Exogenous Nitric Oxide Suppresses in Vivo X-ray-Induced Targeted and Non-Targeted Effects in Zebrafish Embryos.

E.Y Kong,W.K Yeung,T.K.Y Chan,K.N Yu,S.H Cheng

doi:10.3390/ijms17081321

E.Y Kong, W.K Yeung + Show 3 more

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https://doi.org/10.3390/ijms17081321

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Abstract

The present paper studied the X-ray-induced targeted effect in irradiated zebrafish embryos (Danio rerio), as well as a non-targeted effect in bystander naïve embryos partnered with irradiated embryos, and examined the influence of exogenous nitric oxide (NO) on these targeted and non-targeted effects. The exogenous NO was generated using an NO donor, S-nitroso-N-acetylpenicillamine (SNAP). The targeted and non-targeted effects, as well as the toxicity of the SNAP, were assessed using the number of apoptotic events in the zebrafish embryos at 24 h post fertilization (hpf) revealed through acridine orange (AO) staining. SNAP with concentrations of 20 and 100 µM were first confirmed to have no significant toxicity on zebrafish embryos. The targeted effect was mitigated in zebrafish embryos if they were pretreated with 100 µM SNAP prior to irradiation with an X-ray dose of 75 mGy but was not alleviated in zebrafish embryos if they were pretreated with 20 µM SNAP. On the other hand, the non-targeted effect was eliminated in the bystander naïve zebrafish embryos if they were pretreated with 20 or 100 µM SNAP prior to partnering with zebrafish embryos having been subjected to irradiation with an X-ray dose of 75 mGy. These findings revealed the importance of NO in the protection against damages induced by ionizing radiations or by radiation-induced bystander signals, and could have important impacts on development of advanced cancer treatment strategies.

Highlights

Nitric oxide (NO) is an important biological mediator in biological systems, and is involved in many different pathways such as immune response, neurotransmission and vasodilatation [1]
These effects were assessed using the number of apoptotic events in the zebrafish embryos at 24 hpf revealed through acridine orange (AO) staining, which was a common adopted biological endpoint for studying radiation-induced effects in zebrafish embryos [20]
The present paper studied X-ray-induced targeted and non-targeted effects in zebrafish embryos and examined the influence of exogenous NO generated using SNAP on these effects, with the number of apoptotic events in the embryos at 24 hpf revealed through AO staining as the biological endpoint

Summary

Introduction

Nitric oxide (NO) is an important biological mediator in biological systems, and is involved in many different pathways such as immune response, neurotransmission and vasodilatation [1]. NOS can be categorized into two functional classes, namely, the calcium-dependent constitutive NOS (cNOS) and the calcium-independent inducible NOS (iNOS) [2]. NO is involved in both targeted effects as well as non-targeted bystander effects induced by ionizing radiations. Ionizing radiations can activate the ataxia telangiectasia mutated (ATM)-NF-κB signaling pathway [4]. NF-κB enters the nucleus and acts as a transcription factor for cyclooxygense-2 (COX-2) and iNOS genes. Secreted or membrane-associated forms of cytokines, such as TNFα, can activate IκB kinase (IKK)-mediated phosphorylation of IκB, which releases NF-κB that enters the nucleus. TNFα activates MAPK pathways that, via AP-1 transcription factor, upregulate expression of COX-2 [6] and iNOS. Activation of COX-2 provided a continuous supply of reactive radicals and cytokines for the propagation of bystander signals [9]. NO has some intriguing properties in that it can lead to opposite biological functions, e.g., NO can be both pro-apoptotic and anti-apoptotic [10,11]

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