The Mechanism of Steroid-Induced Fever

Granulocytes and monocytes derived from inflammatory exudates or the peripheral circulation of several mammalian species (1-5) can be stimulated to release a pyrogen, leukocytic pyrogen (LP) 1, which induces a characteristic febrile response in rabbits. Chemical characterization of LP has shown it to be a protein molecule (6-8) and since the original discovery of its production by rabbit peritoneal exudate cells (9), many attempts have been made to determine the mechanism of its synthesis by leukocytes. With one exception (10), preformed pyrogen has not been obtained from disrupted rabbit cells (11,12). Its release in vitro has been shown to take place over a several hour period (4, 11, 12), to be dependent upon the temperature of incubation (11), and inhibited by agents which bind sulfhydryl groups in enzymes (13). These findings suggest that LP is either synthesized de novo or activated from a precursor substance after contact with an appropriate stimulating agent.In the present studies, the role of RNA and protein synthesis and the energy requirements for pyrogen release by human peripheral leukocytes activated by the ingestion of heat-killed bacteria have been investigated. The results reported here indicate that both transcription of messenger RNA and its translation by ribosomes into

Section: Discussionmentioning

confidence: 96%

Studies on the Origin of Human Leukocytic Pyrogen

Nordlund

Root

Wolff

1970

“…Similar findings have been obtained by Bodel, et al (11) with activation by phagocytosis and by etiocholanolone, and by Nordland et al (12) with activation by phagocytosis and by endotoxin. When, on the other hand, exudate leukocytes or activated blood leukocytes (see Tables X and XII) are incubated in 0.15 M NaC1, pyrogen production is not influenced by inhibitors of protein synthesis (9,11), since the cells have already been activated.…”

Section: Evidence That Activation Involves Synthesis Of Protein--thementioning

confidence: 99%

“…The activation step requires the synthesis of protein. The critical protein(s) synthesized may include an inactive precursor of the pyrogen molecule (propyrogen) or an enzyme needed to convert it to active pyrogen (11). Evidence is presented elsewhere that neither is synthesized during the release process (9) .…”

Section: Evidence That Activation Involves Synthesis Of Protein--thementioning

confidence: 99%

Studies on the Pathogenesis of Fever

Moore

Cheuk

Morton

et al. 1970

Rabbit blood leukocytes ~ contain no detectable preformed pyrogen (4) and produce much less pyrogen than exudate leukocytes (about 1/50) when incubated in 0.15 ~ NaC1 (4). 3 After phagocytosis (5) or exposure to endotoxin (6), 3 on the other hand, they produce about the same or even greater amounts of pyrogen than exudate leukocytes. These findings suggest that blood leukocytes must be "activated" to release pyrogen in 0.15 ~ NaC1, and that activation of blood leukocytes automatically takes place after phagocytosis or exposure to endotoxin. The following experiments deal with the process of activation and the presence of an activating factor in acute peritoneal exudates. Materials and MethodsThe procedures used to exclude exogenous pyrogens (7), to prepare suspensions of leukocytes from both rabbit blood (4) and acute peritoneal exudates (7), to generate pyrogen from the cells (7), to assay the amount of pyrogen released (7,8), and to measure the cellular contents and fluid concentrations of Na and K (5, 9) and the fuid concentration of Ca (5, 9) and of protein (7) have all been previously described. Endotoxin (lipopolysaccharide B from Escherichia coli 011 l:B4) was purchased from Difco Laboratories, Detroit, Mich., and cycloheximide (Acti-dione), puromycin dihydrochloride, and acfinomycin D were obtained from Nutritional Biochemicals Corp., Cleveland, Ohio.

“…Nor do they support the suggestion that its conversion from an inactive to an active form during release involves the synthesis of new protein, e.g., enzyme(s) (20). Rather they favor the concept that pyrogen is stored in the cells as an inactive precursor (propyrogen), which is converted to active pyrogen just prior to its release from the cells.…”

Section: Studies On Pathogenesis Of Fever XIXmentioning

confidence: 89%

Studies on the Pathogenesis of Fever

Hahn

Cheuk

Elfenbein

et al. 1970

Only intact exudate granulocytes from rabbits generated large amounts of endogenous pyrogen when incubated in 0.15 M NaCl. No matter how whole-cell lysates or combinations of subcellular fractions were incubated, their yields of pyrogen never approached those of whole cells; at most, only minimal amounts of pyrogen were formed, once the integrity of the cells had been destroyed. Some pyrogen could be extracted from disrupted cells, but never more than a fraction (<25%) of that released from incubated whole cells. The yield could be slightly improved by lowering the pH (to 3.5) and by increasing the volume of extraction fluid. Virtually all of the preformed pyrogen that could be extracted from sucroselysed cells was found in their cytoplasmic fraction. Contrary to the results of Herion et al. (3), none could be detected in the granular (or lysosomal) fraction. Likewise, all efforts to recover pyrogen from the membrane-nuclear fraction were unsuccessful. In keeping with the finding that preformed pyrogen is contained in the cytoplasmic fraction were the observations that practically all of the aldolase, a cytoplasmic enzyme, and very little of the acid phosphatase, a granular enzyme, were lost from the cells during the release of pyrogen. Lysozyme, an enzyme stored in both the granules and the cytoplasm, was partially released from the cells under the same circumstances. Neither the release of pyrogen nor its slight intracellular buildup that precedes release (4) were affected by concentrations of puromycin that block protein synthesis in the cells and prevent their activation. Hence, it is concluded that the release process, which also involves the formation of active pyrogen (4), does not require protein synthesis, whereas activation of the cells, which may involve the synthesis of an inactive precursor (2), does.