Evidence and conjecture about mechanisms of cutaneous disease in photodermatology

Unleashing the power of porphyrin photosensitizers: Illuminating breakthroughs in photodynamic therapy

This comprehensive review provides the current trends and recent developments of porphyrin-based photosensitizers. We discuss their evolution from first-generation to third-generation compounds, including cutting-edge nanoparticle-integrated derivatives, and explores their pivotal role in advancing photodynamic therapy (PDT) for enhanced cancer treatment. Integrating porphyrins with nanoparticles represents a promising avenue, offering improved selectivity, reduced toxicity, and heightened biocompatibility. By elucidating recent breakthroughs, innovative methodologies, and emerging applications, this review provides a panoramic snapshot of the dynamic field, addressing challenges and charting prospects. With a focus on harnessing reactive oxygen species (ROS) through light activation, PDT serves as a minimally invasive therapeutic approach. This article offers a valuable resource for researchers, clinicians, and PDT enthusiasts, highlighting the potential of porphyrin photosensitizers to improve the future of cancer therapy.

NRF2 in dermatological disorders: Pharmacological activation for protection against cutaneous photodamage and photodermatosis

The skin barrier and its endogenous protective mechanisms cope daily with exogenous stressors, of which ultraviolet radiation (UVR) poses an imminent danger. Although the skin is able to reduce the potential damage, there is a need for comprehensive strategies for protection. This is particularly important when developing pharmacological approaches to protect against photocarcinogenesis. Activation of NRF2 has the potential to provide comprehensive and long-lasting protection due to the upregulation of numerous cytoprotective downstream effector proteins that can counteract the damaging effects of UVR. This is also applicable to photodermatosis conditions that exacerbate the damage caused by UVR. This review describes the alterations caused by UVR in normal skin and photosensitive disorders, and provides evidence to support the development of NRF2 activators as pharmacological treatments. Key natural and synthetic activators with photoprotective properties are summarized. Lastly, the gap in knowledge in research associated with photodermatosis conditions is highlighted.

Liver involvement in patients with erythropoietic protoporphyria

BACKGROUND

In erythropoietic protoporphyria (EPP), which presents with severe painful phototoxicity, progressive deposition of protoporphyrins in hepatocytes and bile canaliculi may result in liver disease. Clinically EPP related liver disease ranges from mildly elevated liver enzymes to cirrhosis and acute cholestatic hepatic failure. The prevalence of liver disease in EPP, and factors predicting the risk of developing liver disease, have not been defined in a large series of unselected EPP patients.

AIM

To determine the prevalence of liver disease in EPP-patients.

METHODS

A single-center prospective unselected cohort study of 114 adult EPP patients, who underwent routine laboratory testing, abdominal ultrasonography and transient elastography to assess the presence of steatosis (controlled attenuation parameter,dB/m) and liver stiffness (kPa).

RESULTS

114 adult EPP patients were included. Elevated liver enzymes were found in 6.2% of the patients. Liver steatosis was detected in 29.0%, and significant fibrosis as assessed with liver stiffness measurements was present in 9.6% of patients. BMI positively predicted CAP-values (p = 0.026); and protoporphyrin IX levels (p = 0.043) positively predicted liver stiffness.

CONCLUSIONS

This study demonstrates a prevalence of hepatic steatosis and fibrosis in adult EPP-patients comparable to that found in the general population. Protoporphyrin IX levels correlate with increased liver stiffness in EPP.

Objective light exposure measurements and circadian rhythm in patients with erythropoietic protoporphyria: A case-control study

BACKGROUND

Erythropoietic protoporphyria (EPP) patients suffer from painful phototoxicity. Sunlight-avoiding behaviour has not yet been quantified objectively in EPP patients.

OBJECTIVE

To study total white light exposure obtained with an actigraph device, before and during afamelanotide treatment, in EPP patients compared to healthy controls. Effects on circadian rhythm, pain and sleep were also investigated.

METHODS

Adult EPP patients visiting the Porphyria Center Rotterdam of the Erasmus MC were included in this single-center longitudinal case-control open-label intervention study. Controls were age and place of residence matched. Participants wore an actigraph (Actiwatch Pro) during two weeks for multiple periods. Afamelanotide was given to EPP patients as part of standard care.

RESULTS

Twenty-six EPP patients and 23 matched controls participated. Controls were statistically significantly more exposed to white light than EPP patients off treatment during autumn (95.4%), spring (69.9%), and summer (105.4%; p = 0.01). EPP patients on afamelanotide treatment had 71.6% more light exposure during spring compared to EPP patients off treatment (p < 0.01). Afamelanotide treatment resulted in a reduction of painful moments in the morning (6.5% decrease) and the evening (8.1% decrease; p < 0.05). Bedtime differed between EPP patients off treatment, controls and EPP patients on treatment (23:45 h ± 1:51 versus 23:02 ± 1:41 and 23:14 ± 1:29, respectively; p < 0.0001).

CONCLUSION

Actigraphy is a useful method to objectively measure white light exposure and treatment effects in EPP. In EPP patients afamelanotide treatment is associated with increased white light exposure during spring, and overall less pain. Treatment with afamelanotide is also associated with normalization of circadian rhythm.

Afamelanotide for prevention of phototoxicity in erythropoietic protoporphyria

Introduction: In erythropoietic protoporphyria (EPP), an inherited disorder of heme biosynthesis, accumulation of protoporphyrin IX results in acute phototoxicity. EPP patients experience severe burning pain after light exposure, which results in a markedly reduced quality of life. Afamelanotide is the first effective approved medical treatment for EPP, acting on melanocortin-1 receptors. This article aims to review afamelanotide.Areas covered: This review summarizes the chemical properties, pharmacokinetics, safety, preclinical and clinical data on afamelanotide in EPP, and post-marketing surveillance. PubMed search, manufacturers' websites, and relevant articles used for approval by authorities were used for the literature search.Expert opinion: Afamelanotide is an α-melanocyte-stimulating hormone analog. It can activate eumelanogenesis without exposure to UV radiation. Clinical studies in EPP showed that afamelanotide treatment significantly increased exposure to sunlight and QoL. In our clinical experience afamelanotide treatment is much more effective in clinical practice than demonstrated in clinical trials and should be made available for all EPP patients meeting inclusion criteria. The 60-day interval period was not based on effectiveness studies, and therefore for some of the patients the maximum of four implants per year with the 60-day interval is insufficient. Afamelanotide is well tolerated; common adverse events were headache, fatigue, and nausea.

Association of Afamelanotide With Improved Outcomes in Patients With Erythropoietic Protoporphyria in Clinical Practice

Importance

The effectiveness of afamelanotide treatment in patients with erythropoietic protoporphyria (EPP) in clinical practice who experience pain after light exposure that substantially impairs quality of life is unknown.

Objective

To evaluate the association of afamelanotide treatment with outcomes in patients with EPP in regular practice during longer-term follow-up.

Design, Setting, and Participants

This single-center, prospective postauthorization safety and efficacy cohort study was directed and approved by the European Medicines Agency. Data were collected from patients with EPP treated with afamelanotide at Erasmus MC between June 2016 and September 2018. Analysis began October 2018.

Main Outcomes and Measures

Time spent outside during treatment, number of phototoxic reactions, disease-specific quality of life, usage of protective clothing, and adverse events.

Results

A total of 117 patients with EPP (59 women [50.4%]; mean [SD] age, 43.0 [15.5] years) were treated with afamelanotide. Nearly all patients continued treatment (115 [98%]) with a median (interquartile range) follow-up of 2.0 (1.3-2.1) years. Compared with baseline, mean time spent outside during treatment increased significantly by an added 6.1 hours per week (95% CI, 3.62-8.67; P < .001). Mean quality of life score improved significantly by 14.01% (95% CI, 4.53%-23.50%; P < .001). Phototoxic reactions were less painful (β, -0.85; 95% CI, -1.43 to -0.26; P < .001), but there was no significant difference in number or duration of reactions. Minor self-limiting adverse events occurred, such as nausea, fatigue, and headache.

Conclusions and Relevance

This cohort study found that afamelanotide treatment was associated with improved clinical outcomes and a good safety profile for patients with EPP. The treatment has clinically significant, sustained positive associations with quality of life, is associated with increased duration of sun exposure, and is associated with less severe phototoxic reactions.

Oxygen and Conformation Dependent Protein Oxidation and Aggregation by Porphyrins in Hepatocytes and Light-Exposed Cells

BACKGROUND & AIMS

Porphyrias are caused by porphyrin accumulation resulting from defects in the heme biosynthetic pathway that typically lead to photosensitivity and possible end-stage liver disease with an increased risk of hepatocellular carcinoma. Our aims were to study the mechanism of porphyrin-induced cell damage and protein aggregation, including liver injury, where light exposure is absent.

METHODS

Porphyria was induced in vivo in mice using 3,5-diethoxycarbonyl-1,4-dihydrocollidine or in vitro by exposing human liver Huh7 cells and keratinocytes, or their lysates, to protoporphyrin-IX, other porphyrins, or to δ-aminolevulinic acid plus deferoxamine. The livers, cultured cells, or porphyrin exposed purified proteins were analyzed for protein aggregation and oxidation using immunoblotting, mass spectrometry, and electron paramagnetic resonance spectroscopy. Consequences on cell-cycle progression were assessed.

RESULTS

Porphyrin-mediated protein aggregation required porphyrin-photosensitized singlet oxygen and porphyrin carboxylate side-chain deprotonation, and occurred with site-selective native protein methionine oxidation. Noncovalent interaction of protoporphyrin-IX with oxidized proteins led to protein aggregation that was reversed by incubation with acidified n-butanol or high-salt buffer. Phototoxicity and the ensuing proteotoxicity, mimicking porphyria photosensitivity conditions, were validated in cultured keratinocytes. Protoporphyrin-IX inhibited proteasome function by aggregating several proteasomal subunits, and caused cell growth arrest and aggregation of key cell proliferation proteins. Light-independent synergy of protein aggregation was observed when porphyrin was applied together with glucose oxidase as a secondary peroxide source.

CONCLUSIONS

Photo-excitable porphyrins with deprotonated carboxylates mediate protein aggregation. Porphyrin-mediated proteotoxicity in the absence of light, as in the liver, requires porphyrin accumulation coupled with a second tissue oxidative injury. These findings provide a potential mechanism for internal organ damage and photosensitivity in porphyrias.

Human health in relation to exposure to solar ultraviolet radiation under changing stratospheric ozone and climate

The Montreal Protocol has limited increases in the UV-B (280-315 nm) radiation reaching the Earth's surface as a result of depletion of stratospheric ozone. Nevertheless, the incidence of skin cancers continues to increase in most light-skinned populations, probably due mainly to risky sun exposure behaviour. In locations with strong sun protection programs of long duration, incidence is now reducing in younger age groups. Changes in the epidemiology of UV-induced eye diseases are less clear, due to a lack of data. Exposure to UV radiation plays a role in the development of cataracts, pterygium and possibly age-related macular degeneration; these are major causes of visual impairment world-wide. Photodermatoses and phototoxic reactions to drugs are not uncommon; management of the latter includes recognition of the risks by the prescribing physician. Exposure to UV radiation has benefits for health through the production of vitamin D in the skin and modulation of immune function. The latter has benefits for skin diseases such as psoriasis and possibly for systemic autoimmune diseases such as multiple sclerosis. The health risks of sun exposure can be mitigated through appropriate sun protection, such as clothing with both good UV-blocking characteristics and adequate skin coverage, sunglasses, shade, and sunscreen. New sunscreen preparations provide protection against a broader spectrum of solar radiation, but it is not clear that this has benefits for health. Gaps in knowledge make it difficult to derive evidence-based sun protection advice that balances the risks and benefits of sun exposure.

Comparative Metabolomic Profiling Reveals That Dysregulated Glycolysis Stemming from Lack of Salvage NAD+ Biosynthesis Impairs Reproductive Development in Caenorhabditis elegans

Temporal developmental progression is highly coordinated in Caenorhabditis elegans. However, loss of nicotinamidase PNC-1 activity slows reproductive development, uncoupling it from its typical progression relative to the soma. Using LC/MS we demonstrate that pnc-1 mutants do not salvage the nicotinamide released by NAD(+) consumers to resynthesize NAD(+), resulting in a reduction in global NAD(+) bioavailability. We manipulate NAD(+) levels to demonstrate that a minor deficit in NAD(+) availability is incompatible with a normal pace of gonad development. The NAD(+) deficit compromises NAD(+) consumer activity, but we surprisingly found no functional link between consumer activity and reproductive development. As a result we turned to a comparative metabolomics approach to identify the cause of the developmental phenotype. We reveal widespread metabolic perturbations, and using complementary pharmacological and genetic approaches, we demonstrate that a glycolytic block accounts for the slow pace of reproductive development. Interestingly, mitochondria are protected from both the deficiency in NAD(+) biosynthesis and the effects of reduced glycolytic output. We suggest that compensatory metabolic processes that maintain mitochondrial activity in the absence of efficient glycolysis are incompatible with the requirements for reproductive development, which requires high levels of cell division. In addition to demonstrating metabolic requirements for reproductive development, this work also has implications for understanding the mechanisms behind therapeutic interventions that target NAD(+) salvage biosynthesis for the purposes of inhibiting tumor growth.

Afamelanotide for Erythropoietic Protoporphyria

BACKGROUND

Erythropoietic protoporphyria is a severe photodermatosis that is associated with acute phototoxicity. Patients with this condition have excruciating pain and a markedly reduced quality of life. We evaluated the safety and efficacy of an α-melanocyte-stimulating hormone analogue, afamelanotide, to decrease pain and improve quality of life.

METHODS

We conducted two multicenter, randomized, double-blind, placebo-controlled trials of subcutaneous implants containing 16 mg of afamelanotide. Patients in the European Union (74 patients) and the United States (94 patients) were randomly assigned, in a 1:1 ratio, to receive a subcutaneous implant containing either afamelanotide or placebo every 60 days (a total of five implants in the European Union study and three in the U.S study). The type and duration of sun exposure, number and severity of phototoxic reactions, and adverse events were recorded over the respective 180-day and 270-day study periods. Quality of life was assessed with the use of validated questionnaires. A subgroup of U.S. patients underwent photoprovocation testing. The primary efficacy end point was the number of hours of direct exposure to sunlight without pain.

RESULTS

In the U.S. study, the duration of pain-free time after 6 months was longer in the afamelanotide group (median, 69.4 hours, vs. 40.8 hours in the placebo group; P=0.04). In the European Union study, the duration of pain-free time after 9 months was also longer in the afamelanotide group than in the placebo group (median, 6.0 hours vs. 0.8 hours; P=0.005), and the number of phototoxic reactions was lower in the the afamelanotide group (77 vs. 146, P=0.04). In both trials, quality of life improved with afamelanotide therapy. Adverse events were mostly mild; serious adverse events were not thought to be related to the study drug.

CONCLUSIONS

Afamelanotide had an acceptable side-effect and adverse-event profile and was associated with an increased duration of sun exposure without pain and improved quality of life in patients with erythropoietic protoporphyria. (Funded by Clinuvel Pharmaceuticals and others; ClinicalTrials.gov numbers, NCT01605136 and NCT00979745.).