Differential response to a stress stimulus of proenkephalin peptide content in immune cells of naive and chronically stressed rats.
Proenkephalin peptides produced by endocrine and nervous tissues are involved in stress-induced immunosuppression. However, the role of peptides produced by immune cells remains unknown. The present study examines the effect of acute and chronic foot-shock stress on proenkephalin peptide content in bone marrow (BMMC), thymus (TMC), and spleen (SMC) rat mononuclear cells. Proenkephalin was not processed to met-enkephalin in BMMC, while in TMC and SMC met-enkephalin represented 10% and 26% of total met-enkephalin-containing peptides, respectively. Naive rats receiving a stress stimulus showed a significant decrease of proenkephalin derived peptides in BMMC, TMC and SMC. However, in chronically stressed rats that already showed basal low peptide levels, a new stress stimulus produced a differential response in each immune tissue. That is, in BMMC peptide levels reached control rats values; in TMC remained unmodified; and in SMC, although precursors content increased, met-enkephalin levels were even lower than those observed in acutely stressed rats. Free synenkephalin content paralleled met-enkephalin changes in SMC of acutely and chronically stressed rats. The in vitro release of met-enkephalin and free synenkephalin increased in SMC of stressed rats. Met-enkephalin produced in SMC and partially processed proenkephalin peptides detected in BMMC, were only found in macrophages. However, met-enkephalin only appeared in bone marrow macrophages after at least 4 h of cell culture. Altogether, these results suggest that a stress stimulus induced proenkephalin peptide release from immune tissue macrophages. The differential response observed in chronically stressed rats suggest an alternative activation of heterogeneous proenkephalin-storing macrophage subpopulations.
Saravia
F
F
Instituto de Fisiologia, Laboratorio de Bioquimica, Universidad Autonoma de Puebla, Mexico.
Padros
M R
MR
Ase
A
A
Aloyz
R
R
Duran
S
S
Vindrola
O
O
D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism*; D004597:Electroshock; D004744:Enkephalin, Methionine / Q000378:metabolism; D004745:Enkephalins / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D008297:Male; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000166:cytology / Q000378:metabolism*; D013312:Stress, Physiological / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism*
D004745:Enkephalins; D011498:Protein Precursors; C029992:proenkephalin; D004744:Enkephalin, Methionine