Radiation-induced erythema

Ultraviolet wavelengths of 290-310 nm from the UV-B band of radiation constitute the principal tissue-damaging rays of the sun, which are not fully atmospherically filtered. An hour s exposure to the summer sun and its damaging rays can produce a painful burn with a characteristic erythema. The skin has natural mechanisms to prevent or minimize such sun-induced trauma, but it takes time to set these into place. Upon... 

DNA strongly absorbs UV radiation, especially mid-range UVB (290 to 320 nm) radiation. Two major DNA lesions are induced following UV exposure, pyrimidine dimers and 6-4 pyrimidine-pyrimidone photoproducts. Because the action spectrum (induction of a biological activity as a function of wavelength) for erythema closely matches the action spectrum for pyrimidine dimer formation, DNA is believed to be the chromophore for sunburn.6 Pyrimidine dimer formation, or more properly, the failure to adequately repair dimers after solar irradiation is also the primary cause of sunlight-induced skin cancer formation.7-8... 

McKinlay, A. F., and Diffey, B. L. (1987) A reference action spectrum for ultraviolet induced erythema in human skin, in W. F. Passchier and B. F. M. Bosnajakovic (eds.). Human Exposure to Ultraviolet Radiation Risks and Regulations, Elsevier, New York, pp. 83-87. 

The main dose-limiting toxicity of all anthracyclines is myelosuppression, with neutropenia more commonly observed than thrombocytopenia. In some cases, mucositis is dose-limiting. Two forms of cardiotoxicity are observed. The acute form occurs within the first 2-3 days and presents as arrhythmias or conduction abnormalities, other electrocardiographic changes, pericarditis, and myocarditis. This form is usually transient and is asymptomatic in most cases. The chronic form results in a dose-dependent, dilated cardiomyopathy associated with heart failure. The chronic cardiac toxicity appears to result from increased production of free radicals within the myocardium. This effect is rarely seen at total doxorubicin dosages below 500-550 mg/m2. Use of lower weekly doses or continuous infusions of doxorubicin appear to reduce the incidence of cardiac toxicity. In addition, treatment with the iron-chelating agent dexrazoxane (ICRF-187) is currently approved to prevent or reduce anthracycline-induced cardiotoxicity in women with metastatic breast cancer who have received a total cumulative dose of doxorubicin of 300 mg/m2. All anthracyclines can produce "radiation recall reaction," with erythema and desquamation of the skin observed at sites of prior radiation therapy. 

Mutscheller 1/100 of the radiation dose which induces the erythema Tolerance dose... 

Erythema is the most common effect of UVR exposure. The exact mechanism of how UVR induces skin erythema is not fully understood however, it is believed that a number of mediators are involved in the inflammatory reaction (260). These include histamine, lysosomal enzymes, kinins, and at least one prostaglandin. These mediators produce vasodilatation, which is manifested in erythema. As the UV radiation penetrates into the epidermis, another inflammatory reaction involving a lymphocytic infiltrate develops. Swelling of the endothelium and leakage of red blood cells also occurs. The inflammatory effect of UVB radiation reaches its maximum in 12-24 h after exposure (260). 

The search for new and effective treatment modalities requires the availability of adequate screening tests. Although no model adequately reflects the events that occur in human arthritic conditions, several in vivo and in vitro assays are used. The most common in vivo animal assays measure the ability of anti-inflammatory drugs to inhibit edema induced in the rat paw by carrageenan (a mucopolysaccharide derived from a sea moss of the Chondrus species), to inhibit adjuvant arthritis in rats induced by Mycobacterium butyricum or M. tuberculosis, to inhibit granuloma formation usually induced by the implantation of a cotton pellet beneath the abdominal skin of rats, or to inhibit erythema of guinea pig skin as a result of exposure to ultraviolet radiation. In vitro techniques include the ability of NSAIDs to stabilize erythrocyte membranes or, more commonly, to inhibit the biosynthesis of prostaglandins, particularly in cultured human synoviocytes and chondrocytes, and monocyte culture fluid stimulated bovine synoviocytes and chondrocytes. 

Schempp, C.M., B. Winghofer, K. Muller, et al. 2003. Effect of oral administration of Hypericum perforatum extract (St. John s wort) on skin erythema and pigmentation induced by UVB, UVA, visible light and solar simulated radiation. Phytother. Res. 17(2) 141-146.

The dose of radiation used in photo-patch testing varies between 1 J/cm and 10 J/cm in most studies. Theoretically, the largest dose that does not alone induce erythema in skin would be most likely to yield production of the photoantigen and a positive test response. Since the minimal erythema dose (MED) in... 

The potential topical anti-in ammatory activity of Coriandrum sativum essential oil has been investigated in human subjects. Using a monocentric, double-blind trial, erythema was initiated on the backs of 40 volunteers using ultraviolet B (UVB) radiation. The test areas were subsequently treated under occlusion with a lipolotion containing 0.5% or 1% coriander essential oil for 47 h. Betamethasone valerate and hydrocortisone were used as controls, with the vehicle alone as a placebo. The erythema was measured photometrically after 48 h. The 0.5% coriander essential oil signi cantly reduced the UV-induced erythema in comparison to the placebo but was not as effective as hydrocortisone. A mild anti-in ammatory effect was thus demonstrated that could be used in the concomitant treatment of in ammatory skin diseases (Reuter et al., 2008). 

UV induced erythema refers to the skin becoming red due to hyperemia of the capillaries in the lower layers of the skin induced by solar radiation (coimnonly called sunburns). In severe cases, blistering and peeling of the skin can occur. One randomized, double-blind, placebo-controlled trial (Reuter et al., 2008) compared the anti-inflaimnatory effect of 97.5% pure Aloe vera gel to 1% hydrocortisone and a placebo gel and concluded that if Aloe vera gel is applied under an occlusive bandage for 2 days following UV exposure, inflammation is... 

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