Formation of histamine-releasing activity from albumin by medium conditioned by endotoxin-stimulated rat peritoneal macrophages

Abstract

Incubation of bovine serum albumin (BSA), rat serum albumin or rat plasma with medium conditioned by endotoxin stimulated rat peritoneal macrophages produced an activity that released histamine from isolated rat serosal mast cells. The amount of histamine-releasing activity (HRA) produced increased with the length of the incubation period, with the concentration of albumin, with the number of macrophages stimulated, and with the duration of exposure of the macrophages to endotoxin. Moreover, the formation of the HRA showed a dependency on the pH of the incubation medium with an optimum at pH 4.5. Boiling the medium conditioned by stimulated macrophages before its incubation with albumin or including the acid protease inhibitor, pepstatin with the conditioned medium prevented the formation of HRA. The generation of HRA was not inhibited by pretreatment of the macrophages with the inhibitor of protein synthesis, cycloheximide. Media from macrophages not stimulated with endotoxin failed to generate HRA. Histamine release from mast cells in response to the HRA was inhibited by pretreatment of the cells with antimycin A and deoxyglucose or by preincubation in Ca-free Locke's solution containing a calcium chelating agent. When injected intradermally into anesthetized Evan's Blue treated rats, the generated HRA produced a change in vascular permeability that was prevented by the H1 antagonist, diphenhydramine. Treatment of the HRA with carboxypeptidase A reduced its ability to stimulate histamine release from mast cells. Histamine-Releasing Peptide (HRP), a neurotensin-related octapeptide, shown previously by us to be formed by the action of cathepsin D or pepsin on albumin, was identified by radioimmunoassay in acid:acetone extracts of the histamine-releasing activity. It is concluded that the formation of HRA is due to the actions of enzymes released from macrophages acting on albumin. It is suggested that such histamine-releasing activity could be formed during the later stages of the inflammatory response and that HRP is one of the peptides present.

Involvement of Central Histamine in the Early Phase of ACTH and Corticosterone Responses to Endotoxin in Rats

“…Indeed, when stimulated by LPS, macrophages produce a histaminergic releasing factor from plasma albumin [42] that could gain access to the median eminence, a structure which has no blood-brain barrier. Increased CRH41 secretion may then result from local production in the median eminence [43,44], thereby initiating the whole HPA response to endotoxin.…”

Generation of VV‐hemorphin‐7 from globin by peritoneal macrophages

“…The peritoneal cells obtained in a single experiment (5 mice) were collected by ceutrifngation at 400×g for 10 rain at 4ec, Macrophages, identified by measuring neutral red uptake, were counted under phase contrast microscopy, The predominant cell type in such peritoneal exudates is the macrophage cell [21]. About l0 T cells per mouse were obtained and 80% were macrophnges.…”