Photoinduced cutaneous inflammatory response by psoralens.
Our studies describe the inflammatory response in rabbit skin induced by topical application of 8-methoxypsoralen (8-MOP) and UVA-visible irradiation (320-700 nm). Increase in vascular permeability (iVP) and accumulation of polymorphonuclear leucocytes (aPMN) at the test sites were quantitated using 125I-albumin and 51Cr-labelled PMNs respectively. Erythema was graded visually. 8-MOP cream was applied topically and irradiated. The erythemal response, aPMN and iVP at the test sites were quantitated at 6, 24, 48 and 72 h post-irradiation. The iVP and aPMN were maximal at 24 h; the erythemal response was the same at 24-48 h. The responses were dependent on 8-MOP concentration and irradiation dose. Topical application of 200 micrograms 8-MOP cream followed by irradiation for 2 h (9.4 J cm-2) produced 3-7 times iVP, 2-4 times aPMN and intense erythema at the test sites after 24 h. Neither aPMN nor iVP was detected before 6 h and erythemal response was not observable up to 16 h after irradiation. The aPMN and iVP gradually subsided in 72 h, although the erythemal response was still present. The repeated exposure of 8-MOP-treated sites for three consecutive days 24 h apart did not produce appreciable iVP or aPMN at 72 h or 24 h after the last exposure; however, erythema persisted. The 8-MOP-treated sites previously exposed for three consecutive days on reapplication of 8-MOP cream plus irradiation showed significantly less response compared with non-pretreated sites. Our results suggest that the erythemal response is not directly related to either iVP or aPMN.
Kumar
J R
JR
Department of Pathology, University of Toronto, Ont., Canada.
Ranadive
N S
NS
Menon
I A
IA
Haberman
H F
HF
D000287:Administration, Topical; D000818:Animals; D003624:Darkness; D004305:Dose-Response Relationship, Drug; D004890:Erythema / Q000503:physiopathology; D007249:Inflammation; D008027:Light; D008297:Male; D008730:Methoxsalen / Q000008:administration & dosage / Q000633:toxicity*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D011817:Rabbits; D012016:Reference Values; D012039:Regional Blood Flow / Q000187:drug effects / Q000528:radiation effects; D012867:Skin / Q000187:drug effects / Q000473:pathology* / Q000528:radiation effects; D014466:Ultraviolet Rays
D008730:Methoxsalen