Cigarette smoke exposure inhibits contact hypersensitivity via the generation of platelet-activating factor agonists.
Previous studies have established that pro-oxidative stressors suppress host immunity because of their ability to generate oxidized lipids with platelet-activating factor receptor (PAF-R) agonist activity. Although exposure to the pro-oxidative stressor cigarette smoke (CS) is known to exert immunomodulatory effects, little is known regarding the role of PAF in these events. The current studies sought to determine the role of PAF-R signaling in CS-mediated immunomodulatory effects. We demonstrate that CS exposure induces the generation of a transient PAF-R agonistic activity in the blood of mice. CS exposure inhibits contact hypersensitivity in a PAF-R-dependent manner as PAF-R-deficient mice were resistant to these effects. Blocking PAF-R agonist production either by systemic antioxidants or treatment with serum PAF-acetyl hydrolase enzyme blocked both the CS-mediated generation of PAF-R agonists and PAF-R-dependent inhibition of contact hypersensitivity (CHS) reactions, indicating a role for oxidized glycerophosphocholines with PAF-R agonistic activity in this process. In addition, cyclooxygenase-2 inhibition did not block PAF-R agonist production but prevented CS-induced inhibition of CHS. This suggests that cyclooxygenase-2 acts downstream of the PAF-R in mediating CS-induced systemic immunosuppression. Moreover, CS exposure induced a significant increase in the expression of the regulatory T cell reporter gene in Foxp3(EGFP) mice but not in Foxp3(EGFP) mice on a PAF-R-deficient background. Finally, regulatory T cell depletion via anti-CD25 Abs blocked CS-mediated inhibition of CHS, indicating the potential involvement of regulatory T cells in CS-mediated systemic immunosuppression. These studies provide the first evidence, to our knowledge, that the pro-oxidative stressor CS can modulate cutaneous immunity via the generation of PAF-R agonists produced through lipid oxidation.
Department of Dermatology, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Ravi P
RP
Sahu
Irina
I
Petrache
Mary J
MJ
Van Demark
Badri M
BM
Rashid
Jesus A
JA
Ocana
Yuxuan
Y
Tang
Qiaofang
Q
Yi
Matthew J
MJ
Turner
Raymond L
RL
Konger
Jeffrey B
JB
Travers
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D003877:Dermatitis, Contact / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D004139:Dinitrofluorobenzene; D005260:Female; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D005997:Glycerylphosphorylcholine / Q000276:immunology / Q000378:metabolism*; D006867:Hydrolases / Q000378:metabolism; D007165:Immunosuppression Therapy; D015227:Lipid Peroxidation / Q000187:drug effects; D008212:Lymphocyte Depletion; D051379:Mice; D008822:Mice, Transgenic; D010972:Platelet Activating Factor / Q000235:genetics / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012906:Smoke / Q000009:adverse effects*; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D014026:Nicotiana / Q000009:adverse effects*
D000975:Antioxidants; D052246:Cyclooxygenase 2 Inhibitors; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D043562:Receptors, G-Protein-Coupled; D012906:Smoke; C039351:platelet activating factor receptor; D005997:Glycerylphosphorylcholine; D004139:Dinitrofluorobenzene; D051546:Cyclooxygenase 2; D006867:Hydrolases