title: Temperature-induced transcription of inflammatory mediators and the influence of Hsp70 following LPS stimulation of southern bluefin tuna peripheral blood leukocytes and kidney homogenates.
abstract: Temperature is known to influence inflammatory signalling in mammals, but far less understood in fish. The aim of the present study was to explore the potential effects of temperature on innate immune signalling in head kidney and leukocyte populations of the economically important southern bluefin tuna through the identification and utilization of gene expression targets in vitro. Here, we identified the mRNA sequences of five potential inflammatory mediators - TNFα (1 and 2), IL-1β, IL-8, and Cox2 - and demonstrate induction of four - TNFα (2), IL-1β, IL-8, and Cox2 - following LPS stimulation of both peripheral blood leukocytes and head kidney homogenates in vitro by real-time quantitative PCR. Comparison of transcriptional expression in cultures held at 18 and 25 °C (both within the presumed natural temperature range of this heterothermic species) showed accelerated transcription of cytokines TNFα, IL-1β and IL-8 following LPS stimulation at 25 °C in both tissue types. Peak induction reached comparable levels for each transcript at both temperatures during the 24 h test period with only limited (if any) protraction in expression resulting from cold temperature (18 °C) incubation. Partial mRNA sequences were also identified for both the constitutively expressed and heat inducible chaperone proteins Hsc70 and Hsp70, and 24 h incubation at 25 °C was sufficient to induce Hsp70 transcription in leukocyte but not in head kidney cell populations. Taken together these findings suggest that temperature exerts influence in the timing but not the degree of an innate inflammatory response in bluefin tuna and that different cell populations have differential responsiveness to heat shock in this heterothermic species. Further, LPS stimulation failed to induce Hsp70 at either incubation temperature in leukocytes; whereas 25 °C incubation caused Hsp70 up-regulation in leukocytes with or without the presence of LPS. This suggests that Hsp70 does not play a direct role in immune responsiveness for this species and that an environmental temperature of 25 °C in excess of 24 h initiates a cellular stress response in blood cells of this organism. Lastly, a strong correlation between Hsp70 and IL-8 transcriptional expression was observed following LPS/heat shock stimulation of leukocytes and five potential heat shock response elements were subsequently identified on the gene promoter region of IL-8 indicating that heat shock co-activation of this chemokine previously identified in mammals is also likely present in fish.
authors: National Centre for Marine Conservation and Resource Sustainability, Australian Maritime College, University of Tasmania, Locked Bag 1370, Launceston, TAS 7250, Australia. mark.polinski@utas.edu.au
authors: Mark
authors: M
authors: Polinski
authors: Andrew
authors: A
authors: Bridle
authors: Barbara
authors: B
authors: Nowak
mesh_terms: D000818:Animals; D001483:Base Sequence; D051546:Cyclooxygenase 2 / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000276:immunology; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D018869:Heat-Shock Response; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000502:physiology; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020539:Sequence Analysis, Protein; D017385:Sequence Homology; D015398:Signal Transduction; D014413:Tuna / Q000235:genetics* / Q000276:immunology / Q000382:microbiology / Q000502:physiology
chemical_list: D016207:Cytokines; D018076:DNA, Complementary; D029941:Fish Proteins; D018840:HSP70 Heat-Shock Proteins; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D051546:Cyclooxygenase 2