Immunohistochemical Investigation of Interaction Between Nesfatin-1 and Orexin A Neurons

Abstract

Nesfatin-1 and orexin A are oppositely acting two peptides, while nesfatin-1 suppresses food intake, orexin A stimulates this function. These peptides are synthesized and secreted by neuron groups located in the hypothalamus. In this study, the possible interactions between these two important peptidergic systems that play a role in the regulation of food intake were investigated by using immunohistochemical methods. As a result of the administration of the related peptides to the animals, the activational changes in the neurons synthesizing the other peptides were investigated. In addition to the c-Fos protein which is a transcription factor, we used different cellular signal pathway activation markers such as phosphorylated STAT5 (signal transducers and transcription activators) as well as p-CREB (c-AMP-responsive element binding protein). In these studies, the nesfatin neurons that are localized in the hypothalamic supraoptic nuclei and orexin neurons that are localized in the lateral hypothalamus were examined. The results showed that the nesfatin-1 axons are found to be juxta-positioned on the orexin neurons in order to form a possible synapse. However expression pattern of the c-Fos, pCREB or pSTAT5 proteins in the orexin A neurons showed no difference following the nesfatin-1 injections. Similarly no activation was assessed in the nesfatin-1 neurons after orexin administration. In conclusion, it is suggested that the nesfatin-1 neurons may form synaptic interactions with orexin A neurons, these two neurons cannot activate each other through c-Fos, CREB or STAT proteins, however other molecules may use these pathways in order to regulate these neurons as well as the food intake mechanism.

Keywords

• Nesfatin-1,Orexin A,c-Fos,Immunohistochemistry,Rat

Nesfatin-1 ve Oreksin A Nöronları Arasındaki Etkileşimin İmmünohistokimyasal Olarak Araştırılması

Abstract

Nesfatin-1 besin alımını baskılayan, oreksin A ise tetikleyen birbirine zıt etkili iki peptidtir. Bu peptidler hipotalamusta yerleşik olan nöron grupları tarafından sentezlenmekte ve salıverilmektedir. Çalışmamız kapsamında, besin alımının düzenlenmesinde rol oynayan bu iki önemli peptiderjik sistemin birbirleri üzerindeki olası etkileşimi immünohistokimyasal yöntemlerle araştırılmıştır. Bu amaca yönelik olarak, ilgili peptidlerin deneklere verilmesi sonucu diğer peptidi sentezleyen nöronlardaki aktivasyon değişiklikleri incelenmiştir. Bir transkripsiyon faktörü olan c-Fos proteininin yanı sıra, iki farklı hücre içi yolağın aktivasyon belirteci olan fosforile STAT5 (sinyal çevrimcileri ve transkripsiyon aktivatörleri) ve fosforile CREB (c-AMP-yanıtlı element bağlayıcı protein, p-CREB) immün reaktivitesinin varlığı, nöronal aktivasyonun belirlenmesinde kullanılmıştır. Çalışmalarda hipotalamusun supraoptik çekirdeklerinde lokalize nesfatin nöronları ile lateral hipotalamusta lokalize oreksin A nöronları incelenmiştir.Çalışmaların sonucunda nesfatin-1 nöronlarına ait aksonların, oreksin A nöronları üzerinde sinaps oluşturabileceğini düşündürecek şekilde sonlanmalar yaptığı görülmüştür. Ancak nesfatin-1 verilen deneklerin oreksin A nöronlarında c-Fos, pCREB veya pSTAT5 proteinlerinin ekspresyonunda bir değişiklik görülmemiştir. Benzer şekilde oreksin A verilen deneklere ait nesfatin-1 nöronlarında da bu belirteçleri içeren yolaklara ait bir aktivasyon gözlenmemiştir. Sonuç olarak, nesfatin-1 nöronlarının oreksin A nöronlarıyla sinaps oluşturabileceği, nesfatin-1 ve oreksin A peptidlerinin birbiri üzerinde, c-Fos, CREB ve STAT proteinlerinin rol aldığı hücre içi yolakları kullanarak aktive edici etkilerinin olmadığı, ancak her iki peptidi eksprese eden nöronlarda, bu yolakların kullanımıyla farklı moleküllerin besin alımının kontrolü doğrultusunda düzenleyici etki gösterebilecekleri düşünülmüştür.

Keywords

• Nesfatin-1,Oreksin A,c-Fos,İmmünohistokimya,Sıçan

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