Endocrine and Local IGF-I in the Bony Fish Immune System

Abstract

A role for GH and IGF-I in the modulation of the immune system has been under discussion for decades. Generally, GH is considered a stimulator of innate immune parameters in mammals and teleost fish. The stimulatory effects in humans as well as in bony fish often appear to be correlated with elevated endocrine IGF-I (liver-derived), which has also been shown to be suppressed during infection in some studies. Nevertheless, data are still fragmentary. Some studies point to an important role of GH and IGF-I particularly during immune organ development and constitution. Even less is known about the potential relevance of local (autocrine/paracrine) IGF-I within adult and developing immune organs, and the distinct localization of IGF-I in immune cells and tissues of mammals and fish has not been systematically defined. Thus far, IGF-I has been localized in different mammalian immune cell types, particularly macrophages and granulocytes, and in supporting cells, but not in T-lymphocytes. In the present study, we detected IGF-I in phagocytic cells isolated from rainbow trout head kidney and, in contrast to some findings in mammals, in T-cells of a channel catfish cell line. Thus, although numerous analogies among mammals and teleosts exist not only for the GH/IGF-system, but also for the immune system, there are differences that should be further investigated. For instance, it is unclear whether the primarily reported role of GH/IGF-I in the innate immune response is due to the lack of studies focusing on the adaptive immune system, or whether it truly preferentially concerns innate immune parameters. Infectious challenges in combination with GH/IGF-I manipulations are another important topic that has not been sufficiently addressed to date, particularly with respect to developmental and environmental influences on fish growth and health.

Dietary administration of astaxanthin improves feed utilization, growth performance and survival of Asian seabass,Lates calcarifer(Bloch, 1790)

“…The results manifest that administration of supplementary astaxanthin in fish diet greatly elevated the levels of serum GH throughout the separate feeding phases. GH is a pituitary hormone, which plays a multifunctional role in numerous physiological processes such as growth promotion (Chang & Wong, ; Reindl & Sheridan, ), immune system function (Franz et al, ; Yada, ), reproduction (Benedet, Andersson, Mittelholzer, Taranger, & Bjornsson, ; Weber et al, ), osmoregulation (Sakamoto & McCormick, ; Varsamos, Nebel, & Charmantier, ), and behavioural function (appetite and swimming activity) (Devlin, Sakhrania, Tymchuka, Rise, & Goha, ; Hallerman, McLean, & Fleming, ; Jonsson, Johnsson, & Bjornsson, ), some of which may be closely interlinked in an intricate manner. There are no major efforts, thus far, that systematically elucidate the fundamental role of carotenoids in the modulation of fish GH, with only strong evidence linking to environmental and nutritional manipulations.…”

Signal Transduction for TNFα-Induced Type II SOCS Expression and Its Functional Implication in Growth Hormone Resistance in Carp Hepatocytes

“…Recently, the key members of type II SOCS, SOCS1-3 and CISH, have been cloned in grass carp and confirmed to be inducible by GH and serve as the feedback repressors for GH signaling via the JAK 2 /STAT 5 pathway with inhibitory effects on both basal and GH-induced IGF-I gene transcription at the hepatic level (41). In fish models, cytokine induction by microbial/viral infection [e.g., TNFα and interleukins in carp species (42,43)] and IGF-I modulation by cytokines [e.g., TNFα) have been reported [e.g., in immune cells/tissues of trout and sea bass, see (44) for a recent review]. In turbot, bacterial infection is also effective in increasing SOCS3 mRNA levels in various tissues including the liver and SOCS3 over-expression can inhibit TNFα and IL-1β expression in macrophages isolated from the head kidney (45).…”

Growth hormone transgenesis disrupts immune function in muscle of coho salmon (Oncorhynchus kisutch) impacting cross-talk with growth systems

“…Past work provides evidence for cross-talk between the GH and IGF pathways and the immune system (e.g. Heemskerk et al 1999; Yada, 2007; O’Connor et al, 2008; Smith, 2010; Franz et al, 2016). We recently reported that IGF signalling is repressed in rainbow trout (Oncorhynchus mykiss) in response to bacterial and viral infections, with a striking upregulation of IGFBP subtypes that restrict IGFs from IGF-1R, and potentially modify immune function (Alzaid et al, 2016a, 2016b).…”