Radiation induced bystander effect: mechanisms and potential clinical reflections

Abstract

A long held dogma in radiation biology has been that the effects of ionizing radiation arise only in the directly irradiated cells, and it was presumed that no effect would be expected in cells whose nuclei are spared from ionizing radiation. However, in the past twenty years, it has been suggested that irradiated cells are capable of production and secretion of signals to the neighboring unirradiated cells resulting in damage to these cells. This new challenging phenomenon is termed “the bystander effect”. Bystander effect can be reported in both cytoplasmic and nuclear irradiation in various cell types. Although the exact mechanisms of bystander effect production is not clearly defined yet, intercellular communication via gap junctions and lipid rafts, and secreted paracrine and endocrine soluble factors are potential suggested mechanisms. By this review article it has been aimed to summarize these mechanisms and the clinical reflections of bystander effect.

Keywords

• Bystander Effect,Cell Communication,Linear Energy Transfer,Radiation Effects

Radyoterapiye bağlı “bystander” etki: Oluşum mekanizmaları ve potansiyel klinik yansımalar

Öz

Günümüzde, genel radyobiyoloji anlayışına bir yenilik olarak, radyasyona maruz kalmamış komşu veya uzak hücre gruplarında da radyasyona maruz kalmış olanlara benzer biyolojik etkilerin görüldüğüne dair giderek artan miktarda kanıt oluşmaya başlamıştır. Bystander etki olarak adlandırılan bu etkiler deneysel olarak geniş bir hücre grubunda çekirdek ve sitoplazma radyasyon maruziyeti sonrasında görülebilmektedir. Bystander e tki sonucunda sağlam hücre gruplarında da bazı önemli genetik değişiklikler söz konusu olduğundan bu etkilerin karsinogenez açısından önemi de cevap bekleyen sorulardandır. Bystander etki oluşum mekanizmaları tam olarak bilinmese de hücre zarında bulunan gap junction'lar ve lipid boşlukların yanı sıra radyasyona maruz kalmış hücreler tarafından salınan parakrin ve endokrin faktörlerin rolü üzerinde durulmaktadır. Bu yazıda radyobiyolojinin yeni bir alanı olan bystander etkinin temel oluşum mekanizmalarından potansiyel klinik uygulamalarına kadar olan yeni literatür bilgilerinin özetlenmesi amaçlandı.

Anahtar Kelimeler

• Bystander etki/radyasyon etkisi, hücreler arası iletişim/radyasyon etkisi, lineer enerji transferi

Kaynakça

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