Repeat organic dust exposure-induced monocyte inflammation is associated with protein kinase C activity.
BACKGROUND
Organic dust exposure results in an inflammatory response that attenuates over time, but repetitive exposures can result in chronic respiratory diseases. Mechanisms underlying this modulated response are not clear.


OBJECTIVE
This study investigated the effects of repeat versus single organic dust exposure-induced inflammatory mediators and protein kinase C (PKC) activity in monocytes.


METHODS
Settled organic dust was obtained from swine confinement facilities. Promonocytic THP-1 cells and human peripheral blood monocytes were pretreated with or without dust extract and then restimulated. Culture supernatants were evaluated for TNF-alpha, IL-6, CXCL8, and IL-10. Responses were compared with endotoxin-depleted dust, LPS, and peptidoglycan. PKC isoform (alpha, delta, epsilon, zeta) activation was evaluated by direct kinase activity. PKC isoform inhibitors' effects on TNF-alpha secretion were studied.


RESULTS
Single exposure to organic dust stimulated monocyte secretion of TNF-alpha, IL-6, CXCL8, and IL-10 compared with unstimulated cells. TNF-alpha and IL-6 were diminished in pretreated cells restimulated with dust. Secretion of CXCL8 and IL-10 remained persistently elevated. TNF-alpha responses were retained after marked depletion of endotoxin. Dust exposure induced significant PKC alpha, delta, epsilon, and zeta activation, peaking at 30 to 60 minutes. PKC isoform activation was attenuated in repeat exposed cells. Inhibition of PKCalpha and PKCepsilon reduced dust-induced TNF-alpha secretion.


CONCLUSIONS
Repeat organic dust exposure modulated inflammatory mediator production in monocytes independent of endotoxin. The inability of PKC to be reactivated may account for this observation.


CONCLUSIONS
Targeting PKC and specific mediators associated with repetitive organic dust exposure may result in novel therapeutic strategies.
Poole
Jill A
JA
Pulmonary, Critical Care, Sleep and Allergy Section, Department of Internal Medicine, University of Nebraska Medical Center, 985300 The Nebraska Medical Center, Omaha, NE 68198-5300, USA. japoole@unmc.edu
Wyatt
Todd A
TA
Von Essen
Susanna G
SG
Hervert
John
J
Parks
Conrad
C
Mathisen
Tracy
T
Romberger
Debra J
DJ
D000328:Adult; D000818:Animals; D002478:Cells, Cultured; D004391:Dust; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006799:Housing, Animal; D006801:Humans; D007249:Inflammation / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D018836:Inflammation Mediators / Q000378:metabolism*; D016753:Interleukin-10 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D009000:Monocytes / Q000473:pathology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013552:Swine; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004391:Dust; D004791:Enzyme Inhibitors; D018836:Inflammation Mediators; D015850:Interleukin-6; D016209:Interleukin-8; D007527:Isoenzymes; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D011493:Protein Kinase C