Hormones in the nucleus. Immunologically demonstrable biogenic amines (serotonin, histamine) in the nucleus of rat peritoneal mast cells Gyo ¨rgy Csaba a, * , Pe ´ter Kova ´cs a ,E ´ va Pa ´llinger b a Department of Genetics, Cell and Immunobiology, Semmelweis University, H-1445, Budapest, POB-370, Hungary b Molecular Immunological Research Group, Hungarian Academy of Sciences, H-1089, Budapest, Hungary Received 30 May 2005; accepted 23 August 2005 Abstract Using 1-ethyl-3(3-dimethyl-aminopropyl)-carbodiimide (EDAC) fixation and immunocytochemical confocal microscopic study, bright serotonin and histamine fluorescence appeared in the nucleus of rat peritoneal mast cells. In case of paraformaldehyde fixation, this was not observed. The phenomenon can be explained by the cross-linking effect of EDAC, which did not allow the efflux of biogenic amines from the nucleus. This means that biogenic amines are present in the nucleus of mast cells, and this is supported by the flow cytometric measurement data of the whole cell. Other hormones studied (triiodothyronine, insulin, and endorphin) were not present in the nucleus. Four pharmaca with biogenic amine-influencing character in the central nervous system were used for studying the relation between the external (surrounding and cytoplasmic) and nuclear biogenic amine content of mast cells. Fluoxetine, a serotonin reuptake inhibitor depleted nuclear as well as cytoplasmic serotonin content. Clorgyline, a MAO-A inhibitor, decreased cytoplasmic serotonin content and weakened nuclear serotonin fluorescence. The tryptophan hydroxylase inhibitor, para -chlorophenylalanine (PCPA), and the mast cell degranulator, Compound 48/80, reduced cytoplasmic serotonin content without influencing nuclear content. Histamine fluorescence was influenced solely by fluoxetine. The results show that nuclear 5-HT content is dependent firstly of serotonin uptake and reuptake. To our knowledge, this is the first exact report on the presence of non-steroid-type- receptor-transported hormones inside the nucleus of a cell. D 2005 Elsevier Inc. All rights reserved. Keywords: Serotonin; Histamine; Nuclear localization; Mast cell; EDAC-fixation; 5-HT inhibitors Introduction Different hormones, cytokines and neurotransmitters are produced, stored, taken up and secreted by white blood cells and mast cells. Lymphocytes, monocytes, granulocytes and mast cells contain triiodothyronine (Csaba et al., 2004, 2005) which has an immunomodulatory role (Bachman and Mashaly, 1987; Johnson et al., 1992) as well as insulin (Vafiadis et al., 1997; Pugliese et al., 1997; Kojima et al., 2004; Chentoufi and Polychronakos, 2002). Endorphin produced by immune cells help to calm pain during inflammation (Blalock, 1998; Panerai and Sacerdote, 1997). With the help of cytokines, there is a communication between immune cells (Schooltink and Rose- John, 2002; Haddad, 2002). Serotonin and histamine (which participates in many reactions, allergic included) of the immune system are main components of mast cells and basophils (Selye, 1965); however, they are also present in white blood cells (Csaba et al., 2002, 2003). While studying the serotonin content of immune cells by using antibodies and 0024-3205/$ - see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.lfs.2005.08.044 * Corresponding author. E-mail address: csagyor@dgci.sote.hu (G. Csaba). Table 1 Flow cytometrically measured serotonin content of rat peritoneal cells after paraformaldehyde or EDAC fixation Cell Fixation Geo-mean T S.D. Significance Lymphocyte Parafomaldehyde 19.7 T 6.25 EDAC 18.88 T 6.15 n.s. Mast cell Paraformaldehyde 45.23 T 8.74 EDAC 65.98 T 15.14 p < 0.03 Mo – gran Paraformaldehyde 30.09 T 8.08 EDAC 37.77 T 11.19 n.s. Mo-gran = monocyte – macrophage – granulocyte group; n.s. = not significant. Life Sciences 78 (2006) 1871 – 1877 www.elsevier.com/locate/lifescie