Histamine Is Released following Aminolevulinic Acid-Photodynamic Therapy of Human Skin and Mediates an Aminolevulinic Acid Dose-Related Immediate Inflammatory Response  Rebecca C.C. Brooke, Animesh Sinha, Meneka K. Sidhu, Rachel E.B. Watson, Martin K. Church, Peter S. Friedmann, Geraldine F. Clough, Lesley E. Rhodes  Journal of Investigative Dermatology  Volume 126, Issue 10, Pages 2296-2301 (October 2006) DOI: 10.1038/sj.jid.5700449 Copyright © 2006 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 1 Clinical illustration of the wheal and flare response to ALA-PDT. A 2% ALA solution was applied to 1cm diameter circular areas of healthy ventral forearm skin by iontophoresis, using a current of 0.2mA and charges of 3.8, 7.6, and 15mC, respectively. After 5hours, the sites were exposed to broadband red light, dose 100mJ/cm2, and application time 22minutes. A dose-related wheal and flare reaction was visible immediately post-irradiation, the erythemal reaction extending beyond the site of application of ALA-PDT. N=1. Journal of Investigative Dermatology 2006 126, 2296-2301DOI: (10.1038/sj.jid.5700449) Copyright © 2006 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 2 ALA-PDT induces an ALA dose-related immediate urticarial response in human skin. A geometric series of six ALA doses was iontophoresed into ventral forearm skin with a current of 0.2mA and an application time ranging from 19seconds to 10minutes, delivering a total charge of 3.8–120mC. After 5hours, sites were simultaneously exposed to 100J/cm2 red light. The areas of the (a) wheal and (b) flare responses were measured by planimetry immediately post-irradiation. N=6; results are means±SEM. Journal of Investigative Dermatology 2006 126, 2296-2301DOI: (10.1038/sj.jid.5700449) Copyright © 2006 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 3 ALA-PDT induces a prolonged ALA dose-related erythemal response. The erythemal response to ALA-PDT was quantified with a reflectance instrument at (a) 3hours and (b) 24hours following light exposure (N=6). A geometric series of six ALA doses was iontophoresed into ventral forearm skin with a current of 0.2mA and a total charge of 3.8–120mC. After 5hours, sites were simultaneously exposed to 100J/cm2 red light. At each site, the mean of three readings was taken and the erythema reading of adjacent untreated skin was subtracted. Results are means±SEM. Journal of Investigative Dermatology 2006 126, 2296-2301DOI: (10.1038/sj.jid.5700449) Copyright © 2006 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 4 H1 blockade reduces the immediate urticarial response to ALA-PDT. A geometric series of six ALA doses was iontophoresed into ventral forearm skin with a current of 0.2mA and an application time ranging from 19seconds to 10minutes, delivering a total charge of 3.8–120mC. After 5hours, sites were simultaneously exposed to 100J/cm2 red light. This experiment was repeated on contralateral forearm skin, while subjects were taking oral cetirizine 10mg daily. The (a) wheal and (b) flare areas were measured immediately post-irradiation. Solid symbols represent the baseline data and open symbols are the data obtained during H1 blockade. N=6; results are means±SEM. Journal of Investigative Dermatology 2006 126, 2296-2301DOI: (10.1038/sj.jid.5700449) Copyright © 2006 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 5 The prolonged erythemal response to ALA-PDT is unaffected by H1 blockade. A geometric series of six ALA doses was iontophoresed into ventral forearm skin with a current of 0.2mA and an application time ranging from 19seconds to 10minutes, delivering a total charge of 3.8–120mC. After 5hours, sites were simultaneously exposed to 100J/cm2 red light. This experiment was repeated on contralateral forearm skin, while subjects were taking oral cetirizine 10mg daily. Erythema was quantified at 3 and 24hours using a reflectance instrument, and the 24hour data are presented. Solid symbols represent baseline data and open symbols are data obtained during H1 blockade. N=6; results are means±SEM. Journal of Investigative Dermatology 2006 126, 2296-2301DOI: (10.1038/sj.jid.5700449) Copyright © 2006 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 6 Dermal histamine levels before, during, and following ALA-PDT. Topical ALA (20% in unguentum merck) was applied overnight at a density of 0.25g/cm2 to a 10 × 4cm area of the ventral forearm, and the site was exposed to 100J/cm2 red light after 16hours. Five microdialysis fibers (molecular mass cutoff 5kDa) were inserted under topical anesthesia, such that they lay parallel to each other at 1cm intervals. Four of the fibers were inserted before light exposure, whereas the fifth was inserted before collection of the final sample. A 2-hour recovery period was allowed before perfusion of the dialysis probes, performed using syringe pumps calibrated to run at 5μl/min. Ringer's solution with 5μg/ml noradrenaline was used as perfusate in order to maximize mediator recovery. The first 30minutes of dialysate was discarded. Dialysate was then collected over 30-minute periods on six occasions, that is, before irradiation (−0.5hours), during irradiation (0hours), immediately post-irradiation (0.5hours), and at 1, 4, and 24hours post-irradiation, except the 0-hour sample, which was collected over the 22-minute irradiation period. Microdialysate was centrifuged and stored at −80°C until analysis. Histamine levels were assayed using a proprietary ELISA kit. N=7; results are means±SEM. Journal of Investigative Dermatology 2006 126, 2296-2301DOI: (10.1038/sj.jid.5700449) Copyright © 2006 The Society for Investigative Dermatology, Inc Terms and Conditions