LPS Modulates the Expression of Iron-Related Immune Genes in Two Antarctic Notothenoids

Abstract

The non-specific immunity can induce iron deprivation as a defense mechanism against potential bacterial pathogens, but little information is available as to its role in Antarctic fish. In this study the response of iron metabolism related genes was evaluated in liver and head kidney of the Antarctic notothenoids Notothenia coriiceps and Notothenia rossii 7 days after lipopolysaccharide (LPS) injection. Average plasma Fe 2+ concentration was unaffected by treatment in any of the species. The gene expression response to LPS varied between tissues and species, being stronger in N. coriiceps and more prominent in the head kidney than liver. The reaction to LPS was marked by increased individual variability in most genes analyzed, even when the change in expression was not statistically significant, suggesting different individual sensitivity and coping responses in these wild fish. We found that iron related genes had an attenuated and homogenous response to LPS but there was no detectable relationship between plasma Fe 2+ and gene expression. However, overall in both tissues and species LPS exposure set a multilevel response that concur to promote intracellular accumulation of iron, an indication that Antarctic Notothenoids use innate nutritional immunity as a resistance mechanism against pathogens.

PAMPs of Piscirickettsia salmonis Trigger the Transcription of Genes Involved in Nutritional Immunity in a Salmon Macrophage-Like Cell Line

“…Our results are consistent with those of Martínez et al. ( 8 ), who observed increased tfr1 , ireg1 and hamp transcription in the head kidney of N. coriiceps exposed to LPS. These authors suggest LPS triggers iron associated nutritional immune responses; however, they did not observe any changes in plasma iron concentrations or evaluate tissue iron concentrations.…”

“…( 9 ), who reported increased ireg1 transcription in the head kidney of S. salar families with low susceptibility to P. salmonis at 14 dpi ( 9 ) and for Martínez et al. ( 7 , 8 ), who reported increased ireg1 and hamp expression in E. maclovinus and N. coriiceps injected intraperitoneally with two strains of P. salmonis and LPS, respectively.…”

“…This defense mechanism is called nutritional immunity and involves depleting micronutrients such as iron, manganese and zinc from the circulation by sequestering them within the cells ( 5 ). Nutritional immunity in fish has been described in Eleginops maclovinus ( 6 , 7 ), Notothenia coriiceps ( 8 ), Notothenia rossii ( 8 ) and Salmo salar ( 9 ), being this latter the most important species in the Chilean aquaculture ( 10 ). Outbreaks of infectious diseases in S. salar farms cause substantial economic losses in the Chilean aquaculture industry every year.…”

“…On the other hand, Martínez et al. ( 8 ) reported that LPS modulates the expression of iron-related immune genes in N. coriiceps and N. rossi but does not affect the plasma iron concentrations ( 8 ). This latter research suggests that nutritional immunity may not differentiate between live pathogens (that need micronutrients to establish an infection) and PAMPs (that do not).…”

Toll-Like Receptor Evolution: Does Temperature Matter?

“…Differences in the responsiveness of N. rossii and N. coriiceps to an LPS challenge were previously reported in relation to iron metabolism genes ( 118 ) with N. coriiceps being more responsive. In the present study, increased seawater temperature had a more profound effect than LPS on tlr5 , tlr21 , and tlr22 gene expression in N. rossii .…”