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Rubinstein MR, Burgueño AL, Quiroga S, Wald MR, Genaro AM. Current Understanding of the Roles of Gut-Brain Axis in the Cognitive Deficits Caused by Perinatal Stress Exposure. Cells 2023; 12:1735. [PMID: 37443769 PMCID: PMC10340286 DOI: 10.3390/cells12131735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 06/15/2023] [Accepted: 06/19/2023] [Indexed: 07/15/2023] Open
Abstract
The term 'perinatal environment' refers to the period surrounding birth, which plays a crucial role in brain development. It has been suggested that dynamic communication between the neuro-immune system and gut microbiota is essential in maintaining adequate brain function. This interaction depends on the mother's status during pregnancy and/or the newborn environment. Here, we show experimental and clinical evidence that indicates that the perinatal period is a critical window in which stress-induced immune activation and altered microbiota compositions produce lasting behavioral consequences, although a clear causative relationship has not yet been established. In addition, we discuss potential early treatments for preventing the deleterious effect of perinatal stress exposure. In this sense, early environmental enrichment exposure (including exercise) and melatonin use in the perinatal period could be valuable in improving the negative consequences of early adversities. The evidence presented in this review encourages the realization of studies investigating the beneficial role of melatonin administration and environmental enrichment exposure in mitigating cognitive alteration in offspring under perinatal stress exposure. On the other hand, direct evidence of microbiota restoration as the main mechanism behind the beneficial effects of this treatment has not been fully demonstrated and should be explored in future studies.
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Affiliation(s)
- Mara Roxana Rubinstein
- Laboratorio de Psiconeuroendocrinoinmunologia, Instituto de Investigaciones Biomédicas, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)—Pontificia Universidad Católica Argentina, Buenos Aires C1107AFF, Argentina; (A.L.B.); (S.Q.); (M.R.W.)
| | | | | | | | - Ana María Genaro
- Laboratorio de Psiconeuroendocrinoinmunologia, Instituto de Investigaciones Biomédicas, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)—Pontificia Universidad Católica Argentina, Buenos Aires C1107AFF, Argentina; (A.L.B.); (S.Q.); (M.R.W.)
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Palumbo ML, Prochnik A, Wald MR, Genaro AM. Chronic Stress and Glucocorticoid Receptor Resistance in Asthma. Clin Ther 2020; 42:993-1006. [PMID: 32224031 DOI: 10.1016/j.clinthera.2020.03.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/04/2020] [Accepted: 03/04/2020] [Indexed: 12/14/2022]
Abstract
PURPOSE Chronic and persistent exposure to negative stress can lead to adverse consequences on health. Particularly, psychosocial factors were found to increase the risk and outcome of respiratory diseases like asthma. Glucocorticoids (GCs) are the most efficient anti-inflammatory therapy for asthma. However, a significant proportion of patients don't respond adequately to GC administration. GC sensitivity is modulated by genetic and acquired disease-related factors. Additionally, it was proposed that endogenous corticosteroids may limit certain actions of synthetic GCs, contributing to insensitivity. Psychological and physiological stresses activate the hypothalamic-pituitary-adrenal axis, increasing cortisol levels. Here, we review the mechanism involved in altered GC sensitivity in asthmatic patients under stressful situations. Strategies for modulation GC sensitivity and improving GC therapy are discussed. METHODS PubMed was searched for publications on psychological chronic stress and asthma, GC resistance in asthma, biological mechanisms for GC resistance, and drugs for steroid-resistant asthma, including highly potent GCs. FINDINGS GC resistance in patients with severe disease remains a major clinical problem. In asthma, experimental and clinical evidence suggests that chronic stress induces inflammatory changes, contributing to a worse GC response. GC resistant patients can be treated with other broad-spectrum anti-inflammatory drugs, but these generally have major side effects. Different mechanisms of GC resistance have been described and might be useful for developing new therapeutic strategies against it. Novel drugs, such as highly potent GCs, phosphoinositide 3-kinase-delta inhibitors that reestablish histone deacetylase-2 function, decrease of GC receptor phosphorylation by p38 mitogen-activated protein kinase inhibitors, or phosphatase activators, are currently in clinical development and might be combined with GC therapy in the future. Furthermore, microRNAs (small noncoding RNA molecules) operate as posttranscriptional regulators, providing another level of control of GC receptor levels. Empirical results allow postulating that the detection and study of microRNAs might be a promising approach to better characterize and treat asthmatic patients. IMPLICATIONS Many molecular and cellular pathobiological mechanisms are responsible of GC resistance. Therefore detecting specific biomarkers to help identify patients who would benefit from new therapies is crucial. Stress consitutes a negative aspect of current lifestyles that increase asthma morbidity and mortality. Adequate stress management could be an important and positive intervention.
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Affiliation(s)
- María Laura Palumbo
- Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires (UNNOBA-UNSADA-CONICET), Junín, Argentina
| | - Andrés Prochnik
- Instituto de Investigaciones Biomédicas (UCA-CONICET), Buenos Aires, Argentina
| | - Miriam Ruth Wald
- Instituto de Investigaciones Biomédicas (UCA-CONICET), Buenos Aires, Argentina
| | - Ana María Genaro
- Instituto de Investigaciones Biomédicas (UCA-CONICET), Buenos Aires, Argentina; Departamento de Farmacología, Facultad de Medicina, UBA Paraguay, Buenos Aires, Argentina.
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Pascuan CG, Di Rosso ME, Pivoz-Avedikian JE, Wald MR, Zorrilla Zubilete MA, Genaro AM. Alteration of neurotrophin and cytokine expression in lymphocytes as novel peripheral markers of spatial memory deficits induced by prenatal stress. Physiol Behav 2017; 173:144-155. [DOI: 10.1016/j.physbeh.2017.01.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 01/30/2017] [Accepted: 01/31/2017] [Indexed: 12/31/2022]
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Inzaugarat ME, De Matteo E, Baz P, Lucero D, García CC, Gonzalez Ballerga E, Daruich J, Sorda JA, Wald MR, Cherñavsky AC. New evidence for the therapeutic potential of curcumin to treat nonalcoholic fatty liver disease in humans. PLoS One 2017; 12:e0172900. [PMID: 28257515 PMCID: PMC5336246 DOI: 10.1371/journal.pone.0172900] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/10/2017] [Indexed: 02/06/2023] Open
Abstract
Introduction The immune system acts on different metabolic tissues that are implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Leptin and linoleic acid have the ability to potentially affect immune cells, whereas curcumin is a known natural polyphenol with antioxidant and anti-inflammatory properties. Aims This study was designed to evaluate the pro-inflammatory and pro-oxidant effects of leptin and linoleic acid on immune cells from patients with NAFLD and to corroborate the modulatory effects of curcumin and its preventive properties against the progression of NAFLD using a high-fat diet (HFD)-induced NAFLD/nonalcoholic steatohepatitis mouse model. Results The ex vivo experiments showed that linoleic acid increased the production of reactive oxygen species in monocytes and liver macrophages, whereas leptin enhanced tumor necrosis factor-α (TNF-α) production in monocytes and interferon-γ production in circulating CD4+ cells. Conversely, oral administration of curcumin prevented HFD-induced liver injury, metabolic alterations, intrahepatic CD4+ cell accumulation and the linoleic acid- and leptin- induced pro-inflammatory and pro-oxidant effects on mouse liver macrophages. Conclusion Our findings provide new evidence for the therapeutic potential of curcumin to treat human NAFLD. However, the development of a preventive treatment targeting human circulating monocytes and liver macrophages as well as peripheral and hepatic CD4+ cells requires additional research.
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Affiliation(s)
- María Eugenia Inzaugarat
- Instituto de Inmunología, Genética y Metabolismo-CONICET- Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Elena De Matteo
- Hospital de Niños “Dr. R. Gutiérrez”, Servicio de Patología, Buenos Aires, Argentina
| | - Placida Baz
- Instituto de Inmunología, Genética y Metabolismo-CONICET- Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Diego Lucero
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica - Departamento de Bioquímica Clínica, Laboratorio de Lípidos y Arterioesclerosis, Buenos Aires, Argentina
| | - Cecilia Claudia García
- Instituto de Inmunología, Genética y Metabolismo-CONICET- Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Esteban Gonzalez Ballerga
- Universidad de Buenos Aires, Hospital de Clínicas "José de San Martin"- División de Gastroenterología, Buenos Aires, Argentina
| | - Jorge Daruich
- Universidad de Buenos Aires, Hospital de Clínicas "José de San Martin"- División de Gastroenterología, Buenos Aires, Argentina
| | - Juan Antonio Sorda
- Universidad de Buenos Aires, Hospital de Clínicas "José de San Martin"- División de Gastroenterología, Buenos Aires, Argentina
| | - Miriam Ruth Wald
- Instituto de Investigaciones Biomédicas (BIOMED)- Universidad católica Argentina-Consejo Nacional de Investigaciones Científicas y Tecnológicas, Buenos Aires, Argentina
| | - Alejandra Claudia Cherñavsky
- Instituto de Inmunología, Genética y Metabolismo-CONICET- Universidad de Buenos Aires, Buenos Aires, Argentina
- * E-mail:
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Lipszyc PS, Cremaschi GA, Zorrilla-Zubilete M, Bertolino MLA, Capani F, Genaro AM, Wald MR. Niacin Modulates Pro-inflammatory Cytokine Secretion. A Potential Mechanism Involved in its Anti-atherosclerotic Effect. Open Cardiovasc Med J 2013; 7:90-8. [PMID: 24155799 PMCID: PMC3805984 DOI: 10.2174/1874192401307010090] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/18/2013] [Accepted: 05/20/2013] [Indexed: 12/12/2022] Open
Abstract
The pathogenesis of atherosclerosis includes the assignment of a critical role to cells of the monocyte/macrophage lineage and to pro-inflammatory cytokines. Niacin is known to improve lipid metabolism and to produce beneficial modification of cardiovascular risk factors. The aim of this work was to investigate if Niacin is able to modulate pro-inflammatory cytokine production in macrophages in a murine model of atherosclerosis. For this purpose C57Bl/6J mice fed with atherogenic diet (AGD) or with conventional chow diet were used. The AGD group showed an increase in body weight and in total plasma cholesterol, with no differences in triglyceride or HDL levels. Lesions in arterial walls were observed. The characterization of Niacin receptor showed an increase in the receptor number of macrophages from the AGD group. Macrophages from control and AGD animals treated in vitro with an inflammatory stimulus showed elevated levels of IL-6, IL-1 and TNF-α, that were even higher in macrophages from AGD mice. Niacin was able to decrease the production of pro-inflammatory cytokines in stimulated macrophages. Similar effect of Niacin was observed in an in vivo model of inflammation. These results show an attenuating inflammatory mechanism for this therapeutic agent and would point out its potential action in plaque stabilization and in the prevention of atherosclerosis progression. Furthermore, the present results provide the basis for future studies on the potential contribution of Niacin to anti-inflammatory therapies.
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Affiliation(s)
- Pedro Saul Lipszyc
- Primera Cátedra de Farmacología, Departamento de Farmacología Facultad de Medicina, Universidad de Buenos Aires (UBA), Argentina
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Rubinstein MR, Genaro AM, Wald MR. Differential effect of hyperglycaemia on the immune response in an experimental model of diabetes in BALB/cByJ and C57Bl/6J mice: participation of oxidative stress. Clin Exp Immunol 2013; 171:319-29. [PMID: 23379439 DOI: 10.1111/cei.12020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/22/2012] [Indexed: 01/13/2023] Open
Abstract
Diabetes is associated with an increased risk of death from infectious disease. Hyperglycaemia has been identified as the main factor contributing to the development of diseases associated with diabetes mellitus. However, experimental evidence indicates individual susceptibility to develop complications of diabetes. In this context, the aim of this work was to study the immune response in a streptozotocin-induced type 1 diabetes in two mouse strains: BALB/cByJ and C57Bl/6J. The participation of hyperglycaemia and oxidative stress was also analysed. Diabetic BALB/cByJ mice showed a decrease in both the in-vivo and in-vitro immune responses, whereas diabetic C57Bl/6J mice had higher blood glucose but exhibited no impairment of the immune response. The influence of hyperglycaemia over the immune response was evaluated by preincubation of lymphocytes from normal mice in a high glucose-containing medium. T and B cells from BALB/cByJ mice showed a decrease in cell viability and mitogen-stimulated proliferation and an increase in apoptosis induction. An increase in oxidative stress was implicated in this deleterious effect. These parameters were not affected in the T and B lymphocytes from C57Bl/6J mice. In conclusion, BALB/cByJ mice were sensitive to the deleterious effect of hyperglycaemia, while C57BL/6J were resistant. Although an extrapolation of these results to clinical conditions must be handled with caution, these results highlight the need to contemplate the genetic background to establish models to study the deleterious effect of diabetes in order to understand phenotypical variations that are of clinical importance in the treatment of patients.
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Affiliation(s)
- M R Rubinstein
- Centro de Estudios Farmacológicos y Botánicos, Consejo Nacional de Investigaciones Científicas y Técnicas, Primera Cátedra de Farmacología, Universidad de Buenos Aires, Buenos Aires, Argentina
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Rubinstein MR, Cremaschi GA, Oliveri LM, Gerez EN, Wald MR, Genaro AM. Possible involvement of stress hormones and hyperglycaemia in chronic mild stress-induced impairment of immune functions in diabetic mice. Stress 2010; 13:384-91. [PMID: 20666647 DOI: 10.3109/10253891003667888] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Stress, an important aspect of modern life, has long been associated with an altered homeostatic state. Little is known about the effect of the life stress on the outcome of diabetes mellitus, especially related to the higher risk of infections. Here, we evaluate the effects of chronic mild stress (CMS) exposure on the evolution of type I diabetes induced by streptozotocin administration in BALB/c mice. Exposure of diabetic mice to CMS resulted in a significant reduction of survival and a sustained increase in blood glucose values. Concerning the immune response, chronic stress had a differential effect in mice with diabetes with respect to controls, showing a marked decrease in both T- and B-cell proliferation. No correlation was found between splenic catecholamine or circulating corticosterone levels and the proliferative response. However, a significant negative correlation was found between glucose levels and concanavalin A- and lipopolysaccharide-stimulated proliferative responses of T and B cells. A positive correlation between blood glucose and splenic catecholamine concentrations was found in diabetic mice but not in controls subjected to CMS. Hence, the present report shows that diabetic mice show a worse performance in immune function after stress exposure, pointing to the importance of considering life stress as a risk factor for patients with diabetes.
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Affiliation(s)
- M R Rubinstein
- Facultad de Medicina, Centro de Estudios Farmacológicos y Botánicos (CEFYBO), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 1era Cátedra de Farmacología, Universidad de Buenos Aires, Paraguay 2155, Piso 15, 1121 Buenos Aires, Argentina
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Rubinstein R, Genaro AM, Motta A, Cremaschi G, Wald MR. Impaired immune responses in streptozotocin-induced type I diabetes in mice. Involvement of high glucose. Clin Exp Immunol 2008; 154:235-46. [PMID: 18778365 DOI: 10.1111/j.1365-2249.2008.03742.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Diabetes is widely believed to predispose to serious infections. However, the mechanisms linking diabetes and immunosuppression are not well defined. One potential mediator of the altered defence mechanisms is hyperglycaemia. It has been identified as the main factor contributing to the development of diseases associated with diabetes mellitus. In this study we analyse the immune response in diabetes and the direct effect of hyperglycaemia on T and B lymphocyte reactivity. Diabetes induced an early decrease in IgG levels in the secondary response. However, both primary responses against a T-cell-dependent or independent antigen were affected after 6 months of diabetes induction. T- and B- cell proliferation was only decreased at this time. To gain insight into the potential mechanisms involved, we evaluated the influence of hyperglycaemia over the immune response. Pre-incubation of lymph node and spleen cells in a high glucose (HG) containing medium led to a significant time- and dose-dependent decrease in T- and B-cell proliferation. This effect was associated with the presence of HG-derived supernatants. Still viable cells after HG exposition were able to improve their proliferative response when cultured with the mitogen in a fresh standard medium. HG diminished cell viability, increased apoptosis and induced oxidative stress in lymphocytes. These results indicate that HG concentrations can directly affect lymphoid cell growth. An increase in oxidative stress would be implicated in this deleterious effect. The possibility that prolonged exposure to pathologically HG concentrations would result in the immunosuppressive state observed in diabetes is also discussed.
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Affiliation(s)
- R Rubinstein
- Laboratorio de Inmunofarmacología, Centro de Estudios Garmacológicos y Botánicos - Consejo Nacional de Investigaciones Científicas y Ténicas - Universidad de Buenos Aires, Facultad de Medicina, Buenos Aires, Argentina
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Abstract
The aim of the present study was to assess the effect of dehydroepiandrosterone (DHEA: 10 microM) and metformin (10 microM and 100 microM) in regulating proliferation of cultured T lymphocytes. T cells were isolated from lymph nodes of prepuberal BALB/c mice. We found that DHEA, metformin and DHEA + metformin added to the incubation media diminished proliferation of T cells. The inhibition by DHEA was higher than that produced by metformin, while the combined treatment showed a synergistic action that allowed us to speculate distinct regulatory pathways. This was supported later by other findings in which the addition of DHEA to the incubation media did not modify T lymphocyte viability, while treatment with metformin and DHEA + metformin diminished cellular viability and increased both early and late apoptosis. Moreover, DHEA diminished the content of the anti-oxidant molecule glutathione (GSH), whereas M and DHEA + metformin increased GSH levels and diminished lipid peroxidation. We conclude that DHEA and metformin diminish proliferation of T cells through different pathways and that not only the increase, but also the decrease of oxidative stress inhibited proliferation of T cells, i.e. a minimal status of oxidative stress, is necessary to trigger cellular response.
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Affiliation(s)
- M E Solano
- Laboratorio de Fisiopatología Ovárica, Centro de Estudios Farmacológicos y Botánicos, Universidad de Buenos Aires, Paraquay, Argentina
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Wald MR, Borda ES, Sterin-Borda L. Participation of nitric oxide and cyclic GMP in the supersensitivity of acute diabetic rat myocardium by cholinergic stimuli. Biochem Pharmacol 1998; 55:1991-9. [PMID: 9714319 DOI: 10.1016/s0006-2952(98)00069-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The purpose of this study was to explore the pharmacological and biochemical mechanisms involved in diabetic cardiomyopathy, with particular interest in the abnormal function of cholinergic neurotransmission at the onset of the pathology. The muscarinic acethylcholine agonist carbachol showed a negative inotropic response on both normal and diabetic isolated atria, but the latter showed a supersensitive response. No changes were found in muscarinic acethylcholine receptor (mAChR) expression. Measurements of mAChR-associated second messengers indicated no significant differences between normal and diabetic rat atria in the stimulatory effect of carbachol on protein kinase C activity and the production of inositol phosphates, or in the inhibitory effect induced by carbachol on cyclic AMP (cAMP) production. On the contrary, nitric oxide (NO) synthase activity and cyclic GMP production were higher in diabetic cardiac preparations than in normal ones. Moreover, in diabetic atria, nitric oxide synthase and guanylate cyclase inhibitors shifted the carbachol concentration-response curve on contractility to the right, reaching values similar to those of normal atria. These results suggest an early alteration in the mACh system during the diabetic state, associated with increased production of nitric oxide and cyclic GMP (cGMP). This, in turn, could increase the biological mechanical activity of the mAChR agonist, inducing in this way a higher pharmacological response, without changes in mAChR expression.
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Affiliation(s)
- M R Wald
- Centro de Estudios Farmacologicos y Botanicos, Consejo Nacional de Investigacion Cientificas y Tecnicas, Catedra de Farmacologia de la Facultad de Medicina y Odontologia de la Universidad de Buenos Aires, Argentina
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Abstract
The mitogenic effect of recombinant human erythropoietin (rHuEpo) on primary cultures of neonatal rat cardiac myocytes was observed. rHuEpo triggered a dose-dependent increase in myocyte proliferation. The hormone effect over optimally grown control culture 1 day after addition was maximum with 0.5 U/ml and was inhibited with anti-rHuEpo. Inhibitors of enzymatic pathways known to be involved in the cytokines intracellular mechanism such as genistein (tyrosine kinase inhibitor), 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate (phospholipase C [PLC] inhibitor), and 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (protein kinase C [PKC] inhibitor) prevented the mitogenic action of rHuEpo. Also the inhibition of Na(+)-K(+)-ATPase activity by ouabain blunted the stimulatory action of rHuEpo on cell proliferation. The mitogenic action of the hormone was correlated with cardiac membrane paranitrophenylphosphatase (pNPPase) and PKC activity, since concentrations of rHuEpo that stimulate DNA synthesis increased pNPPase and PKC activity. Moreover, the enzymatic inhibition of tyrosine kinase, PLC, and PKC attenuated the stimulatory action of rHuEpo upon cardiac pNPPase activity. In this paper we demonstrate a non-hematopoietic action of rHuEpo showing both mitogenic and enzymatic effect upon primary myocyte cell culture and on pNPPase activity of neonatal rat heart. These effects are related to the capacity of rHuEpo to stimulate Na(+)-K(+)-ATPase activity and appear to be secondary to the activation of tyrosine kinase and PKC, indicating that in the rHuEpo mediated mitogenic action on cardiomyocytes involves the activation of the same enzymatic pathways that have been described by other cytokines in different tissues.
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Affiliation(s)
- M R Wald
- Centro de Estudios Farmacologicos y Botanicos (CEFYBO), Facultad de Medicina y Odontologia de la Universidad de Buenos Aires, Argentina
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Abstract
Trypsin and alpha-chymotrypsin effects on masked insulin receptors were studied. Phospholipase C treatment, incubation in a high ionic strength buffer or solubilization were used as alternative procedures for the unmasking of insulin receptors. These three methods expose receptor structures which are inaccessible to insulin in the current experimental conditions of binding assays without any significant change in binding affinity. Both exposed and masked receptors proved to be equally sensitive to trypsin and alpha-chymotrypsin degradation. At 25 degrees C, about 5 micrograms trypsin/ml for 50 min or 80 micrograms alpha-chymotrypsin/ml for 200 min were necessary in each case to cause a 50% inhibition of the binding of 125I-iodo insulin to microsomes. The results suggest that masked receptors are only nonfunctional to bind insulin but they are not located in compartments inaccessible to molecules present in the medium.
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Affiliation(s)
- G E Scacchi
- Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Facultad de Farmacia y Bioquímica, Argentina
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