anti-inflammatory action of these drugs. Adhesion of DCs to VSMCs was shown also in vivo in rat carotid 7 to 21 days after crush and incision injury. The findings indicate that DCs and VSMCs can interact with reciprocal stimulation, possibly leading to perpetuate inflammation and vascular wall remodelling, and that the interaction is enhanced by a cytokine-rich inflammatory environment and down-regulated by HMGCoA-reductase inhibitors and PPARc agonists.

The optimal immune response to malaria infection comprises rapid induction of inflammatory respon... more The optimal immune response to malaria infection comprises rapid induction of inflammatory responses promptly counteracted by regulatory mechanisms to prevent immunopathology. To evaluate the role of dendritic cells (DC) in the balance of parasite induced inflammatory/anti-inflammatory mechanisms, we studied the activity of monocyte-derived dendritic cells (MDDC), previously exposed to soluble extracts of Plasmodium falciparum-infected red blood cells (PfSE), in the differentiation of CD4 cells isolated from donors never exposed to malaria infection. We show that MDDC exposed to PfSE are extremely efficient to induce a contemporary differentiation of TH1 effector cells and T regulatory (Treg) cells in CD4 T cells even when exposed to low concentrations of parasitic extracts. Treg cells induced by MDDC infected with PfSE (MDDC-PfSE) produce transforming growth factor beta (TGF-) and interleukin 10 (IL-10) and are endowed with strong suppressive properties. They also show phenotypical and functional peculiarities, such as the contemporary expression of markers of Treg and TH1 differentiation and higher sensitivity to TLR4 ligands both inducing an increasing production of suppressive cytokines. On the whole, our data indicate that MDDC exposed to PfSE orchestrate a well-balanced immune response with timely differentiation of TH1 and Treg cells in CD4 cells from nonimmune donors and suggest that, during the infection, the role of MDCC could be particularly relevant in low-parasitemia conditions.

Haematological parameters, natural regulatory CD4 + CD25 + FOXP3+ T cells and gδ T cells among tw... more Haematological parameters, natural regulatory CD4 + CD25 + FOXP3+ T cells and gδ T cells among two sympatric ethnic groups having different susceptibility to malaria in Burkina Faso Abstract Background: Fulani ethnic group individuals are less susceptible than sympatric Mossi ethnic group, in term of malaria infection severity, and differ in antibody production against malaria antigens. The differences in susceptibility to malaria between Fulani and Mossi ethnic groups are thought to be regulated by different genetic backgrounds and offer the opportunity to compare haematological parameters, Tregs and gδT cell profiles in seasonal and stable malaria transmission settings in Burkina Faso. The study was conducted at two different time points i.e. during the high and low malaria transmission period. Results: Two cross-sectional surveys were undertaken in adults above 20 years belonging either to the Fulani or the Mossi ethnic groups 1) at the peak of the malaria transmission season and 2) during the middle of the low malaria transmission season. Full blood counts, proportions of Tregs and gδ T cells were measured at both time-points. As previously shown the Fulani and Mossi ethnic groups showed a consistent difference in P. falciparum infection rates and parasite load. Differential white blood cell counts showed that the absolute lymphocyte counts were higher in the Mossi than in the Fulani ethnic group at both time points. While the proportion of CD4+CD25 high was higher in the Fulani ethnic group at the peak of malaria transmission season (p = 0.03), no clear pattern emerged for T regulatory cells expressing FoxP3 + and CD127 low. However CD3 + gδ + subpopulations were found to be higher in the Fulani compared to the Mossi ethnic group, and this difference was statistically significant at both time-points (p = 0.004 at low transmission season and p = 0.04 at peak of transmission). Conclusion: Our findings on regulatory T cell phenotypes suggest an interesting role for immune regulatory mechanisms in response to malaria. The study also suggests that TCRgδ + cells might contribute to the protection against malaria in the Fulani ethnic group involving their reported parasite inhibitory activities.

To elucidate mechanisms underlying neovascularization that accompanies certain chronic immune/ in... more To elucidate mechanisms underlying neovascularization that accompanies certain chronic immune/ inflammatory disorders, the effects of interferon-a (IFN-a) and interleukin 2 (IL-2) on endothelial cell (EC) growth in vitro and angiogenesis in vivo were studied. Preincubation of cultured human ECs with IFN-a, followed by exposure to IL-2, resulted in effective stimulation of cell growth, whereas either cytokine alone had only a slight effect. The combination of IFN-a/IL-2 induced an an-giogenic response in the rabbit cornea. IL-2 receptor expression was enhanced on IFN-a-treated ECs: p55 was increased and p70 was induced. '25I-IL-2 binding to ECs treated with IFN-a was enhanced (Kd from 7 nM to 260 pM with IFN-a), and anti-p55 IgG blocked '25I-IL-2/EC interaction as well as IL-2-mediated EC proliferation. Consistent with these findings in cell culture, immunohistologic studies demonstrated p55 and p70 antigen in the vasculature of rheumatoid joints, but not in normal joint tissue. Exposure of cultured ECs to IFN-a increased levels of intracellular EC basic fibroblast growth factor (bFGF), and subsequent addition of IL-2 led to bFGF release into the medium. The observation that anti-bFGF IgG largely blocked EC proliferation in response to IFN-a/IL-2 suggested that bFGF was a critical agent in this setting. These data suggest a mechanism rendering ECs responsive to IL-2 which may be relevant in immune/inflammatory disorders: IFN-a-mediated induction of functional EC receptors for IL-2, which drives cell proliferation by a mechanism dependent on increased synthesis and release of bFGF. (J. Clin. Invest. 1993. 91:2504-2512.)

Background: Susceptibility to viral infections as well as their severity are higher in men than i... more Background: Susceptibility to viral infections as well as their severity are higher in men than in women. Heightened antiviral responses typical of women are effective for rapid virus clearance, but if excessively high or prolonged, can result in chronic/ inflammatory pathologies. We investigated whether this variability could be in part attributable to differences in the response to the Toll-Like Receptors (TLR) more involved in the virus recognition.

Exploitation of the biologic activity of neurotrophins is desirable for medical purposes, but the... more Exploitation of the biologic activity of neurotrophins is desirable for medical purposes, but their protein nature intrinsically bears adverse pharmacokinetic properties. Here, we report synthesis and biologic characterization of a novel class of low molecular weight, non-peptidic compounds with NGF (nerve growth factor)-mimetic properties. MT2, a representative compound, bound to Trk (tropomyosin kinase receptor)A chain on NGF-sensitive cells, as well as in cell-free assays, at nanomolar concentrations and induced TrkA autophosphorylation and receptor-mediated internalization. MT2 binding involved at least two amino-acid residues within TrkA molecule. Like NGF, MT2 increased phosphorylation of extracellular signal-regulated kinase1/2 and Akt proteins and production of MKP-1 phosphatase (dual specificity phosphatase 1), modulated p38 mitogen-activated protein kinase activation, sustained survival of serum-starved PC12 or RDG cells, and promoted their differentiation. However, the intensity of such responses was heterogenous, as the ability of maintaining survival was equally possessed by NGF and MT2, whereas the induction of differentiation was expressed at definitely lower levels by the mimetic. Analysis of TrkA autophosphorylation patterns induced by MT2 revealed a strong tyrosine (Tyr)490 and a limited Tyr785 and Tyr674/675 activation, findings coherent with the observed functional divarication. Consistently, in an NGF-deprived rat hippocampal neuronal model of Alzheimer Disease, MT2 could correct the biochemical abnormalities and sustain cell survival. Thus, NGF mimetics may reveal interesting investigational tools in neurobiology, as well as promising drug candidates.

Increased numbers of T regulatory cells (Tregs), key mediators of immune homeostasis, were report... more Increased numbers of T regulatory cells (Tregs), key mediators of immune homeostasis, were reported in human and murine malaria and it is current opinion that these cells play a role in balancing protective immunity and pathogenesis during infection. However, the mechanisms governing their expansion during malaria infection are not completely defined. In this article we show that soluble extracts of Plasmodium falciparum (PfSEs), but not equivalent preparation of uninfected eryth-rocytes, induce the differentiation of polyclonally activated CD4 + cells in Tregs endowed with strong suppressive activity. PfSEs activate latent TGFb bound on the membrane of Treg cells, thus allowing the cytokine interaction with TGFb receptor, and inducing Foxp3 gene expression and TGFb production. The activation of membrane-bound latent TGFb by PfSEs is significantly reduced by a broad-spectrum metalloproteinases inhibitor with Zn ++-chelating activity, and completely inhibited by the combined action of such inhibitor and antibodies to a P. falciparum thrombospondin-related adhesive protein (PfTRAP). We conclude that Pf-Zn ++-dependent proteinases and, to a lesser extent, PfTRAP molecules are involved in the activation of latent TGFb bound on the membrane of activated Treg cells and suggest that, in malaria infection, this mechanism could contribute to the expansion of Tregs with different antigen specificity.

Wound repair and tumor vascularization depend upon blood vessel growth into hypoxic tissue. Altho... more Wound repair and tumor vascularization depend upon blood vessel growth into hypoxic tissue. Although hypoxia slows endothelial cell (EC) proliferation and suppresses EC basic fibroblast growth factor (bFGF) expression , we report that macrophages (MPs) exposed to Po2 12-14 torr (1 torr = 1333 Pa) synthesize and release in a time-dependent manner platelet-derived growth factor (PDGF) and acidic/basic FGFs (a/bFGFs), which stimulate the growth of hypoxic ECs. Chromatography of hypoxic MP-conditioned medium on immobilized heparin with an ascending NaCl gradient resolved three peaks of mitogenic activity: activity of the first peak was neutralized by antibody to PDGF; activity of the second peak was neutralized by antibody to aFGF; and activity of the third peak was neutralized by antibody to bFGF. Metabolically labeled lysates and supernatants from MPs exposed to hypoxia showed increased synthesis and release of immunoprecipitable PDGF and a/bFGF in the absence of changes in cell viability. Possible involvement of a heme-containing oxygen sensor in MP elaboration of growth factors was suggested by the induction of bFGF and PDGF by normoxic MPs exposed to nickel or cobalt, although metabolic inhibitors such as sodium azide were without effect. These results suggest a paracrine model in which hypoxia stimulates MP release of PDGF and a/bFGF, inducing EC proliferation and potentially promoting angiogenesis in hypoxic environments.

The molecular mechanisms underlying the growth inhibition induced by interferon-(IFN-) in B16 mu-... more The molecular mechanisms underlying the growth inhibition induced by interferon-(IFN-) in B16 mu-rine melanoma cells were investigated. IFN-did not induce cell apoptosis, but strongly interfered with the synthesis of basic fibroblast growth factor (bFGF), which acts as an autocrine growth factor in this system. Inhibition of bFGF synthesis was observed at the same concentrations (50 –500 pM, 10 –100 U/ml) of IFN-able to induce growth arrest of B16 melanoma cells. Although the synthesis of acidic (a)FGF was only slightly affected by IFN-, the cytokine induced release of an aFGF-related low-molecular-weight pep-tide, which was able to interfere with bFGF binding to surface receptors. Thus, the molecular mechanisms of IFN-activity on melanoma cells include a specific modulation of the bFGF autocrine circuit.

The sIgG lymphoblastoid B cell line CESS spontaneously produces a high amount of NGF and expresse... more The sIgG lymphoblastoid B cell line CESS spontaneously produces a high amount of NGF and expresses both high affinity (p140 Trk-A) and low affinity (p75 NTR) NGF receptors. Blocking NGF signals with neutralizing antibodies or specific Trk-A inhibitors induces a rapid phosphorylation of antiapoptotic Bcl-2 protein, followed by caspase activation, and apoptotic death of CESS cells. Bcl-2 phosphorylation in several sites within a 60 aa " loop " domain of protein is known to regulate its antiapoptotic function. Accordingly, CESS cells expressing the loop deletional mutant cDNA constructs Bcl-2 40-91 were completely resistant to apop-tosis induced by NGF withdrawal, indicating that Bcl-2 phosphorylation is a critical event. NGF withdrawal induces p38 MAPK, but not JNK, activation in CESS cells, and SB203580, a specific inhibitor of p38 MAPK, is able to prevent both Bcl-2 phosphorylation and apoptosis, indicating that p38 MAPK is the enzyme responsible for these events.

Survival of memory B lymphocytes is tightly linked to the integrity of the Bcl-2 protein and is r... more Survival of memory B lymphocytes is tightly linked to the integrity of the Bcl-2 protein and is regulated by a nerve growth factor (NGF) autocrine circuit. In factor-starved memory B cells, the addition of exogenous NGF promptly induced p38 mitogen-activated protein kinase (MAPK), but not c-Jun N-terminal kinase (JNK), dephos-phorylation. Conversely, withdrawal of endogenous NGF was followed by p38 MAPK activation and translo-cation onto mitochondria, whereby it combined with and phosphorylated Bcl-2, as assessed by co-immuno-precipitation and kinase assays in vivo and in vitro. Mitochondria isolated from human memory B cells, then exposed to recombinant p38 MAPK, released cyto-chrome c, as did mitochondria from Bcl-2-negative MDCK cells loaded with recombinant Bcl-2. Apoptosis induced by NGF neutralization could be blocked by the specific p38 MAPK inhibitor SB203580 or by Bcl-2 mutations in Ser-87 or Thr-56. These data demonstrate that the molecular mechanisms underlying the survival factor function of NGF critically rely upon the continuous inactivation of p38 MAPK, a Bcl-2-modifying enzyme.