Are Pathogens Completely Harmful or Useless?

Potential dsRNAs can be delivered to aquatic for defense pathogens

The use of antibiotics to facilitate resistance to pathogens in aquatic animals is a traditional method of pathogen control that is harmful to the environment and human health. RNAi is an emerging technology in which homologous small RNA molecules target specific genes for degradation, and it has already shown success in laboratory experiments. However, further research is needed before it can be applied in aquafarms. Many laboratories inject the dsRNA into aquatic animals for RNAi, which is obviously impractical and very time consuming in aquafarms. Therefore, to enable the use of RNAi on a large scale, the methods used to prepare dsRNA need to be continuously in order to be fast and efficient. At the same time, it is necessary to consider the issue of biological safety. This review summarizes the key harmful genes associated with aquatic pathogens (viruses, bacteria, and parasites) and provides potential targets for the preparation of dsRNA; it also lists some current examples where RNAi technology is used to control aquatic species, as well as how to deliver dsRNA to the target hydrobiont.

Vitamin C rescues inflammation, immunosuppression, and histopathological alterations induced by chlorpyrifos in Nile tilapia

Chlorpyrifos (CPF) is an extensive environmental contaminant and disrupts the physiological status of living organisms. CPF is found to hinder the health of aquatic organisms and ecological function in aquatic systems. The current study aimed at evaluating the protective effects of vitamin C (VC) on the immune response, hematological parameters, and histopathological alterations in Nile tilapia exposed to CPF. Nile tilapia were exposed to waterborne CPF (15 μg/L) for 30 days. Fish were divided into control group: received basal diet; CPF group: received basal diet and exposed to waterborne CPF; VC group: received basal diet plus 0.8 mg VC/kg; and CPF/VC group: received basal diet plus 0.8 mg VC/kg and exposed to waterborne CPF. Blood samples were taken after 15 days and 30 days of the treatment. Liver, gills, and intestine tissues were collected on the 30th day of treatment. CPF showed a deleterious effect on fish's growth performance; it decreased the weight gain by 6%, while VC increased it by 17-23% compared to the control group. CPF group recorded the lowest survival rate (83%), while VC achieved survivability of 96.7% and 93.3% in VC and CPF/VC groups, respectively. The blood picture revealed moderate changes in the CPF group, where the marked alteration was in the hemoglobin concentration and white blood cells. CPF disrupted the hepatic and renal function. Serum lysozyme activity, phagocytic activity, and phagocytic index displayed a dramatic decline in the CPF group but enhanced in VC and CPF/VC groups. An upregulation was observed in antioxidant genes (catalase and glutathione peroxidase), heat shock protein 70, caspase-3, and the cytokines interleukin 1β, interleukin 8, and interferon-gamma in the CPF group. Simultaneously, moderate or normal levels were shown in the VC and CPF/VC groups. CPF altered the histoarchitecture of gills, intestine, and hepatopancreas with apparent degenerative changes possibly resulted from the oxidative stress. At the same time, VC retained the normal structure of the studied tissues. This study raises concerns about the safety of CPF and its impact on the aquatic environment. VC has a high potential to restore the normal physiology of fish exposed to CPF.

The emerging regulatory roles of noncoding RNAs in immune function of fish: MicroRNAs versus long noncoding RNAs

The genome could be considered as raw data expressed in proteins and various types of noncoding RNAs (ncRNAs). However, a large portion of the genome is dedicated to ncRNAs, which in turn represent a considerable amount of the transcriptome. ncRNAs are modulated on levels of type and amount whenever any physiological process occurs or as a response to external modulators. ncRNAs, typically forming complexes with other partners, are key molecules that influence diverse cellular processes. Based on the knowledge of mammalian biology, ncRNAs are known to regulate and control diverse trafficking pathways and cellular activities. Long noncoding RNAs (lncRNAs) notably have diverse and more regulatory roles than microRNAs. Expanding these studies on fish has derived the same conclusion with relevance to other species, including invertebrates, explored the potentials to harness such types of RNA to further understand the biology of such organisms, and opened gates for applying recent technologies, such as RNA interference and delivering micromolecules as microRNAs to living cells and possibly to target organs. These technologies should improve aquaculture productivity and fish health, as well as help understand fish biology.

RNA Interference in Aquaculture: A Small Tool for Big Potential

For decades, the tight regulatory functions of DNA and RNA have been the focus of extensive research with the goal of harnessing RNA molecules (e.g., microRNA and small interfering RNA) to control gene expression and to study biological functions. RNA interference (RNAi) has shown evidence of mediating gene expression, has been utilized to study functional genomics, and recently has potential in therapeutic agents. RNAi is a natural mechanism and a well-studied tool that can be used to silence specific genes. This method is also used in aquaculture as a research tool and to enhance immune responses. RNAi methods do have their limitations (e.g., immune triggering); efficient and easy-to-use RNAi methods for large-scale applications need further development. Despite these limitations, RNAi methods have been successfully used in aquaculture, in particular shrimp. This review discusses the uses of RNAi in aquaculture, such as immune- and production-related issues and the possible limitations that may hinder the application of RNAi in the aquaculture industry. Our challenge is to develop a highly potent in vivo RNAi delivery platform that could complete the desired action with minimal side effects and which can be applied on a large-scale with relatively little expense in the aquaculture industry.

Exploring the role of microRNAs in axolotl regeneration

The axolotl, Ambystoma mexicanum, is used extensively for research in developmental biology, particularly for its ability to regenerate and restore lost organs, including in the nervous system, to full functionality. Regeneration in mammals typically depends on the healing process and scar formation with limited replacement of lost tissue. Other organisms, such as spiny mice (Acomys cahirinus), salamanders, and zebrafish, are able to regenerate some damaged body components. Blastema is a tissue that is formed after tissue injury in such organisms and is composed of progenitor cells or dedifferentiated cells that differentiate into various cell types during regeneration. Thus, identifying the molecules responsible for initiation of blastema formation is an important aspect for understanding regeneration. Introns, a major source of noncoding RNAs (ncRNAs), have characteristic sizes in the axolotl, particularly in genes associated with development. These ncRNAs, particularly microRNAs (miRNAs), exhibit dynamic regulation during regeneration. These miRNAs play an essential role in timing and control of gene expression to order and organize processes necessary for blastema creation. Master keys or molecules that underlie the remarkable regenerative abilities of the axolotl remain to be fully explored and exploited. Further and ongoing research on regeneration promises new knowledge that may allow improved repair and renewal of human tissues.