Transcriptomic analysis of the impacts of ethinylestradiol (EE2) and its consequences for proliferative kidney disease outcome in rainbow trout (Oncorhynchus mykiss)

Abstract

Freshwater fish are threatened by the cumulative impact of multiple stressors. The purpose of this study was to unravel the molecular and organism level reactions of rainbow trout, Oncorhynchus mykiss, to the combined impact of two such stressors that occur in the natural habitat of salmonids. Fish were infected with either the myxozoan parasite, Tetracapsuloides bryosalmonae, which causes proliferative kidney disease (PKD), or exposed to ethinylestradiol (EE2) an estrogenic endocrine disrupting compound, or to a combination of both (PKD x EE2). PKD is a slow progressive chronic disease here we focused on a later time point (130-day postinfection (d.p.i)) when parasite intensity in the fish kidney has already started to decrease. At 130 d.p.i, RNA-seq technology was applied to the posterior kidney, the main target organ for parasite development. This resulted with 280 (PKD), 14 (EE2) and 444 (PKD x EE2) differentially expressed genes (DEGs) observed in the experimental groups. In fish exposed to the combination of stressors (PKD x EE2), a number of pathways were regulated that were neither observed in the single stressor groups. Parasite infection, alone and in combination with EE2, only resulted in a low intensity immune response that negatively correlated with an upregulation of genes involved in a variety of metabolic and inflammation resolution processes. This could indicate a trade-off whereby the host increases investment in recovery/resolution processes over immune responses at a later stage of disease. When PKD infection took place under simultaneous exposure to EE2 (PKD x EE2), parasite intensity decreased and pathological alterations in the posterior kidney were reduced in comparison to the PKD only condition. These findings suggest that EE2 modulated these response profiles in PKD infected fish, attenuating the disease impact on the fish.

Back From the Brink: Alterations in B and T Cell Responses Modulate Recovery of Rainbow Trout From Chronic Immunopathological Tetracapsuloides bryosalmonae Infection

“…It could be presumed that as the disease recovery continues an upregulation of macrophage markers or M2 phenotypes could feature in tissue resolution. For instance, in a late stage PKD investigation (taking place solely at day 130 P.E = 19.5 weeks P.E) using an RNA-seq approach, slc11a1 (formerly known as nrampα) and mcsf were both significantly upregulated (relative to the control) in the PK of fish exposed to T. bryosalmonae and an endocrine disrupting compound ethinylestradiol (36). However, these genes were not upregulated in fish only exposed to the parasite (36).…”

“…For instance, in a late stage PKD investigation (taking place solely at day 130 P.E = 19.5 weeks P.E) using an RNA-seq approach, slc11a1 (formerly known as nrampα) and mcsf were both significantly upregulated (relative to the control) in the PK of fish exposed to T. bryosalmonae and an endocrine disrupting compound ethinylestradiol (36). However, these genes were not upregulated in fish only exposed to the parasite (36). While, in the present study, the expression of mcsf occurred when almost every measured gene was upregulated before the molecule was downregulated at week 10 P.E at which time many transcripts were also downregulated, thus the regulation of this gene may be more indicative of a global transcriptional shift in immune response linked to the parasite.…”

Comparative transcriptomics and host-specific parasite gene expression profiles inform on drivers of proliferative kidney disease

“…To detect proteases in the intersect transcriptome, all contigs were analysed using the MEROPS database. A total of 100 proteases homologous to metallo- (44) and cysteine (26) proteases, threonine (12), serine (11), aspartate (5) and asparagine proteases (2) were recovered ( Supplementary Table S3 and Fig. 4A).…”

“…In mammals, tetraspanins in the CD family are important immune regulators with hematopoietic-specific CD53 being a suppressor of inflammatory cytokines 41,42 . Thus, association between T. bryosalmonae ADAM and tetraspanin homologues may, in part, be responsible for T. bryosalmonae-mediated disease pathology and dampening of fish proinflammatory responses observed during PKD 11,43 . Similarly, the T lymphocyte hormone TMSB4, dampens inflammatory processes by influencing TLR activity.…”

“…Extrasporogonic proliferation of T. bryosalmonae in kidney tissues elicits a chronic tissue pathology, characterised by lymphoid hyperplasia, granulomatous lesions, renal atrophy, anaemia 7,8 and hyper secretion of immunoglobulins 9,10 . The severity and development of these hallmark symptoms of PKD are modified by a variety of biological, environmental and chemical stressors, impacting on parasite load, host immunity, and disease recovery 10,11 . A genetic basis for such pathological and developmental variation is evidenced by introduced, non-co-evolved salmonid hosts in Europe, such as rainbow trout, acting as dead-end hosts.…”