Temperature-induced transcription of inflammatory mediators and the influence of Hsp70 following LPS stimulation of southern bluefin tuna peripheral blood leukocytes and kidney homogenates
Polinski, M and Bridle, AR and Nowak, BF, Temperature-induced transcription of inflammatory mediators and the influence of Hsp70 following LPS stimulation of southern bluefin tuna peripheral blood leukocytes and kidney homogenates, Fish and Shellfish Immunology, 34, (5) pp. 1147-1157. ISSN 1050-4648 (2013) [Refereed Article]
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 e TNFa (1 and 2), IL-1b, IL-8, and Cox2 e and
demonstrate induction of four e TNFa (2), IL-1b, IL-8, and Cox2 e 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
TNFa, IL-1b 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 coactivation of this chemokine previously identified in mammals is also likely present in fish.