Different types of porphyria are genetically caused by mutations in the enzymes of the haem synthetic pathway. Variegate porphyria, due to mutations in protoporphyrinogen oxidase (PPOX), causes acute visceral attacks and photosensitivity, presenting in blistering and fragile skin identical to porphyria cutanea tarda. This fragility and delayed healing are due to accumulation of porphyrins from the haem pathway, such as 5’-aminolevulenic acid (ALA), close to the skin surface that are oxidised by sunlight. Oxidised porphyrins can cause degranulation of mast cells resulting in the release of proteases that cause blistering. To elucidate whether a reduction of PPOX expression in keratinocytes themselves causes pathological changes we used shRNA to create two PPOX KD nTERT keratinocyte cell lines, one with 50% protein expression (KD1) and one with 25% remaining (KD2). Our results showed that, when untreated, both KDs grew significantly slower than shC but after treatment with ALA and DFO, an iron chelator that inhibits the production of haem, the growth rate of shC was reduced and no longer significantly greater than KD1. Migration was also reduced in KD2 but not KD1. ALAS1 expression was not altered with the reduction of PPOX but treatment with ALA ablated expression in all lines. Differentiation was also altered when untreated, with KD2 showing reduced KRT10 expression compared to shC, while treatment with ALA and DFO reduced KRT10 expression in shC. All cell lines form stratified epithelia in 3D organotypic cultures. Our results highlight a threshold of enzyme function that effects proliferation, migration, and differentiation, possibly due to levels of intermediate porphyrins that accumulate within the cells. This level of enzyme function is dependent on mutation and inheritance. We also show that keratinocytes have an active haem pathway, that can cause this porphyrin accumulation. We therefore show that reduction in PPOX expression causes changes to the keratinocytes themselves, that could have pathological effects, on top of blistering caused by UV damage due to excitation of porphyrins.

LB047 - More to porphyria than what lies beneath

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.