Biomedical subjects

C Goso

Publications and source records attributed to C Goso.

At least 19 recordsLinked to original sources

PubMed2002

Novel anthracycline oligosaccharides: influence of chemical modifications of the carbohydrate moiety on biological activity.

Several observations highlight the importance of the carbohydrate moiety for the biological activity of antitumoural anthracyclines. Here is reported the synthesis, cytotoxicity and topoisomerase II-mediated DNA cleavage intensity of the new oligosaccharide anthracyclines 1--4 modified in the sugar residue. Evaluation of cytotoxic potency on different cell lines, resulted in quite similar values among the different analogues. On the other hand, topoisomerase II-mediated DNA breaks level was different for the various compounds, and was not related to cytotoxicity, thus supporting previous observations reported for some monosaccharide anthracyclines modified in the carbohydrate portion.

Antibiotics, Antineoplastic↗

PubMed2001

A comparative study of cellular and molecular pharmacology of doxorubicin and MEN 10755, a disaccharide analogue.

MEN 10755 is a disaccharide anthracycline endowed with a broader spectrum of antitumour activity than doxorubicin (DOX). To investigate the cellular and molecular basis of its action, cytotoxic activity, drug uptake, subcellular localisation, induction of DNA damage, and apoptosis were assessed in the human A2780 ovarian carcinoma cell line. Experiments with radiolabelled anthracyclines indicated that MEN 10755 exhibited reduced cellular accumulation and a different subcellular distribution (higher cytoplasmic/nuclear ratio) than DOX. In spite of the lower nuclear concentration, MEN 10755 was as potent as DOX in eliciting DNA single- and double-strand breaks, G2/M cell arrest, and apoptosis. Sequencing of drug-induced topoisomerase II cleavage sites showed a common DNA cleavage pattern for MEN 10755 and DOX. Cleavage sites were always characterised by the presence of adenine in -1 position. However, the extent of DNA cleavage stimulation induced by MEN 10755 was greater than that produced by DOX. Reversibility studies showed that MEN 10755-stimulated DNA cleavage sites were more persistent than those induced by DOX, thus suggesting a more stable interaction of the drug in the ternary complex. As a whole, the study indicated that the cellular pharmacokinetics of MEN 10755 substantially differs from that of DOX, showing a lower uptake and a different subcellular disposition. In spite of the apparently unfavourable cellular pharmacokinetics, MEN 10755 was still as potent as DOX in inducing topoisomerase-mediated DNA damage. Although the extent and persistence of protein-associated DNA breaks may contribute to the cytotoxic effects, the drug's efficacy as apoptosis inducer and antitumour agent could not be adequately explained on the basis of DNA damage mediated by the known target (i.e. topoisomerase II), thus supporting additional cellular effects that may be relevant in cellular response.

Antineoplastic Agents↗

PubMed2001

Cardioprotective effects of zofenopril, a new angiotensin-converting enzyme inhibitor, on doxorubicin-induced cardiotoxicity in the rat.

We have studied the effect of zofenopril, a new angiotensin-converting enzyme inhibitor in preventing cardiac injury induced by chronic doxorubicin treatment in rats. Cardiac function was assessed by measuring changes in electrocardiogram (ECG) tracings, haemodynamics and cardiac responses in vivo to isoprenaline, 4 weeks after suspension of doxorubicin treatment, in vehicle-treated rats and in animals receiving zofenopril (15 mg/kg/os/day) alone, doxorubicin (1.5 mg/kg i.v. once a week for 5 weeks) or zofenopril+doxorubicin treatment. Doxorubicin induced a significant lengthening of the QalphaT interval, which was completely prevented by zofenopril treatment. The cardiac positive inotropic effect induced by i.v. isoprenaline was selectively depressed by doxorubicin (no changes in chronotropic responses) and this adverse effect of doxorubicin was also prevented in zofenopril+doxorubicin pretreated rats. Doxorubicin induced a significant increase in relative heart weight, which was likewise prevented in zofenopril+doxorubicin treated rats. In separate experiments, zofenopril did not interfere with the antitumor activity of doxorubicin (inhibition of tumor growth in nude mice xenografted with A2780 human tumor line). In conclusion, the oral administration of zofenopril is able to significantly ameliorate, up to 4 weeks after the end of doxorubicin administration, doxorubicin-induced cardiotoxicity without affecting the antitumor activity of this anthracycline.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2001

Anthracyclines: selected new developments.

Anthracycline antibiotics play an important role in cancer chemotherapy. The need for an improvement of their therapeutic index has stimulated an ongoing search for anthracycline analogues with improved properties. Analogue development was originally limited by a lack of information on the cellular drug target, nevertheless almost 20 years ago the mechanism of action of doxorubicin and daunorubicin was revealed and DNA topoisomerase II was recognised to be their main cellular target. Several anthracyclines interfere with topoisomerase II functions by stabilizing a reaction intermediate in which DNA strands are cut and covalently linked to tyrosine residues of the enzyme. Investigations on the sequence specificity of doxorubicin in vitro and in nuclear chromatin of living cell have led to a molecular model of drug receptor on the topoisomerase II-DNA complex. Anthracyclines are likely placed at the interface between the DNA cleavage site and the active site of the enzyme, forming a DNA-drug-enzyme ternary complex. Moreover, a quite detailed structure-function relationship has been established for anthracyclines. First, drug intercalation is necessary but not sufficient for topoisomerase II poisoning; second, the removal of the 4-methoxy and 3'-amino substituents greatly increases the drug activity and third, the 3' substituent of the sugar moiety markedly influences the sequence selectivity of anthracycline-stimulated DNA cleavage. These relationships have been exploited during the last decade by several groups, including ours, in the search for new anthracycline drugs with lower side effects and higher activity against resistant cancer cells. This review will focus on areas of the anthracycline field including synthesis of new analogues, new strategies of synthesis and recent developments in the area of drug delivery.

Animals↗

PubMed2001

Apoptotic events in a human ovarian cancer cell line exposed to anthracyclines.

Cytotoxic drugs commonly used in cancer therapy promote tumor cell death by inducing apoptosis, but the cell death pathway(s) is likely dependent on the mechanism of drug action. In the present study, we investigated the mechanisms of cell death induced by doxorubicin (DXR) and the novel disaccharide anthracycline MEN 10755, in a human ovarian cancer cell line (A2780). Exposure to either anthracycline induced the up-regulation of several genes known to promote cell cycle arrest and DNA repair (WAF1/p21, GADD45) or apoptosis (bax, Fas). Although the expression of Fas was increased, an antagonistic anti-Fas antibody ZB4 did not inhibit anthracycline-induced apoptosis, suggesting that the stimulation of the Fas receptor did not play a critical role in the induction of apoptosis in this cell line. We also observed that neither MEN 10755 nor DXR were able to induce apoptosis in A2780 cells deprived of the nucleus but retaining an intact mitochondrial function (cytoplasts) and that apoptosis induced by either anthracycline was inhibited by cycloheximide, indicating that it is an active process requiring new protein synthesis. Both the caspases inhibitors, ZVAD-fmk and DEVD-cho, inhibited at similar extent apoptosis induced by either DXR or MEN 10755, suggesting an involvement of caspase-3 in this response. We conclude that, in a tumor cell line of epithelial origin, the apoptosis following exposure to anthracyclines is an active process requiring protein synthesis and drug interaction with nuclear structures. The pathway was Fas-independent but likely involved bax and caspase-3 as effectors of the cascade culminating in apoptosis.

Annexins↗

PubMed1998

Changes in the amount and level of phosphorylation of p56(lck) in PBL from aging humans.

The effects of aging on the activation of the cytoplasmic tyrosine protein kinase p56(lck) have been investigated in PBL from adult and elderly subjects upon activation with mitogens or different co-stimuli. Results show that the amount and phosphorylation of p56(lck) are reduced in PBL from elderly as compared to adult subjects. This finding suggests that alterations in p56(lck) may contribute to the age-associated loss of some T cell functions, such as proliferation and IL-2 production, which are found decreased in PBL from old individuals. However, p56(lck) seems irrelevant to the production of IFN-gamma and IL-4 which were both found increased in the PBL from old subjects, as expected from the relative expansion of memory versus naive T cell subpopulations in aging.

Adult↗

PubMed1998

Cell proliferation and ku protein expression in ageing humans.

Previous studies on DNA repair in ageing have demonstrated increased frequencies of single and double strand breaks in lymphocytes from elderly subjects and, as a consequence, decreased efficiency in DNA replication. We have investigated the relationship between cell proliferation and the nuclear expression of ku protein in a human population of 43 subjects of different ages. Ku is an heterodimeric protein composed of two subunits of 70 and 80 kDa, which is involved in the early steps of DNA damage recognition. In the present study, PBL from subjects of different ages were PHA-activated to evaluate the stimulation index and the production of Th1- and Th2-type cytokines. Moreover, nuclear extracts were obtained from activated lymphocytes to evaluate by a gel retardation assay the presence and the functional activity of the heterodimer ku 70/80. Our results indicate that ageing affects the mitotic responsiveness and cytokine production to a significant extent, but only marginally the expression of ku 70/80. These findings suggest that the age-related impairment in DNA repair mechanisms are only in part related to the reduced expression of ku protein able to recognize DNA damage.

Adult↗

PubMed1997

Regulation of cytokine production in aging: use of recombinant cytokines to upregulate mitogen-stimulated spleen cells.

We investigated the production of IL-2 and IFN-gamma (Th1 type) and IL-4 (Th2 type) cytokines by mitogen-activated spleen cells from young, adult and old mice. Cytokine production was evaluated in culture supernatants by CTLL proliferation (IL-2), ELISA (IFN-gamma), CT4.S proliferation (IL-4) and in mRNA extracted from activated CD4+ cells by RT-PCR (IL-2, IFN-gamma and IL-4). Results show that the production of IL-2, as protein and mRNA, is profoundly depressed by aging, whereas that of IFN-gamma, as protein and mRNA, firstly declines and then increases with age. The production of IL-4, as protein, monotonically declines with aging whereas, as mRNA, firstly decreases and then increases above the level in young mice. Spleen cells in culture were also incubated with mitogens and with a recombinant cytokine (IL-1 beta, IL-2, IL-3, IL-4, IL-12 or IFN-gamma) at various concentrations. It was found that recombinant cytokines by and large enhance cytokine production when the level induced by mitogens only is low. This conclusion applies to IL-2 and IFN-gamma production as protein and mRNA. The addition of recombinant cytokines also increases the production of IL-4 at the protein level in spleen cells from old mice but, at the mRNA level, only in spleen cells from young mice. This finding suggests age-related changes in IL-4-specific mRNA transcription rate and post-transcriptional half-life as well as translation kinetics.

Aging↗

PubMed1995

[3H][beta-Ala8]neurokinin A-(4-10): a novel, selective radioligand for the tachykinin NK2 receptor.

The binding characteristics of the novel radioligand [3H][beta-Ala8]neurokinin A-(4-10) were assessed in hamster urinary bladder membranes. This labelled compound bound in a reversible, highly specific and concentration-dependent manner to a single class of high affinity binding sites with a Kd of 1.8 +/- 0.2 nM and a Bmax of 139 +/- 21 fmol/mg of protein. Specific binding of [3H][beta-Ala8]neurokinin A-(4-10) was displaced only by NK2, but not by NK1 or NK3, tachykinin receptor agonists and antagonists. Neurokinin A, [beta-Ala8]neurokinin A-(4-10), L 659877 [cyclo(Leu-Met-Gln-Trp-Phe-Gly)], MEN 10376 (H-Asp-Tyr-D-Trp-Val-D-Trp-D-Trp-Lys-NH2), MEN 10627 [cyclo(Met-Asp-Trp-Phe-Dap-Leu)cyclo(2 beta-5 beta)] and SR 48968 [(S)-N-methyl-N-[4-(4-acetylamino-4-phenylpiperidino)-2- (3,4-dichlorophenyl)butyl]benzamide] displaced the binding with Ki values of 0.4 +/- 0.1 nM, 1.9 +/- 0.36 nM, 3.05 +/- 0.1 nM, 7.9 +/- 0.4 microM, 0.36 +/- 0.02 nM and 2.5 +/- 0.9 nM, respectively. Functional data, obtained in isolated hamster urinary bladder strips with the newly developed tachykinin NK2 receptor antagonists (MEN 10627 and SR 48968), showed a good agreement with binding data. This novel radioligand could represent a new useful tool for the assessment of tachykinin NK2 receptor antagonists.

Animals↗

PubMed1995

Synthesis and biological evaluation of novel NK-1 tachykinin receptor antagonists: the use of cycloalkyl amino acids as a template.

In the course of a program aimed at synthesizing novel, potent NK-1 tachykinin receptor antagonists, we developed upon a bioactive model by comparing the low energy structures of a series of peptide and nonpeptide Substance P antagonists. The comparison was based on the superimposition of the aromatic rings, assuming that the rest of the molecule behaves predominantly as a template to arrange the key aromatic groups in the right spatial position. A series of 2-aminocyclohexane carboxylic acid analogues were then selected as the best templates for reproducing the postulated bioactive structure, leading to several pseudo-peptides with interesting biological activity. According to the molecular modeling, these compounds exhibit a neat parallel facing of the indolyl and naphthyl groups at about 3 A distance. Ultraviolet absorption and steady state fluorescence measurements support this conclusion, showing a linear correlation between the spectral properties and the binding affinity of these analogues. Stacking of the indole ring with naphthalene gives rise to a complex characterized by a well-defined molar extinction coefficient. Consistently, steady state and lifetime fluorescence measurements suggest that the quenching process is ascribable to ground-state interactions between the chromophores. Implications of the pi stacking propensity of aromatic groups in the biological activity of the compounds examined are briefly discussed.

Amino Acids↗

PubMed1995

Resiniferatoxin binding to vanilloid receptors in guinea pig and human airways.

We have used the [3H]resiniferatoxin (RTX) binding assay to characterize for the first time a vanilloid (capsaicin) receptor in tracheobronchial tissues of the guinea pig. Membranes obtained from the trachea and the main bronchi bound RTX with an affinity of 1 nM; the cooperativity index was close to unity, indicating noncooperative binding. Specific [3H]RTX binding was fully inhibited by capsaicin (Ki = 500 nM) and capsazepine (Ki = 100 nM), but it was not inhibited at all by the inactive RTX structural analog resiniferonol 9, 13, 14-orthophenylacetate (10 microM), confirming the specificity of the binding. Neither was RTX binding inhibited by the functional vanilloid antagonist ruthenium red (100 microM). The density of specific RTX binding sites was similar in the trachea (Bmax = 150 fmol/mg protein) and the bronchi (Bmax = 170 fmol/mg protein). In keeping with the marked resistance of hamsters to capsaicin actions, no specific RTX binding could be detected in the airways of this species. By contrast, we have been able to demonstrate specific RTX binding sites in human bronchi: the estimated affinity for RTX, 2 nM, was similar to that (7 nM) determined in guinea pig bronchi. We conclude that (1) the [3H]RTX binding assay affords a novel biochemical marker for vanilloid-sensitive nerves in the airways, and (2) this binding assay may be a useful tool to explore species-related differences in the expression and pharmacologic profile of vanilloid receptors in the airways.

Adult↗

PubMed1995

Activity of cyclic pseudopeptide antagonists at peripheral tachykinin receptors.

The cyclic pseudopeptides MEN 10,548, MEN 10,581, MEN 10,619, MEN 10,677, MEN 10,777 and MEN 10,867 were studied at tachykinin neurokinin (NK)1, NK2 and NK3 receptors on several in vitro bioassays. All compounds were potent and competitive antagonists at tachykinin NK1 and NK2 receptors of the guinea-pig ileum, rabbit pulmonary artery and hamster trachea, showing the highest affinity for the hamster NK2 receptor (e.g., MEN 10,677: pKB = 9.3). By contrast, none showed affinity for NK3 receptors of the rat portal vein, up to 3 microM. In the guinea-pig isolated bronchus, the pseudopeptide compounds competitively antagonized the NK2 receptor-selective agonist [beta Ala8]-NKA (4-10) with potencies comparable to those shown at the rabbit NK2 receptor. In addition, the pseudopeptides were from 3.5-fold (MEN 10,677) to 16-fold (MEN 10548) more potent antagonists against septide than against [Sar9]SP sulfone, two agonists reportedly selective for two distinct sites/subtypes of the NK1 receptor. In binding experiments at human IM9 cells, the pseudopeptide compounds displaced [3H]substance P from human NK1 receptor, showing similar affinities to those displayed at the NK1 receptor in the guinea-pig ileum or bronchus against substance P methylester or septide, as agonists, respectively. This new class of pseudopeptide antagonists, by showing a comparable and high affinity at both tachykinin NK1 and NK2 receptors, might be proposed for treatment/prevention of airway diseases in which endogenous tachykinins play a role by activation of both receptors.

Amino Acid Sequence↗

PubMed1994

Different susceptibility to neurokinin 1 receptor antagonists of substance P and septide-induced interleukin-6 release from U373 MG human astrocytoma cell line.

In a human astrocytoma cell line U373 MG, the activation of the neurokinin 1 (NK1) receptor by substance P (SP) increase, in a concentration-related manner (1 nM to 10 microM), the basal release of interleukin-6 (IL-6) as assayed by an ELISA method, in cell supernatants after 18 h of incubation. Septide, a selective NK1 receptor agonist, is equipotent to SP in inducing the IL-6 release showing similar Emax (2644 +/- 285 and 2830 +/- 271 pg/ml) and EC50 (15.6 +/- 3.6 and 13.8 +/- 3.2 nM). However, in binding assays on intact cells, septide was an about 50-fold weaker displacer of the binding of [3H][Sar9,Met(O2)11]SP than SP (Ki's were 0.28 +/- 0.1 nM and 14.2 +/- 5.0 nM for SP and septide, respectively). NK2- and NK3-selective agonists (up to 1 microM) had no binding or functional effect. Highly selective non-peptide (CP96,345) or peptide (GR82,334) NK1 receptor antagonists were more effective in antagonizing septide-(IC50's 0.2 +/- 0.06 nM and 70 +/- 18 nM) than SP-(IC50's 6.7 +/- 1.3 nM and 1.95 +/- 0.4 microM) induced IL-6 secretion. These data support the existence, also in human U373 MG cells, of a septide-sensitive NK1 receptor subtype(s) and/or epitope(s) blocked with high affinity by NK1 antagonist.

Astrocytoma↗

PubMed1994

Comparison of tachykinin NK1 receptors in human IM9 and U373 MG cells, using antagonist (FK888, (+/-)-CP-96,345, and RP 67580) binding.

We have used one peptide (FK888) and two non-peptide ((+/-)-CP-96,345 and RP 67580) antagonists, along with the preferred endogenous agonist, substance P, to compare the pharmacological (binding) profile of NK1 receptors expressed by human B lymphoblastoma (IM9) and astrocytoma (U373 MG) cells. Of the ligands tested, substance P was the most potent in both cell lines: binding affinities were 0.1 nM for IM9 cells, and 0.3 nM for U373 MG cells, respectively. The high-affinity dipeptide antagonist, FK888, bound to NK1 receptors in both cell lines with similar potencies: Ki values were 1.2 nM and 3.6 nM for IM9 cells and U373 MG cells, respectively. Of the non-peptide antagonists, as expected, (+/-)-CP-96,345 displayed higher affinity (0.4 nM in IM9 cells, and 1.2 nM in U373 MG cells) than did RP 67580 (33 nM and 223 nM in IM9 cells and U373 MG cells, respectively) in both cell lines. We conclude that the pharmacological profile of NK1 receptors is similar in the human lymphoblastoma and astrocytoma cells, i.e. if NK1 receptor subtypes exist in humans, these cell lines are likely to express a similar subtype. Because IM9 cells grow faster and are easier to maintain, this cell line may be preferable to the astrocytoma cells as a primary screen to identify NK1 receptor antagonists.

Astrocytoma↗

PubMed1994

Characterization by [3H]resiniferatoxin binding of a human vanilloid (capsaicin) receptor in post-mortem spinal cord.

Membranes obtained from post-mortem human spinal cord specimens bound [3H]resiniferatoxin (RTX) with an affinity of 11 nM in a non-cooperative fashion. This binding behaviour contrasted with the high affinity [3H]RTX binding (Kd = 24 pM) to rat spinal cord membranes which displayed apparent positive cooperativity (cooperativity index = 1.8) but was in accord with the low affinity (Kd = 5 nM) non-cooperative RTX binding to guinea pig spinal cord preparations. We conclude that the [3H]RTX binding assay utilizing post-mortem human spinal cord membranes affords a novel biochemical approach to explore structure-activity relations at human vanilloid receptors.

Animals↗

PubMed1994

MEN 10,627, a novel polycyclic peptide antagonist of tachykinin NK2 receptors.

We describe the in vitro and in vivo pharmacological properties of MEN 10,627 or cyclo(Met-Asp-Trp-Phe-Dap-Leu)cyclo(2 beta-5 beta), the first example of a polycyclic peptide tachykinin NK2 receptor antagonist. MEN 10,627 is endowed with high affinity for NK2 receptor expressed in various species with pKB values ranging between 10.1 (hamster trachea) and 8.1 (rabbit pulmonary artery). The antagonism is of competitive type in both functional and radioligand binding assays. A 100- to 10,000-fold selectivity was found vs. NK1 or NK3 receptors expressed in various species. As an NK2 receptor antagonist, MEN 10,627 is 10- to 100-fold more potent than the monocyclic peptide antagonist L 659,877 or cyclo(Met-Gln-Trp-Phe-Gly-Leu). At the hamster NK2 receptor, MEN 10,627 is about 30-fold more potent than the nonpeptide NK2 receptor antagonist SR 48,968 [(S)-N-methyl-N[4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl) butyl]benzamide], whereas the converse is true for the rabbit NK2 receptor. Furthermore, MEN 10,627 is, up to micromolar concentrations, devoid of antagonist properties toward a wide range of transmitters of both peptide and nonpeptide nature. In urethane-anesthetized rats in vivo, MEN 10,627 (10-100 nmol/kg i.v.) produced long-lasting inhibition of contraction of the urinary bladder and duodenum produced by i.v. administration of the NK2 receptor agonist [beta Ala8]NKA(4-10), without affecting the responses produced by i.v. administration of the NK1 receptor agonist [Sar9]SP sulfone or acetylcholine. In anesthetized rats, both MEN 10,627 and SR 48,968 blocked urinary bladder contraction induced by the NK2 receptor agonist after intravenous, intranasal or intraduodenal administration. Equieffective doses of MEN 10,627 producing about 50% inhibition of the response to [beta Ala8]NKA(4-10) in the rat urinary bladder in vivo, were 0.01, 0.03 and 3 mumol/kg after intravenous, intranasal and intraduodenal administration, respectively. The corresponding doses of SR 48,968 were 0.03, 0.1 and 1 mumol/kg, after intravenous, intranasal and intraduodenal administration, respectively. In conclusion, MEN 10,627 is a potent and selective NK2 receptor antagonist, endowed with high potency and long duration of action in vivo, which is not restricted to parenteral administration.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1993

Resiniferatoxin-induced loss of vanilloid receptors is reversible in the urinary bladder but not in the spinal cord of the rat.

Resiniferatoxin (RTX) induced a dose-dependent loss of vanilloid receptors (specific [3H]RTX-binding sites) in tissues containing peripheral (urinary bladder) and central (spinal cord) endings of capsaicin-sensitive neurons. This receptor loss in the spinal cord was entirely due to a reduction in the Bmax. When examined 24 h after s.c. RTX treatment, receptor loss required somewhat less RTX in the urinary bladder (ED50 = 10 micrograms/kg) than in the spinal cord (ED50 = 50 micrograms/kg), whereas the loss of the xylene-induced neurogenic inflammatory response in the bladder displayed an approximate ED50 of 5 micrograms/kg. In the bladder of rats pretreated with 30 micrograms/kg RTX, both receptor binding and neurogenic inflammatory response recovered almost completely within 2 month after treatment. In the bladder of rats that received a 10-fold higher RTX dose, a 50% recovery of binding and a 70% recovery of the Evans' blue extravasation response were found. By contrast, no recovery of specific [3H]RTX binding to spinal cord membranes was observed at either dose. These findings suggest that vanilloid receptor loss after RTX treatment can be either reversible (desensitization) or irreversible (most likely reflecting neurotoxicity), and that peripheral and central terminals of capsaicin-sensitive neurons have a differential sensitivity to these long-term vanilloid actions.

Animals↗

PubMed1993

Topical capsaicin administration protects against trinitrobenzene sulfonic acid-induced colitis in the rat.

We used the [3H]resiniferatoxin binding assay to demonstrate for the first time the existence of vanilloid receptors in the rat colon and to explore their expression during trinitrobenzene sulfonic acid-induced colitis. Membranes obtained from control colon bound [3H]resiniferatoxin with an affinity of 3 nM; the receptor density was 450 fmol/mg protein or 9 fmol/mg wet weight. Capsaicin and capsazepine, a competitive antagonist of capsaicin, inhibited specific resiniferatoxin binding with Ki values of 3 microM and 0.1 microM, respectively. Trinitrobenzene sulfonic acid induced a very rapid ulceration in the colon: 1 h after treatment 90% of the colon showed ulcerative damage. Coadministration of 640 microM capsaicin diminished the ulcerative effect of trinitrobenzene sulfonic acid to 64% when examined 1 h after trinitrobenzene sulfonic acid challenge; however, this protective action was lost 23 h later. Colon samples obtained 4 h, 24 h, and 1 week after trinitrobenzene sulfonic acid challenge bound resiniferatoxin, capsaicin, and capsazepine with affinities similar to those of control samples. The receptor density remained at an essentially constant level when expressed in fmol/mg protein but, in keeping with the increased wet weights, showed a reduction when expressed in fmol/mg wet weight. We conclude that acute capsaicin administration protects against the ulcerative action of trinitrobenzene sulfonic acid, most likely via the release of protective neuropeptides from capsaicin-sensitive nerve endings. The loss of this protective action is presumably due to a depletion of the protective neuropeptides rather than to a loss of vanilloid (capsaicin) receptors.

Administration, Topical↗