Journal of Photochemistry and Photobiology B-biology 

About: Journal of Photochemistry and Photobiology B-biology is an academic journal published by Elsevier BV. The journal publishes majorly in the area(s): Photodynamic therapy & Photosensitizer. It has an ISSN identifier of 1011-1344. Over the lifetime, 6091 publications have been published receiving 220733 citations.

The epidemiology of UV induced skin cancer.

Abstract: There is persuasive evidence that each of the three main types of skin cancer, basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma, is caused by sun exposure. The incidence rate of each is higher in fairer skinned, sun-sensitive rather than darker skinned, less sun-sensitive people; risk increases with increasing ambient solar radiation; the highest densities are on the most sun exposed parts of the body and the lowest on the least exposed; and they are associated in individuals with total (mainly SCC), occupational (mainly SCC) and non-occupational or recreational sun exposure (mainly melanoma and BCC) and a history of sunburn and presence of benign sun damage in the skin. That UV radiation specifically causes these skin cancers depends on indirect inferences from the action spectrum of solar radiation for skin cancer from studies in animals and the action spectrum for dipyrimidine dimers and evidence that presumed causative mutations for skin cancer arise most commonly at dipyrimidine sites. Sun protection is essential if skin cancer incidence is to be reduced. The epidemiological data suggest that in implementing sun protection an increase in intermittency of exposure should be avoided, that sun protection will have the greatest impact if achieved as early as possible in life and that it will probably have an impact later in life, especially in those who had high childhood exposure to solar radiation.

Photodynamic therapy with endogenous protoporphyrin IX: basic principles and present clinical experience.

Abstract: 5-Aminolaevulinic acid (ALA) is a precursor of protoporphyrin IX (Pp IX) in the biosynthetic pathway for haem. Certain types of cells have a large capacity to synthesize Pp IX when exposed to an adequate concentration of exogenous ALA. Since the conversion of Pp IX into haem is relatively slow, such cells tend to accumulate photosensitizing concentrations of Pp IX. Pp IX photosensitization can be induced in cells of the epidermis and its appendages, but not in the dermis. Moreover, since ALA in aqueous solution passes readily through abnormal keratin, but not through normal keratin, the topical application of ALA in aqueous solution to actinic keratoses or superficial basal cell or squamous cell carcinomas induces Pp IX photosensitization that is restricted primarily to the abnormal epithelium. Subsequent exposure to photoactivating light selectively destroys such lesions. In our ongoing clinical trial of ALA-induced Pp IX photodynamic therapy, the response rate for basal cell carcinomas following a single treatment has been 90% complete response and 7.5% partial response for the first 80 lesions treated. The cosmetic results have been excellent, and patient acceptance has been very good.

Endogenous protoporphyrin IX, a clinically useful photosensitizer for photodynamic therapy.

Abstract: The tissue photosensitizer protoporphyrin IX (PpIX) is an immediate precursor of heme in the biosynthetic pathway for heme. In certain types of cells and tissues, the rate of synthesis of PpIX is determined by the rate of synthesis of 5-aminolevulinic acid (ALA), which in turn is regulated via a feedback control mechanism governed by the concentration of free heme. The presence of exogenous ALA bypasses the feedback control, and thus may induce the intracellular accumulation of photosensitizing concentrations of PpIX. However, this occurs only in certain types of cells and tissues. The resulting tissue-specific photosensitization provides a basis for using ALA-induced PpIX for photodynamic therapy. The topical application of ALA to certain malignant and non-malignant lesions of the skin can induce a clinically useful degree of lesion-specific photosensitization. Superficial basal cell carcinomas showed a complete response rate of approximately 79% following a single exposure to light. Recent preclinical studies in experimental animals and human volunteers indicate that ALA can induce a localized tissue-specific photosensitization if administered by intradermal injection. A generalized but still quite tissue-specific photosensitization may be induced if ALA is administered by either subcutaneous or intraperitoneal injection or by mouth. This opens the possibility of using ALA-induced PpIX to treat tumors that are too thick or that lie too deep to be accessible to either topical or locally injected ALA.

Primary and secondary mechanisms of action of visible to near-IR radiation on cells.

Abstract: Cytochrome c oxidase is discussed as a possible photoacceptor when cells are irradiated with monochromatic red to near-IR radiation. Four primary action mechanisms are reviewed: changes in the redox properties of the respiratory chain components following photoexcitation of their electronic states, generation of singlet oxygen, localized transient heating of absorbing chromophores, and increased superoxide anion production with subsequent increase in concentration of the product of its dismutation, H2O2. A cascade of reactions connected with alteration in cellular homeostasis parameters (pHi, [Cai], cAMP, Eh, [ATP] and some others) is considered as a photosignal transduction and amplification chain in a cell (secondary mechanisms).

Can light absorption and photostability data be used to assess the photosafety risks in patients for a new drug molecule

Abstract: Photosafety assessments are recommended for all new drug candidates intended for clinical use. In 2002, Testing guidances were issued by the regulatory authorities in the USA (2003) and Europe (2002). A key requirement is to measure the absorption of UV-visible light by a compound in the 290-700 nm range and to assess photostability. Further photosafety evaluation is recommended for molecules which absorb light energy in this region and may be unstable in light. Consequently, the current guidances do not specify what constitutes a significant level of light absorbance or photoinstability. The current study was undertaken to determine the level of light absorption by measuring the molar extinction coefficients (MEC) of a wide range of compounds reported in the literature to have known photosafety issues in humans. The results have shown that all compounds tested have absorbance intensities significantly above an MEC threshold of 1000 L mol(-1)cm(-1) and also display a wide range of photoinstability. The measurement of light absorption is a contributing part of an overall pre-clinical photosafety risk assessment process, whereas photostability assessments have proven to have limited value. Molecules with an MEC less than 1000 L mol(-1)cm(-1)are deemed less of a photosafety risk since this low level of light absorption is unlikely to prove harmful.