Thymosin ß4 and ß10 are highly expressed at the deep infiltrative margins of colorectal cancer - A mass spectrometry analysis.

OBJECTIVE: Colorectal cancer (CRC) is a complicated tumor, involving several oncogenic signaling pathways, and with a molecular mechanism not fully understood yet. The implication of thymosin ß4 (Tß4) with tumor insurgence and in migration of CRC cells was evidenced in the past with different methodologies, while Tß10 connection with CRC has been sporadically investigated. This study focused on the implication of both types of thymosin in CRC progression and invasion by analyzing the changes in their levels according to different zones of the tumor, and to Dukes stage and budding index. PATIENTS AND METHODS: Tß4 and Tß10 were analyzed in deep and superficial tumor samples, and normal mucosa from 18 patients. Concentrations of Tß4 and Tß10 have been measured by high-pressure liquid chromatography (HPLC) coupled to electrospray-ion trap mass spectrometry (ESI-IT-MS). MS data were compared by t-test and ANOVA statistical analysis. Identification of thymosin and their proteoforms has been performed by HPLC-high resolution-ESI-IT-MSMS. RESULTS: Both Tß4 and Tß10, exhibited intra-tumoral quantitative differences, being upregulated in the deep part of the CRC. They exhibited, moreover, strong association with the Dukes stage and the budding grade, being more concentrated in patients at Dukes stage B and with budding index "2". CONCLUSIONS: The results obtained in the present investigation encouraged the hypothesis that the two thymosin are involved in colorectal cancer progression, and in promoting cancer invasion. Thus, they are good candidates to be diagnostic/prognostic biomarkers and therapy targets.

Salivary biomarkers and proteomics: future diagnostic and clinical utilities.

Saliva testing is a non-invasive and inexpensive test that can serve as a source of information useful for diagnosis of disease. As we enter the era of genomic technologies and -omic research, collection of saliva has increased. Recent proteomic platforms have analysed the human salivary proteome and characterised about 3000 differentially expressed proteins and peptides: in saliva, more than 90% of proteins in weight are derived from the secretion of three couples of "major" glands; all the other components are derived from minor glands, gingival crevicular fluid, mucosal exudates and oral microflora. The most common aim of proteomic analysis is to discriminate between physiological and pathological conditions. A proteomic protocol to analyze the whole saliva proteome is not currently available. It is possible distinguish two type of proteomic platforms: top-down proteomics investigates intact naturally-occurring structure of a protein under examination; bottom-up proteomics analyses peptide fragments after pre-digestion (typically with trypsin). Because of this heterogeneity, many different biomarkers may be proposed for the same pathology. The salivary proteome has been characterised in several diseases: oral squamous cell carcinoma and oral leukoplakia, chronic graft-versus-host disease Sjögren's syndrome and other autoimmune disorders such as SAPHO, schizophrenia and bipolar disorder, and genetic diseases like Down's Syndrome and Wilson disease. The results of research reported herein suggest that in the near future human saliva will be a relevant diagnostic fluid for clinical diagnosis and prognosis.

Proteomic characterization of the qualitative and quantitative differences in cervical mucus composition during the menstrual cycle.

The chemical composition of the cervical mucus (CM), its physical characteristics and the volume of secretion change cyclically throughout the menstrual cycle. The aim of this study was to identify the constitutive protein composition of CM of fertile women and the changes in the CM proteome throughout the menstrual cycle. Five fertile women who had a term delivery within 1 year before the study were enrolled. Proteomic analysis was performed using an Ultimate 3000 Nano/Micro-HPLC apparatus equipped with an FLM-3000-Flow manager module and coupled with an LTQ Orbitrap XL hybrid mass spectrometer; bioinformatic software was used for functional and quantitative analysis. 59, 81 and 43 proteins (mean) were respectively identified in the pre-ovulatory, ovulatory and post-ovulatory samples. 38 common proteins were identified. 42, 38 and 17 exclusive proteins were respectively identified in pre-ovulatory, ovulatory and post-ovulatory CM. The main part of CM constituents has a catalytic activity, which is mainly related to hydrolase activity. The label-free quantitative analysis of the common proteins revealed a significant reduction in the protein abundance index for antileukoproteinase, after the ovulation, and a peak of haptoglobin at ovulation. This is the first application of high-resolution MS-based proteomics for the identification of protein constituents of CM. This approach may contribute to the identification of putative biomarkers of the female reproductive tract.

Thymosin beta 4 and thymosin beta 10 expression in hepatocellular carcinoma.

Thymosin beta 4 (Tß4) and thymosin beta 10 (Tß10) are two members of the beta-thymosin family involved in many cellular processes such as cellular motility, angiogenesis, inflammation, cell survival and wound healing. Recently, a role for beta-thymosins has been proposed in the process of carcinogenesis as both peptides were detected in several types of cancer. The aim of the present study was to investigate the expression pattern of Tß4 and Tß10 in hepatocellular carcinoma (HCC). To this end, the expression pattern of both peptides was analyzed in liver samples obtained from 23 subjects diagnosed with HCC. Routinely formalin-fixed and paraffin-embedded liver samples were immunostained by indirect immunohistochemistry with polyclonal antibodies to Tß4 and Tß10. Immunoreactivity for Tß4 and Tß10 was detected in the liver parenchyma of the surrounding tumor area. Both peptides showed an increase in granular reactivity from the periportal to the periterminal hepatocytes. Regarding HCC, Tß4 reactivity was detected in 7/23 cases (30%) and Tß10 reactivity in 22/23 (97%) cases analyzed, adding HCC to human cancers that express these beta-thymosins. Intriguing finding was seen looking at the reactivity of both peptides in tumor cells infiltrating the surrounding liver. Where Tß10 showed a strong homogeneous expression, was Tß4 completely absent in cells undergoing stromal invasion. The current study shows expression of both beta-thymosins in HCC with marked differences in their degree of expression and frequency of immunoreactivity. The higher incidence of Tß10 expression and its higher reactivity in tumor cells involved in stromal invasion indicate a possible major role for Tß10 in HCC progression.

Modifications of the acidic soluble salivary proteome in human children from birth to the age of 48months investigated by a top-down HPLC-ESI-MS platform.

During the first year of life the infant oral environment undergoes dramatic changes. To investigate how the salivary proteome of human children evolves during infant development we have analyzed whole saliva of 88 children aged between 0 and 48months by a top-down platform based on RP-HPLC-ESI-MS. Children were divided according to their age into five groups (A, 0-6months, N=17; B, 7-12months, N=14; C, 13-24months, N=32; D, 25-36months, N=16; E, 37-48months, N=9). The proteins and peptides analyzed were histatins (histatin-1, histatin-3 1/24), acidic proline-rich proteins, statherin, P-B peptide, and salivary cystatins. Protein and peptide quantification based on the area of the RP-HPLC-ESI-MS extracted ion current peak evidenced that: (i) concentrations of the major salivary proteins/peptides showed a minimum in the 0-6-month-old group and increased with age; (ii) the level of histatin-1 reached a maximum in the 7-12-month-old group, a minimum in the 13-24-month-aged babies and it increased again in the 25-36-month-old group; (iii) S-type cystatins were almost undetectable in the 0-6-month-old group; (iv) P-B peptide concentration greatly increased with age; (v) histatin-3 1/24 and statherin concentrations did not show any age-related variation. BIOLOGICAL SIGNIFICANCE: The top-down proteomic approach undertaken in this work reveals that the salivary proteome of human children from birth to 48months of age shows important quantitative modifications. The concentrations of the major salivary proteins, with the exception of statherin and histatin-3 1/24, showed a minimum in the 0-6-month-old group when the expression in salivary glands is probably not fully activated. Concentrations of the salivary proteins slowly increased with age, with different trends. Only histatin-1 showed the highest concentration in the 7-12-month-old group, followed by a decrease in the 13-24-month-aged children. This particular trend could be related to the phenomenon of eruption of primary dentition. This study gives a contribution to the knowledge on the physiological variability occurring in human saliva during the early childhood. It could represent a strong and reliable basis for further investigation of saliva to develop diagnostic and prognostic biomarkers.

Immunoreactivity for thymosin beta 4 and thymosin beta 10 in the adult rat oro-gastro-intestinal tract.

Thymosin beta 4 (Tß4) and thymosin beta 10 (Tß10) are two members of the ß-thymosin family, involved in multiple cellular activities in different organs in multiple animal species. Here we report the expression pattern of Tß4 and Tß10 in rat tissues, in the gut and in annexed glands. The two peptide were differently expressed: Tß4 was absent in salivary glands whereas Tß10 was expressed in parotid and in submandibular glands. Tß4 was mildly expressed in the tongue and in the oesophagus, where Tß10 was absent. A similar expression was found in the stomach, ileum and colon mucosa. In pancreas Tß4 reactivity was restricted to the Langerhans islet cells; Tß4 was also detected in the exocrine cells. Both peptide were not expressed in liver cells. When the rat expression pattern in rat organs was compared to reactivity for Tß4 and Tß10 in humans, marked differences were found. Our data clearly indicate a species-specific expression of Tß4 and Tß10, characterized by the actual unpredictability of the expression of these peptides in different cells and tissues. The common high expression of Tß4 in mast cells, both in humans and in rats, represents one of the few similarities between these two species.

Expression pattern of thymosin beta 4 in the adult human liver.

Thymosin beta-4 (Tß4) is a member of beta-thymosins, a family of small peptides involved in polymerization of G-actin, and in many critical biological processes including apoptosis, cell migration, angiogenesis, and fibrosis. Previous studies in the newborn liver did not reveal any significant reactivity for Tß4 during the intrauterine life. The aim of the present study was to investigate by immunohistochemistry Tß4 expression in the adult normal liver. Thirty-five human liver samples, including 11 needle liver biopsies and 24 liver specimens obtained at autopsy, in which no pathological change was detected at the histological examination, were immunostained utilizing an anti-Tß4 commercial antibody. Tß4 was detected in the hepatocytes of all adult normal livers examined. A zonation of Tß4 expression was evident in the vast majority of cases. Immunostaining was preferentially detected in zone 3, while a minor degree of reactivity was detected in periportal hepatocytes (zone 1). At higher power, Tß4-reactive granules appeared mainly localized at the biliary pole of hepatocytes. In cases with a strong immunostaining, even perinuclear areas and the sinusoidal pole of hepatocytes appeared interested by immunoreactivity for Tß4. The current work first evidences a strong diffuse expression of Tß4 in the adult human liver, and adds hepatocytes to the list of human cells able to synthesize large amounts of Tß4 in adulthood. Moreover, Tß4 should be added to the liver proteins characterized by a zonate expression pattern, in a descending gradient from the terminal vein to the periportal areas of the liver acinus. Identifying the intimate role played by this peptide intracellularly and extracellularly, in physiology and in different liver diseases, is a major challenge for future research focusing on Tß4.

Potential applications of human saliva as diagnostic fluid.

The use of human saliva as a diagnostic and prognostic fluid has until recently been somewhat disregarded. Although sample collection is non-invasive, physiological and genetic variations were largely responsible for its infrequent application in the past. Recently, several proteomic studies contributed to partial elucidation of the salivary proteome (more than 2400 protein components have been characterized), both in terms of composition, contributions to whole saliva and genetic/physiological variability. On this basis, is not too optimistic to believe that in the near future human saliva could become a relevant diagnostic fluid. In this review, the characterization by proteomic approaches of new salivary markers in oncology, head and neck carcinoma (oral cavity, oropharynx, larynx, and salivary glands), breast and gastric cancers, salivary gland function and disease, Sjögren syndrome, systemic sclerosis, dental and gingival pathology, systemic, psychiatric and neurological diseases, is described.

Proteomics of saliva: personal experience.

The salivary proteome is a complex protein mixture resulting from the activity of salivary glands with the contribution of other components that form the oral environment such as oral tissues and micro-organisms. For diagnosis purposes, saliva collection has the great advantage of being an easy and non-invasive technique. Human saliva proteomics have proven to be a novel approach in the search for protein biomarkers for detection of different local and systemic diseases. Currently, more than 1400 salivary proteins have been identified. In the last few years, our research group has extensively studied the salivary proteomics in order to analyse the salivary composition, investigating the major families of proteins present in human and mammalian saliva, the post-translational modifications, the different contributions of glands, the physiological and pathological modifications of saliva. The aim of this report is to present our personal experience in salivary proteomics. In conclusion, salivary proteome analysis represents an important field both for diagnosis and monitoring of various diseases and could be considered a novel approach to prevention of various pathological conditions.

Thymosin beta 4 expression in normal skin, colon mucosa and in tumor infiltrating mast cells.

Mast cells (MCs) are metachromatic cells that originate from multipotential hemopoietic stem cells in the bone marrow. Two distinct populations of MCs have been characterized: mucosal MCs are tryptase-positive while mast cells in skin contain tryptase and chymase. We now show that a sub-population of MCs is highly immunoreactive for thymosin beta4, as revealed by immunohistochemical analyses of normal skin, normal colon mucosa and salivary gland tumors. Four consecutive serial sections from each case were immunostained for thymosin beta4 (Tbeta4), chymase, tryptase and stained for toluidine blue. In skin biopsies, MCs showed a comparable immunoreactivity for Tbeta4, chymase and tryptase. In normal colon mucosa the vast majority of mucosal MCs expressed a strong cytoplasmic immunoreactivity for tryptase and for Tbeta4, in the absence of chymase reactivity. A robust expression of Tbeta4 was detected in tumor-infiltrating and peritumoral mast cells in salivary gland tumors and breast ductal infiltrating carcinomas. Tumor-infiltrating MCs also showed a strong immunoreactivity for chymase and tryptase. In this paper, we first demonstrate that normal dermal and mucosal mast cells exhibit strong expression of thymosin beta4, which could be considered a new marker for the identification of mast cells in skin biopsies as well as in human tumors. The possible relationship between the degree of Tbeta4 expression in tumor-infiltrating mast cells and tumor behaviour warrants further consideration in future investigations.

Immunoreactivity of thymosin beta 4 in human foetal and adult genitourinary tract.

Thymosins beta 4 (Tβ4) is a member of the beta-thymosins family, a family of peptides playing essential roles in many cellular functions. Our recent studies suggested Tβ4 plays a key role in the development of human salivary glands and the gastrointestinal tract. The aim of this study was to analyse the presence of Tβ4 in the human adult and foetal genitourinary tract. Immunolocalization of Tβ4 was studied in autoptic samples of kidney, bladder, uterus, ovary, testicle and prostate obtained from four human foetuses and four adults. Presence of the peptide was observed in cells of different origin: in surface epithelium, in gland epithelial cells and in the interstitial cells. Tβ4 was mainly found in adult and foetal bladder in the transitional epithelial cells; in the adult endometrium, glands and stromal cells were immunoreactive for the peptide; Tβ4 was mainly localized in the glands of foetal prostate while, in the adults a weak Tβ4 reactivity was restricted to the stroma. In adult and foetal kidney, Tβ4 reactivity was restricted to ducts and tubules with completely spared glomeruli; a weak positivity was observed in adult and foetal oocytes; immunoreactivity was mainly localized in the interstitial cells of foetal and adult testis. In this study, we confirm that Tβ4 could play a relevant role during human development, even in the genitourinary tract, and reveal that immunoreactivity for this peptide may change during postnatal and adult life.

alpha-Defensin levels in whole saliva of totally edentulous subjects.

Salivary levels of alpha-defensins 1-4 and histatins 1, 3 and 5 were determined in 11 totally edentulous patients, 11 younger healthy adults with normal gingival mucosa (Control group I) and 8 subjects, age-matched with edentulous patients, having a minimum of 25 teeth (Control group II). Whole saliva was treated with trifluoroacetic acid and the acidic soluble fraction analyzed by High Performance Liquid Chromatography-Mass Spectrometry. The area of the extracted ion current peaks was used for peptide quantification. Levels of alpha-defensins1-4, but not of histatins, were significantly lower in totally edentulous patients with respect to both Control group I and Control group II. The two control groups did not show significant differences. The reduced level of oral alpha-defensins, which are mainly of crevicular origin, is most likely due to the absence of the gingival sulcus in the edentulous subjects. The near absence of alpha- defensins might be in part responsible for the higher vulnerability of the oral cavity to oral pathogen infections observed in totally edentulous patients.

Structural and functional characterization of the porcine proline-rich antifungal peptide SP-B isolated from salivary gland granules.

A 1905-Da cationic proline-rich peptide, named SP-B, was recently isolated by our group as the main component of salivary gland granules, and its primary sequence fully characterized by means of automated Edman sequencing and LC-MS/MS tools. In the present study SP-B is shown to possess antifungal activity when challenged with strains of Cryptococcus neoformans, Candida albicans and Aspergillus fumigatus, while only negligible antibacterial activity was detected. Furthermore, SP-B was found to be non-cytotoxic when tested on fibroblast cell lines. To obtain information regarding its structure affinity, capillary electrophoresis (CE), circular dichroism (CD) and attenuated total reflection (ATR)-FT/IR experiments were performed. CE revealed a pH dependence of the hydrodynamic radial dimensions both in aqueous and 2,2,2-trifluoroethanol solutions. CD and ATR-FT/IR measurements confirmed the structure-pH relationship, revealing a secondary structure composed of mixed proportions of polyproline-II, unordered and turn motifs, the last being more evident in the zwitterionic form of the peptide. From these findings SP-B peptide could be classified as a new member of the proline-rich antimicrobial peptide family.

Proteomic study of salivary peptides and proteins in patients with Sjögren's syndrome before and after pilocarpine treatment.

OBJECTIVE: To investigate the effect of pilocarpine on the salivary peptide and protein profile in patients with primary Sjögren's syndrome (SS) and to study the differences between patients with primary SS, patients with SS associated with other rheumatic diseases, and healthy control subjects. METHODS: Saliva specimens were obtained from 9 primary SS patients, 9 secondary SS patients, and 10 healthy controls. Samples were analyzed for levels of 62 different salivary proteins using high-performance liquid chromatography coupled with mass spectrometry using a spectrometer equipped with an electrospray ionization source. In 6 of the primary SS patients, saliva was collected at 30 minutes, 60 minutes, and 24 hours after taking 5 mg of pilocarpine. RESULTS: Before pilocarpine, approximately 60% of salivary proteins in samples from primary SS patients were not identifiable or showed lower levels than those in healthy controls. After 30-60 minutes following pilocarpine treatment, approximately one-third of the less represented proteins was found in a similar percentage of primary SS patients and controls. Almost all of the proteins that were detectable at lower levels in primary SS patients compared with controls reached levels similar to those in controls at 30-60 minutes after pilocarpine. The parotid gland proteins had the best response to pilocarpine. Primary SS patients were characterized by higher alpha-defensin 1 levels and by the presence of beta-defensin 2. Secondary SS patients showed an intermediate protein profile between that of the primary SS patients and the controls. CONCLUSION: Pilocarpine partially restored the levels and numbers of identifiable proteins in saliva from patients with primary SS. Higher levels of alpha-defensin 1 and the presence of beta-defensin 2 in the saliva of patients with primary SS could be markers of oral inflammation in this patient group.

Two proline-rich peptides from pig (Sus scrofa) salivary glands generated by pre-secretory pathway underlying the action of a proteinase cleaving ProAla bonds.

The primary structures of two salivary proline-rich peptides (PRP-SP-A, M 6156.0 amu and PRP-SP-B, M 1905.0 amu), from pig (Sus scrofa) were determined. The PRP-SP-B peptide, 21 residues long, overlaps with a sequence repeated 43 times in three deposited cDNAs coding for PRP proteins cloned from porcine parotid glands (Swiss-Prot codes: Q95JC9, Q95JD1, Q95JD0). PRP-SP-A peptide, 56 amino acid residues long, overlaps with the N-terminus repeats of Q95JC9 and Q95JD1 and it is phosphorylated at Ser 12 and 14. The two peptides were found both in whole saliva and in granules from pig parotid glands. The biosynthesis of the two peptides implies the action of a proteinase responsible for Pro downward arrow Ala cleavage in the pre-secretory process.

Statherin levels in saliva of patients with precancerous and cancerous lesions of the oral cavity: a preliminary report.

OBJECTIVE: The aim of this study was to measure concentration of human salivary statherin in patients with oral cavity pathologies and salivary gland diseases. SUBJECTS AND METHODS: Levels of statherin were analysed with High Performance Liquid Chromatography (HPLC) in following groups of subjects: group A: 24 patients with neoplastic diseases of salivary glands, group B: 13 patients with inflammatory lesions of salivary glands, group C: 13 patients with precancerous and cancerous lesions of the oral cavity excluding salivary gland tumors, group D: 20 healthy volunteers (control group). RESULTS: Our preliminary data indicated a sensible reduction of the statherin level in the saliva of patients with precancerous and cancerous lesions of the oral cavity (group C) compared with the healthy subjects (group D). The statherin levels are not significantly reduced either in the inflammatory (group B) or in the salivary glands tumours (group A), compared with the healthy subjects (group D). CONCLUSION: Statherin could play a protective effect in oral cavity in association with its other functions.

Bezafibrate induces a mitochondrial derangement in human cell lines: a PPAR-independent mechanism for a peroxisome proliferator.

Bezafibrate is a hypolipidemic drug that belongs to the group of peroxisome proliferators because it binds to peroxisome proliferator-activated receptors type alpha (PPARs). Peroxisome proliferators produce a myriad of extraperoxisomal effects, which are not necessarily dependent on their interaction with PPARs. An investigation on the peculiar activities of bezafibrate could clarify some of the molecular events and the relationship with the biochemical and pharmacological properties of this class of compounds. In this view, the human acute promyelocytic leukemia HL-60 cell line and human rabdomiosarcoma TE-671 cell line were cultured in media containing bezafibrate and a number of observations such as spectrophotometric analysis of mitochondrial respiratory chain enzymes, NMR metabolite determinations, phosphofructokinase enzymatic analysis, and differentiation assays were carried on. Bezafibrate induced a derangement of NADH cytochrome c reductase activity accompanied by metabolic alterations, mainly a shift to anaerobic glycolysis and an increase of fatty acid oxidation, as shown by NMR analysis of culture supernatants where acetate, lactate, and alanine levels increased. On the whole, the present results suggest a biochemical profile and a therapeutic role of this class of PPARs ligands more complex than those previously proposed.

Human salivary peptides derived from histatins.

Human saliva from a healthy donor was subjected to fractionation by gel chromatography and six pools were collected and analysed by MALDI-TOF-MS and HPLC-ESI-MS. Three peptides, corresponding to 888.3, 687.3, and 524.1 amu and SNYLYDN, YLYDN, and LYDN sequences (determined by automated Edman sequencing), were isolated from pool 4. YLYDN was not previously described in human saliva. The peptides show the common C-terminal sequence of histatin 3 and histatin 1. To exclude the possibility that the three peptides were an artifact of the purification procedure, nine samples of human saliva were collected from healthy donors, immediately acidified with 0.2% TFA, and analysed by RP-HPLC-ESI-MS. The three peptides were detected in all the analyzed samples. SNYLYDN was always found at a concentration higher than that of YLYDN and LYDN. A correlation analysis performed on quantitative data indicated that the three peptides derive only from histatin 3. Other already known histatins also were searched for in the chromatogram. Histatins 1, 2, 3, 5, 6, 7, 8, and 10 were observed, although not in all samples analyzed, whereas other minor histatins were not detected.

The coupling of RP-HPLC and ESI-MS in the study of small peptides and proteins secreted in vitro by human salivary glands that are soluble in acidic solution.

The aim of this study was the development of a method based on the coupling of RP-HPLC and ESI-MS for identifying and quantifying proteins and peptides secreted by human salivary glands in vitro. Salivary gland specimens, obtained from informed patients undergoing surgical resection, were incubated in an optimized medium. Incubation media of glandular specimens, selected on the basis of cytomorphological and ultrastructural analysis, were investigated by HPLC-MS. Several salivary peptides/proteins, previously recognized in human whole saliva, were searched for along the chromatogram by the selected ion monitoring (SIM) strategy. Analysis of the incubation media of parotid glands revealed the presence of basic PRPs PC, PD, PH, IB-1, II-2, and acidic PRP-1 and PRP-3 in all of the investigated samples. Basic PRPs PB and PA, acidic PRPs, and cystatins SN and S1 were detected in all of the incubation media of submandibular glands, whereas histatin 1 was detected in only one sample. Moreover, the method allowed detection of some post-translational derivatives of known salivary proteins, as well as of several previously unidentified small peptides. The present method represents a sensitive and powerful instrument to detect peptides and proteins secreted by human salivary glands in vitro.

Role of ergothioneine on S-nitrosoglutathione catabolism.

Ergothioneine (ESH) is a low-molecular-mass thiol present in millimolar concentrations in a limited number of tissues, including erythrocytes, kidney, seminal fluid and liver; however, its biological function is still unclear. In the present study we investigated the role of ESH in the catabolism of S-nitrosoglutathione (GSNO). The results show that: (1) GSNO decomposition is strongly influenced by ESH (k"=0.178+/-0.032 M(-1) x s(-1)); (2) ammonia is the main nitrogen-containing compound generated by the reaction; and (3) nitrite is practically absent under both aerobic and anaerobic conditions. These findings are markedly different from those reported for the GSH-induced decomposition of GSNO, in which the nitrogen-containing end products are nitrite, ammonia and nitrous oxide (N(2)O) under aerobic conditions but nitrite, ammonia, nitric oxide (NO) and small quantities of hydroxylamine under anaerobic conditions. Considering the high concentration of ESH in specific cells, the reaction with GSNO should be considered as an important molecular event occurring in the cell.