Evolution of cytokine responses: IL-1beta directly affects intracellular Ca2+ concentration of teleost fish leukocytes through a receptor-mediated mechanism.
In this work we studied the biological activities of recombinant IL-1beta from the teleosts sea bass (Dicentrarchus labrax) and rainbow trout (Oncorhynchus mykiss) by investigating the effects induced on intracellular Ca2+ concentrations ([Ca2+]i) of spleen leucocytes. Splenocytes were loaded with the Ca2+-permeant Fura-2AM, and then stimulated with rIL-1beta. The emitted fluorescence was read for 5 min at 1 min intervals on a dual excitation fluorescence fluorimeter. Results showed that rIL-1beta induced in both species a rise in [Ca2+]i, and a subsequent decrease until 5 min after stimulation. The stimulating effect was dose-dependent in both species reaching a plateau at 200 ng/ml of rIL-1beta, was abolished by heat-treatment of rIL-1beta, and affected in a dose-dependent fashion by treatment of leucocytes with trypsin. These features suggested a functional IL-1 receptor was involved in the binding. The observed rise in [Ca2+]i was not detected in human PBMC and was species-specific, since rIL-1beta from sea bass, trout, and human were unable to interfere each other in the assay. Moreover, incubation of splenocytes with rIL-1beta induced a rapid tyrosine phosphorylation of a 24 kDa polypeptide in both species. This work represents the first evidence of a direct effect on [Ca2+]i induced by IL-1beta and suggests that in the evolution of IL-1 activities, teleost fishes display a peculiar IL-1-associated behaviour that is lacking in mammals.
Benedetti
S
S
Department of Environmental Sciences, University of Tuscia, I-01100 Viterbo, Italy.
Randelli
E
E
Buonocore
F
F
Zou
J
J
Secombes
C J
CJ
Scapigliati
G
G
D000818:Animals; D001492:Bass; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism*; D007962:Leukocytes / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000737:chemistry; D013045:Species Specificity; D013997:Time Factors; D014337:Trout; D014357:Trypsin / Q000737:chemistry / Q000494:pharmacology
D007375:Interleukin-1; D019000:Phosphotyrosine; D014357:Trypsin; D002118:Calcium