RESUMEN
Inflammatory bowel disease (IBD), consisting of ulcerative colitis (UC) and Crohn's disease (CD), is a chronic relapsing and life-threatening inflammatory disorder that mainly affect the intestinal tract. The mainstream therapies for moderate to severe IBD lie in the use of immunosuppressive agents. However, it encountered the problem of drug tolerance and significant adverse events. Therefore, identifying novel signal pathways involved in IBD is necessary to satisfy the unmet treatment needs of IBD patients. There existed some hints between iron and IBD, and was reported that ferroptosis induced in UC. However, as another important subtype of IBD, whether ferroptosis also occurred in CD remains unclear. In this study, we found that the dysregulation of iron, lipid peroxidation and redox homeostasis were involved in CD; the administration of ferroptosis inhibitor Ferrostatin-1 could alleviate pathological phenotypes of TNBS induced CD-like colitis in mice. Our results provide a new hopeful therapeutic strategy in treating CD, especially for those who suffered from the tolerance of existing immunosuppressive agent drugs.
Asunto(s)
Colitis Ulcerosa/tratamiento farmacológico , Enfermedad de Crohn/tratamiento farmacológico , Ciclohexilaminas/farmacología , Ferroptosis/efectos de los fármacos , Inmunosupresores/farmacología , Fenilendiaminas/farmacología , Ácido Trinitrobencenosulfónico/antagonistas & inhibidores , Animales , Colitis Ulcerosa/inducido químicamente , Colitis Ulcerosa/patología , Enfermedad de Crohn/inducido químicamente , Enfermedad de Crohn/patología , Femenino , Humanos , Ratones , Ratones Endogámicos BALB CRESUMEN
Previously, we reported that 3, 4-oxo-isopropylidene-shikimic acid (ISA) has therapeutic potential in experimental colitis in rats. This study aimed to elucidate the potential mechanisms of ISA on the inflammatory response in rats with 2, 4, 6-trinitrobenzenesulfonic acid-induced colitis. After the induction of colitis, rats were orally administered ISA for 12 days. Then, the expression levels of inflammatory cytokines, cell adhesion molecules, and matrix metalloproteinase (MMP) in the blood and colon tissues, and the protein level of nuclear factor kappa B (NF-κB) p65 in cytoplasm and nucleus of colon tissues were evaluated. As a result, an enhanced inflammatory response was observed in rats with experimental colitis. However, the treatment with ISA significantly ameliorated the inflammatory response, which was manifested as a significant decrease in the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, interferon (IFN)-γ, IL-8, TNF-α mRNA, P-selectin, E-selectin, intercellular cell adhesion molecule-1, MMP9 and MMP9 mRNA in rat blood and colon tissues, respectively, and a significant decrease in the levels of IFN-γ/IL-4, and the NF-κBp65 activity coefficient. Therefore, the therapeutic effect of ISA on experimental colitis may be related to its inhibitory effect on the expression of cytokines, adhesion molecules, and MMP9, which may be involved in the inhibition of the activation and nuclear translocation of NF-κBp65.
Asunto(s)
Colitis/tratamiento farmacológico , Modelos Animales de Enfermedad , Ácido Shikímico/farmacología , Ácido Trinitrobencenosulfónico/antagonistas & inhibidores , Animales , Colitis/inducido químicamente , Colitis/inmunología , Citocinas/análisis , Citocinas/inmunología , Relación Dosis-Respuesta a Droga , Inflamación/inducido químicamente , Inflamación/tratamiento farmacológico , Masculino , Conformación Molecular , Ratas , Ratas Sprague-Dawley , Ácido Shikímico/análogos & derivados , Ácido Shikímico/químicaRESUMEN
The nuclear factor-κB (NF-κB)-mediated activation of macrophages plays a key role in mucosal immune responses in Crohn's disease (CD). Moreover, increasing evidence shows that the activation of peroxisome proliferator-activated receptor-γ (PPAR-γ) exerts satisfactory anti-inflammatory effects in experimental colitis models, mostly by suppressing NF-κB-mediated macrophage activation. Therefore, exploring therapeutic strategies to activate PPAR-γ and inhibit the NF-κB pathway in colonic macrophages holds great promise for the treatment of CD. In this study, five novel pyrazole-containing indolizine derivatives (B1, B2, B3, B4 and B5) were successfully synthesized and characterized, and their anti-inflammatory activities for CD treatment were also investigated. Among the five compounds, compound B4 effectively decreased the NF-κB-mediated production of the pro-inflammatory cytokine TNF-α in LPS-stimulated peritoneal macrophages. Moreover, compound B4 significantly ameliorated 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced mouse colitis symptoms, including body weight loss, colonic pathological damage and inflammatory cell infiltration. The results of western blotting and luciferase reporter assays indicated that compound B4 activated PPAR-γ and subsequently suppressed NF-κB activation. Conversely, the addition of the PPAR-γ antagonist GW9662 abrogated the anti-inflammatory effects of compound B4 both in vitro and in vivo. In summary, compound B4 activated the PPAR-γ pathway to inhibit downstream NF-κB signaling, which alleviated experimental colitis. Thus, this compound may serve as a potential therapeutic agent for patients with CD.
Asunto(s)
Colitis/metabolismo , Indolizinas/uso terapéutico , FN-kappa B/metabolismo , PPAR gamma/metabolismo , Pirazoles/uso terapéutico , Ácido Trinitrobencenosulfónico/toxicidad , Anilidas/farmacología , Animales , Colitis/inducido químicamente , Colitis/prevención & control , Femenino , Indolizinas/farmacología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos ICR , FN-kappa B/antagonistas & inhibidores , PPAR gamma/antagonistas & inhibidores , Sustancias Protectoras/farmacología , Sustancias Protectoras/uso terapéutico , Pirazoles/farmacología , Ácido Trinitrobencenosulfónico/antagonistas & inhibidoresRESUMEN
Lectins bind to surface receptors on target cells, and activate a cascade of events, eventually leading to altered immune status of host. The immunomodulatory potential of purified lectin from Aspergillus nidulans was evaluated in Swiss albino mice treated intraperitoneally with seven different doses of purified lectin. Lectin prevented BSA-induced Arthus reaction and systemic anaphylaxis. The enhanced functional ability of macrophages was evident from respiratory burst activity and nitric oxide production in splenocyte cultures. Interferon-gamma and interleukin-6 levels were significantly up-regulated in treated groups. Maximum stimulatory effect was observed at the dose of 1.5 mg/kg body weight. Therapeutic potential of A. nidulans lectin was assessed against trinitrobenzene sulfonic acid-induced ulcerative colitis in male Wistar rats. Rats pre-treated with 80 mg/kg body weight of purified lectin intraperitoneally prior to colitis induction showed lesser disease severity and recovery within 7 days, while rats post-treated with the same dose showed recovery in 11 days. The results demonstrate immunomodulatory effects of A. nidulans lectin in Swiss albino mice, resulting in improved immune status of the animals and unfold its curative effect against ulcerative colitis in rat model. This is the first report on immunomodulatory and therapeutic potential of a lectin from microfungi.
Asunto(s)
Anafilaxia/prevención & control , Reacción de Arthus/prevención & control , Aspergillus nidulans/química , Colitis Ulcerosa/tratamiento farmacológico , Proteínas Fúngicas , Factores Inmunológicos , Lectinas , Anafilaxia/inducido químicamente , Anafilaxia/tratamiento farmacológico , Anafilaxia/inmunología , Animales , Reacción de Arthus/inducido químicamente , Reacción de Arthus/tratamiento farmacológico , Reacción de Arthus/inmunología , Bovinos , Colitis Ulcerosa/inducido químicamente , Colitis Ulcerosa/inmunología , Colitis Ulcerosa/prevención & control , Modelos Animales de Enfermedad , Relación Dosis-Respuesta Inmunológica , Proteínas Fúngicas/farmacología , Proteínas Fúngicas/uso terapéutico , Factores Inmunológicos/farmacología , Factores Inmunológicos/uso terapéutico , Interferón gamma/biosíntesis , Interleucina-6/biosíntesis , Lectinas/farmacología , Lectinas/uso terapéutico , Macrófagos/citología , Macrófagos/efectos de los fármacos , Macrófagos/metabolismo , Masculino , Ratones , Micelio/química , Óxido Nítrico/biosíntesis , Ratas , Ratas Wistar , Albúmina Sérica/administración & dosificación , Albúmina Sérica/efectos adversos , Albúmina Sérica/antagonistas & inhibidores , Ácido Trinitrobencenosulfónico/administración & dosificación , Ácido Trinitrobencenosulfónico/efectos adversos , Ácido Trinitrobencenosulfónico/antagonistas & inhibidoresRESUMEN
OBJECTIVES: The aim of the present study was to investigate the time dependent changes in hemodynamic parameters and to assess the role of endothelin (ET) receptors in trinitrobenzene sulfonic acid (TNBS) induced colitis. MATERIALS: Inferior mesenteric artery (IMA) hemodynamics, myeloperoxidase activity (MPO) and damage scores were measured immediately or 1, 3, 5 and 14 days after colitis. TREATMENTS: Another group of rats received a nonselective ET receptor antagonist bosentan (30 mg/kg/day), ET-A receptor antagonist BQ485 (60 microg/rat/day) or ET-B receptor antagonist BQ788 (60 microg/rat/day) prior to and on the 1st, 2nd and 3rd days after TNBS administration. RESULTS: IMA flow significantly increased at 90 min followed by a substantial decrease through days 1-5. Tissue MPO activity and macroscopic damage score increased on 1st day after the induction of colitis and remained elevated 3, 5 and 14 days following colitis. Treatment with bosentan or ET-A receptor antagonist largely prevented the colitis-induced reduction in blood flow and tissue injury whereas ET-B receptor antagonist did not attenuate tissue injury or reductions in blood flow. CONCLUSIONS: Our results demonstrate that time-dependent abnormalities occur in IMA hemodynamics following TNBS administration. Our findings also indicate that ET-A receptors but not ET-B receptors play an important role in the colonic inflammation following TNBS administration.
Asunto(s)
Colitis/inducido químicamente , Arterias Mesentéricas/efectos de los fármacos , Arterias Mesentéricas/patología , Peroxidasa/metabolismo , Receptores de Endotelina/fisiología , Flujo Sanguíneo Regional/efectos de los fármacos , Ácido Trinitrobencenosulfónico/antagonistas & inhibidores , Animales , Antihipertensivos/farmacología , Azepinas/farmacología , Bosentán , Colitis/patología , Inflamación/tratamiento farmacológico , Masculino , Membrana Mucosa/patología , Oligopéptidos/farmacología , Ratas , Ratas Sprague-Dawley , Sulfonamidas/farmacología , Factores de TiempoRESUMEN
NCX-1015 is a nitric oxide (NO)-releasing derivative of prednisolone. In this study we show NCX-1015 protects mice against the S. A. development and induces healing of T helper cell type 1-mediated experimental colitis induced by intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS). The beneficial effect of NCX-1015 was reflected in increased survival rates, improvement of macroscopic and histologic scores, a decrease in the mucosal content of T helper cell type 1 cytokines (protein and mRNA), and diminished myeloperoxidase activity in the colon. In contrast to its NO derivative, only very high doses of prednisolone were effective in reproducing these beneficial effects. NCX-1015 was 10- to 20-fold more potent than the parent compound in inhibiting IFN-gamma secretion by lamina propria mononuclear cells. Protection against developing colitis correlated with inhibition of nuclear translocation of p65Rel A in these cells. In vivo treatment with NCX-1015 potently stimulated IL-10 production, suggesting that the NO steroid induces a regulatory subset of T cells that negatively modulates intestinal inflammation.
Asunto(s)
Antiinflamatorios/farmacología , Colitis/prevención & control , Mucosa Intestinal/efectos de los fármacos , Prednisolona/análogos & derivados , Prednisolona/farmacología , Subgrupos de Linfocitos T/efectos de los fármacos , Ácido Trinitrobencenosulfónico/antagonistas & inhibidores , Transporte Activo de Núcleo Celular/efectos de los fármacos , Animales , Colitis/inducido químicamente , Colitis/tratamiento farmacológico , Colitis/patología , Evaluación Preclínica de Medicamentos , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/patología , Interferón gamma/biosíntesis , Interleucina-10/biosíntesis , Mucosa Intestinal/patología , Linfocinas/biosíntesis , Masculino , Mesenterio/irrigación sanguínea , Ratones , Ratones Endogámicos BALB C , Modelos Animales , FN-kappa B/metabolismo , Neutrófilos/enzimología , Peroxidasa/análisis , Subgrupos de Linfocitos T/inmunología , Factor de Transcripción ReIA , Ácido Trinitrobencenosulfónico/toxicidadRESUMEN
In human, digestive disorders are often associated with visceral pain. In these pathologies, visceral pain threshold is decreased indicating a visceral hypersensitivity. Pregabalin [CI-1008; S-(+)-3-isobutylgaba] presents antihyperalgesic actions in inflammatory somatic pain models. This study was designed to evaluate 1) the effect of injection of TNBS into the colon on visceral pain threshold, and 2) the antihyperalgesic effect of pregabalin on TNBS-induced chronic colonic allodynia. A significant decrease in the colonic pain threshold was observed in trinitrobenzene sulfonic acid (TNBS)-treated animals (17.8 +/- 1.27 versus 43.4 +/- 1.98 mm Hg). Pregabalin (30-200 mg/kg s.c.) and morphine (0.1-1 mg/kg s.c.) showed a dose-related inhibition of TNBS-induced colonic allodynia. Pregabalin did not inhibit the colonic inflammatory effect of TNBS. In normal conditions (control animals), morphine (0.3 mg/kg s.c.) significantly increased the colonic pain threshold, whereas pregabalin (200 mg/kg s.c.) did not modify the colonic pain threshold. Pregabalin suppressed the TNBS-induced colonic allodynia but did not modify the colonic threshold in normal conditions. The ability of pregabalin to block the chronic colonic allodynia indicates that it is effective in abnormal colonic hypersensitivity, suggesting a possible effect in chronic pain in irritable bowel syndrome.
Asunto(s)
Enfermedades del Colon/tratamiento farmacológico , Dolor/tratamiento farmacológico , Ácido Trinitrobencenosulfónico/antagonistas & inhibidores , Ácido gamma-Aminobutírico/análogos & derivados , Ácido gamma-Aminobutírico/uso terapéutico , Analgésicos Opioides/uso terapéutico , Animales , Enfermedad Crónica , Colon/patología , Enfermedades del Colon/inducido químicamente , Enfermedades del Colon/complicaciones , Hiperemia/inducido químicamente , Hiperemia/patología , Masculino , Morfina/uso terapéutico , Tamaño de los Órganos/efectos de los fármacos , Dolor/etiología , Peroxidasa/metabolismo , Pregabalina , Ratas , Ratas Sprague-Dawley , Factores de Tiempo , Ácido Trinitrobencenosulfónico/toxicidadRESUMEN
Trinitrobenzene sulfonic acid (TNBS)-induced colitis is an IL-12-driven, Th1 T cell-mediated colitis that resembles human Crohn's disease. In the present study, we showed initially that the oral administration of recombinant subunit B of cholera toxin (rCT-B) at the time of TNBS-induced colitis by intrarectal TNBS instillation inhibits the development of colitis or, at later time when TNBS-induced colitis is well established, brings about resolution of the colitis. Dose-response studies showed that a majority of mice (68%) treated with rCT-B at a dose of 100 microg (times four daily doses) exhibited complete inhibition of the development of colitis, whereas a minority (30%) treated with rCT-B at a dose of 10 microg (times four daily doses) exhibited complete inhibition; in both cases, however, the remaining mice exhibited some reduction in the severity of inflammation. In further studies, we showed that rCT-B administration is accompanied by prevention/reversal of increased IFN-gamma secretion (the hallmark of a Th1 response) without at the same time causing an increase in IL-4 secretion. This decreased IFN-gamma secretion was not associated with the up-regulation of the secretion of counterregulatory cytokines (IL-10 or TGF-beta), but was associated with a marked inhibition of IL-12 secretion, i.e., the secretion of the cytokine driving the Th1 response. Finally, we showed that rCT-B administration results in increased apoptosis of lamina propria cells, an effect previously shown to be indicative of IL-12 deprivation. From these studies, rCT-B emerges as a powerful inhibitor of Th1 T cell-driven inflammation that can conceivably be applied to the treatment of Crohn's disease.
Asunto(s)
Toxina del Cólera/administración & dosificación , Toxina del Cólera/inmunología , Colitis/inmunología , Colitis/prevención & control , Interleucina-12/antagonistas & inhibidores , Interleucina-12/fisiología , Ácido Trinitrobencenosulfónico , Administración Oral , Administración Rectal , Animales , Apoptosis/inmunología , Células Cultivadas , Colitis/inducido químicamente , Colitis/patología , Colon/inmunología , Colon/metabolismo , Colon/patología , Progresión de la Enfermedad , Interferón gamma/biosíntesis , Interleucina-10/biosíntesis , Interleucina-12/biosíntesis , Interleucina-4/biosíntesis , Mucosa Intestinal/inmunología , Mucosa Intestinal/metabolismo , Mucosa Intestinal/patología , Leucocitos Mononucleares/inmunología , Leucocitos Mononucleares/metabolismo , Masculino , Ratones , Ratones Endogámicos , Oxazolona/administración & dosificación , Proteínas Recombinantes/administración & dosificación , Proteínas Recombinantes/inmunología , Factor de Crecimiento Transformador beta/biosíntesis , Ácido Trinitrobencenosulfónico/administración & dosificación , Ácido Trinitrobencenosulfónico/antagonistas & inhibidoresRESUMEN
The effect of BPC-15 (Booly Protection Compound-15) was evaluated in a rat model of colonic injury. A single intracolonic administration of trinitrobenzene sulfonic acid (TNBS) dissolved in ethanol induces severe colonic damage, which is characterized by areas of necrosis surrounded by areas of acute inflammation. The damage is associated with high myeloperoxidase (MPO) activity, mainly as a reflection of neutrophilic infiltration into the damaged tissue. In this study, 1 hr before a single intracolonic administration of 50 mg/kg of TNBS in 50% ethanol, the animals were treated with one of the following doses of BPC-15: 0.0001, 0.001, 0.01, 0.1, 1 or 10 nmol/kg administered i.p. or with a dose of 10 nmol/kg administered intracolonically. The animals were sacrificed 3 days later and the extent of colonic necrosis and hyperemia was measured with an image analyzer. The i.p. administration of BPC-15 significantly reduced the extent of TNBS-induced colonic damage in a dose-dependent manner. This was associated with a statistically significant and dose-dependent reduction in colonic tissue MPO activity. At the dose tested (10 nmol/kg), intracolonic administration of BPC-15 did not significantly reduce either the extent of the colonic damage or the increase in MPO activity induced by TNBS. In conclusion, this study showed that i.p. administration of BPC-15 reduced TNBS-induced colonic damage in rats.
Asunto(s)
Colitis/inducido químicamente , Fragmentos de Péptidos/farmacología , Proteínas/farmacología , Ácido Trinitrobencenosulfónico/antagonistas & inhibidores , Secuencia de Aminoácidos , Animales , Masculino , Datos de Secuencia Molecular , Peroxidasa/metabolismo , Ratas , Ratas Sprague-Dawley , Ácido Trinitrobencenosulfónico/toxicidadRESUMEN
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.
Asunto(s)
Capsaicina/farmacología , Colitis/prevención & control , Ácido Trinitrobencenosulfónico/antagonistas & inhibidores , Administración Tópica , Animales , Capsaicina/administración & dosificación , Capsaicina/análogos & derivados , Capsaicina/farmacocinética , Colitis/inducido químicamente , Diterpenos/farmacocinética , Técnicas In Vitro , Cinética , Masculino , Membranas/efectos de los fármacos , Membranas/metabolismo , Ratas , Ratas Sprague-Dawley , Receptores de Droga/efectos de los fármacos , Ácido Trinitrobencenosulfónico/farmacologíaRESUMEN
The effects of colonic inflammation induced by trinitrobenzene sulfonic acid and influence of previous treatment with specific antagonists of inflammatory mediators (platelet-activating factor, leukotrienes, prostaglandins, and thromboxanes) on colonic transit were examined in conscious rats which were permanently fitted with an intracolonic catheter inserted into the proximal colon. Colonic inflammation was induced by intracolonic administration of trinitrobenzene acid (80 mg/kg) in 50% ethanol. Colonic transit time was evaluated by intracolonic administration of a radiolabeled marker [( 51Cr]sodium chromate) and collection of the feces per hour on a conveyor belt. Excretion of the marker was then plotted vs. time, permitting calculations of the times elapsed to recover 25%, 50%, and 75% of the marker injected (T25, T50, and T75, respectively). In control (saline) animals, excretion of the marker described a regular sigmoid curve with 50% of the marker recovered at 6.92 +/- 0.40 hours after intracolonic administration (T25 = 6.4 +/- 0.43 hours; T75 = 7.49 +/- 0.39 hours). Ethanol (vehicle), 50%, did not modify the profile of marker recovery. On the contrary, single intracolonic administration of trinitrobenzene sulfonic acid/ethanol induced a biphasic response consisting of an early pool of radiolabeled feces (T25 = 4.03 +/- 0.55 hours) with a delayed total one (T50 = 11.74 +/- 0.83 hours; T75 = 13.70 +/- 0.49 hours). Antagonists of the leukotriene pathway, i.e., MK = 886, a lipoxygenase inhibitor, and SKF 104,353 and SR 2640, two different leukotriene D4 receptor antagonists, blocked the effects of trinitrobenzene sulfonic acid on colonic transit time and restored a control profile of radiolabeled marker excretion. In contrast, indomethacin, a cyclooxygenase inhibitor, and SC 19220, a specific prostaglandin E2 receptor antagonist, were inefficient in blocking the effects of trinitrobenzene sulfonic acid on colonic transit time. Specific thromboxane A2 receptor antagonists, KT1-32 and GR 32191B, did not show any improvement in colonic transit after trinitrobenzene sulfonic acid administration. Previous injection of the specific platelet-activating factor receptor antagonists, BN 52021 or BN 50730, was also unable to restore a normal marker excretion profile after administration of trinitrobenzene sulfonic acid. It is concluded that the alterations of colonic transit immediately observed after intracolonic trinitrobenzene sulfonic acid administration are mediated through the release of leukotriene D4. In contrast, platelet-activating factor, prostaglandins, and thromboxanes are not involved in the mediation of these transit disturbances.
Asunto(s)
Colon/fisiopatología , Tránsito Gastrointestinal/efectos de los fármacos , SRS-A/fisiología , Ácido Trinitrobencenosulfónico/administración & dosificación , Animales , Masculino , Factor de Activación Plaquetaria/farmacología , Ratas , Ratas Endogámicas , Valores de Referencia , Ácido Trinitrobencenosulfónico/antagonistas & inhibidores , Ácido Trinitrobencenosulfónico/farmacologíaRESUMEN
Bisphosphoglyceromutase and 2,3-bisphosphoglycerate phosphatase activities responsible for 2,3-bisphosphoglycerate metabolsim in human red cells are displayed by the same enzyme protein which has phosphoglyceromutase activity [Sasaki, R., et al. (1975) Eur J. Biochem. 50, 581-593]. This enzyme was subjected to chemical modification by trinitrobenzenesulfonate. The three enzyme activities were inactivated by trinitrobenzenesulfonate at the same rate. The sulfhydryl content of the enzyme was unchanged during trinitrophenylation, indicating that derivatization was through the amino group. Trinitrophenylation of about one amino group per mole of the enzyme resulted in complete loss of the three activities. Both 2,3-bisphosphoglycerate and 1,3-bisphosphoglycerate inhibited trinitrophenylation and effectively protected the enzyme from inactivation. Although monophosphoglycerates did not show any protective effect at concentrations which should be adequate based upon their kinetic constants, they were protective at higher concentrations. Inactivation by trinitrophenylation was an apparent first-order reaction. The dissociation constant of the enzyme - 2,3-bisphosphoglycerate complex was determined by analyzing the first-order reaction on the assumption that the protective effect of 2,3-bisphosphoglycerate was due to competition with trinitrobenzenesulfonate. The dissociation constant was in good agreement with kinetic constants of 2,3-bisphosphoglycerate in the enzyme reactions, which indicated that 2,3-bisphosphoglycerate did indeed exert its protective effect through competition with trinitrobenzenesulfonate for an amino group of the enzyme. The protective effect of monophosphoglycerates could be rationalized with kinetic evidence that 2-phosphoglycerate at high concentrations interacts with the 2,3-bisphosphoglycerate binding site. These results indicate that the enzyme exhibits the three enzyme activities at a common active site at which one amino group essential for binding of bisphosphoglycerates is located. Based on the multifunctional properties of this enzyme, a possible mechanism was discussed for regulation of 2,3-bisphosphoglycerate metabolism in human red cells.