R.K. Hans

Photosensitizing Potential of Ciprofloxacin at Ambient Level of UV Radiation

Ciprofloxacin is a widely used fluoroquinolone drug with broad spectrum antibacterial activities. Clinical experience has shown incidences of adverse effects related to skin, hepatic, central nervous system, gastrointestinal and phototoxicity. India is a tropical country and sunlight is abundant throughout the day. In this scenario exposure to ambient levels of ultraviolet radiation (UV‐R) in sunlight may lead to harmful effects in ciprofloxacin users. Phototoxicity assessment of ciprofloxacin was studied by two mouse fibroblast cell lines L‐929 and NIH‐3T3. Generation of reactive oxygen species (ROS) like singlet oxygen (1O2), superoxide anion radical (O2ḃ−) and hydroxyl radical (ḃOH) was studied under the exposure of ambient intensities of UV‐A (1.14, 1.6 and 2.2 mW cm−2), UV‐B (0.6, 0.9 and 1.2 mW cm−2) and sunlight (60 min). The drug was generating 1O2, O2ḃ− and ḃOH in a concentration and dose‐dependent manner. Sodium azide (NaN3) and 1,4‐diazabicyclo 2‐2‐2‐octane (DABCO) inhibited the generation of 1O2. Superoxide dismutase (SOD) inhibited 90–95% O2ḃ− generation. The drug (5–40 μg mL−1) was responsible for linoleic acid peroxidation. Quenching study of linoleic acid peroxidation with SOD (25 and 50 U mL−1) confirms the involvement of ROS in drug‐induced lipid peroxidation. The generation of ḃOH radical was further confirmed by using specific quenchers of ḃOH such as mannitol (0.5 m) and sodium benzoate (0.5 m). 2′‐deoxyguanosine (2′‐dGuO) assay and linoleic acid peroxidation showed that ROS were mainly responsible for ciprofloxacin‐sensitized photo‐degradation of guanine base. L‐929 cell line showed 29%, 34% and 54% reduced cell viability at higher drug concentration (300 μg mL−1) under UV‐A, UV‐B and sunlight, respectively. 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide (MTT) assay in NIH‐3T3 cell line at higher drug concentration (300 μg mL−1) showed a decrease in cell viability by 54%, 56% and 59% under UV‐A, UV‐B and sunlight, respectively. Results of neutral red uptake assay (NRU) in L‐929 cell line were in accordance with MTT assay. The NIH‐3T3 cell line showed a higher photosensitizing potential than L‐929. The phototoxicity end point shows a time‐ and concentration‐dependent statistically significant (P < 0.001) damage. Ciprofloxacin produced ROS by Type I and Type II photodynamic reactions, interacted with nucleic acid moiety and inhibited cell viability. Further, UV‐induced photo‐peroxidation of linoleic acid accorded the involvement of ROS in the manifestation of drug phototoxicity. Appearance of ciprofloxacin‐induced phototoxicity at the ambient level of sunlight is a real risk for the people of India and for those of other tropical countries. We suggest that sunlight exposure should be avoided (especially peak hours) during ciprofloxacin treatment.

DDT and HCH Residues in Basmati Rice (Oryza sativa) Cultivated in Dehradun (India)

Organochlorine pesticides were used earlier for agricultureproduction. Their residues may still be present in soil and mayaccumulate in food crops, posing potential health problems to consumers. DDT, HCH, their isomers and metabolites were analyzedin samples of soil and rice plants collected from ten differentvillages of a well-known Basmati rice growing area in Dehradun.Residues of both pesticides were found in all samples ofsoil and different parts of rice plants except for a few grainsamples. Maximum residue was observed in husk and minimum ingrains. The average concentration of DDT in soil ranged from0.013 to 0.238 ppm. p,p′-DDE was the major metabolite (>63%). Theaverage concentration of DDT in rice grain varied from 0.002 to 0.040 ppm. o,p′-DDT was the main isomer (>93%). Theaverage concentration of HCH in soil ranged from 0.122 to 0.638 ppm. β-HCH was the predominant (43%) isomerfollowed by α-HCH (21%). The average HCH concentrationin rice grain ranged between 0.013 and 0.113 ppm. All four isomers were present in grains. The levels of DDT and CHCin grains were similar in magnitude as those from differentIndian states, but well below the maximum residue limit of 0.1 ppm for DDT and 0.05 ppm for HCH prescribed by the Government ofIndia and WHO/FAO. As such, the pesticide residue levels in thisexport commodity are not of hazardous nature.

Glutathione-S-transferase activity in an earthworm (Pheretima posthuma) exposed to three insecticides

Abstract The activity of glutathione-S-transferase (GST) was studied in earthworms exposed to l μg g−1 of aldrin, endosulphan or lindane for 1, 2 or 4 weeks in a potted soil test. The enhancement of GST activity was maximum after 1 week of exposure to the insecticides. After 2 weeks only aldrin and lindane caused significant increases. While after 4 weeks GST activity declined to near the control values in the presence of any one of three insecticides. Changes in enzyme may be related to the biotransformation and elimination of the pesticides.

Radiation-Induced in Vitro Phototoxic Potential of Some Fluoroquinolones

Photosensitizing drugs that can damage cellular biomolecules is a matter of concern. Lomefloxacin, norfloxacin, ofloxacin, and enoxacin (broad-spectrum antibiotics of fluoroquinolone group) are used for the treatment of Gram-positive and Gram-negative bacterial infections. Phototoxicity and possible mechanism of their action was assessed under the exposure of ambient levels of UV-A, UV-B, and sunlight at a concentration generally used in the treatment of various diseases. Singlet oxygen (1O2), superoxide anion radical (O2·−) generation, DNA damage, and lipid peroxidation in human blood were studied. All the fluoroquinolones tested in this study produced 1O2 and O2·− under exposure to UV-A, UV-B, and sunlight depending on the concentrations (0 to 60 μg/mL) of the drugs. Enoxacin showed a higher yield of 1O2 and O2·− than other drugs. These materials also degraded deoxyguanosine and induced lipid peroxidation in vitro under exposure to UV-A, UV-B, and sunlight (depending on the dose of radiation). The formation of the reactive oxygen species (ROS) by the photoexcited drugs may be considered as a possible mechanism of their action.

Effect of UV-B radiation on some common antibiotics.

Some of the commonly used antibiotics such as cephaloridine, cephalexin, cephradine, nystatin and nafcillin were tested for generation of singlet oxygen (1O(2)) under UV-B (290-320 nm) exposure and the order for 1O(2) generation was obtained: cephaloridine>cephalexin>nystatin>cephradine>nafcillin. In vitro study with deoxyguanosine (dGuo) showed that 1O(2) was responsible for drug-sensitized photodegradation of the guanine base of DNA and RNA. Sodium azide (NaN(3)) and 1,4-diazabicyclo [2.2.2] octane (DABCO) accorded significant inhibition (76-98%) in the production of (1)O(2) and photo-oxidation of dGuo. The combined effect of drug and UV-B irradiation is of paramount importance in view of cell-damaging reactions by 1O(2). Our findings are important because of increasing UV-B radiation on the earths surface due to depletion of the stratospheric ozone layer. The selected drugs are used routinely for the treatment of various diseases and their combined action may cause undesirable phototoxic responses. Our study suggests that exposure to sunlight should be avoided after the intake of the photosensitive drugs.

EVALUATION OF UV-INDUCED SUPEROXIDE RADICAL GENERATION POTENTIAL OF SOME COMMON ANTIBIOTICS

Photosensitization reaction of drugs leading to the formation of reactive oxygen species (ROS) cause tissue injury causing damage to various cellular macromolecules. The aim of this study was to determine the superoxide anion (O2−) generation potential of commonly used antibiotics so that due precaution could be exercised to minimize their photosensitizing action and oxidative stress potential. The selected antibiotics were examined for their ability to produce (O2−) under sunlight and artificial UVA (320–400 nm) and UVB (290–320 nm). Lincomycin, cephalothin and erythromycin generated significant amount of O2−. under various irradiation conditions. Superoxide dismutase (SOD), an enzymatic quencher of O2− inhibited O2− production in all drugs tested. The results suggest that due precaution are necessary to avoid ultraviolet radiation (UVR) after the intake of photoreactive drugs, especially in tropical and sub tropical countries.

Assessment of the phototoxic potential of cosmetic products

The cosmetics are nontoxic or less toxic in perse but photoactivation may then sensitize and could produce additional phototoxicity. Phototoxicity assessment of ten different lipsticks and eight facial creams was conducted. Results revealed that six lipsticks and five facial creams generated reactive oxygen species (ROS), produced haemolysis and caused lipid peroxidation in human erythrocytes (in vitro) under sunlight exposure. Seven creams and one lipstick were alkaline while one cream and two lipsticks were acidic. The test lipsticks and creams showed absorption in UV/visible range. The study demonstrated synergistic action of cosmetic products and sunlight. Therefore, sunlight exposure should be avoided after the use of photosensitive cosmetics.

An unusual photohaemolytic property of riboflavin

Riboflavin (RF) is a known photoreactive and phototoxic molecule. However, unlike other photosensitizers, it does not induce photohaemolysis of erythrocytes by itself. On the other hand, illuminated RF caused haemolysis but in the presence of serum or plasma. The kinetics of photohaemolysis in the presence of serum/plasma has been studied by monitoring the rate of haemolysis spectrophotometrically and morphological changes at erythrocytes membrane by scanning electron microscopy. We found that the extent of mammalian RBC membrane damage was dependent on the concentration of RF or hematoporphyrin (HP) (0-20 microgram/ml) and dose of sunlight (0-20 min). The RBC membrane-damaging potential of illuminated HP was not affected by the presence of plasma in the reaction system. Furthermore, RF showed a protective role against photohaemolysis caused by photoexcited HP if erythrocytes were preincubated with RF in the absence of serum/plasma. For mechanistic studies, biochemical parameters such as acetylcholinesterase activity (AChE) and formation of TBA-reactive substance (TBA-RS) were analysed in RBC and RBC+plasma under a similar set of experimental conditions. We observed about a 25% decrease in AchE activity as a synergistic action of RF or HP (20 microgram/ml) and sunlight (30 min) in both cases (RBC or RBC+plasma). Interestingly, illuminated RF caused about a 125% increase of TBA-RS in a reaction system consisting of RBC+plasma. On the other hand, an increase in the production of TBA-RS by illuminated RF was not observed in the absence of plasma/serum, in the reaction system. These results suggested that photooxidation of RBC membrane lipids by illuminated RF, under the influence of plasma/serum, may be one of the causes of membrane modification leading to RBC lysis.

EVALUATION OF UV-RADIATION INDUCED SINGLET OXYGEN GENERATION POTENTIAL OF SELECTED DRUGS

ABSTRACT Photosensitization reaction of drugs leading to the formation of reactive oxygen species under ultraviolet radiation (UVR) can cause tissue injury, resulting in damage to various cellular macromolecules. The aim of this study was to determine the singlet oxygen generation potential of some commonly used antibiotics so that due precautions can be exercised to minimize their photosensitizing action and oxidative stress potential. The selected antibiotics were examined for their ability to produce singlet oxygen (1O2) under artificial UVA (320–400 nm). Singlet oxygen generation of various screened antibiotics under UVA is of the follow-ing order : Nalidixic acid>Amphotericin-B>Cephradine>Cefazolin> Nafcillin>Cephalothin>Ampicillin>Cephalexin>Puromycin>Kanamycin>Lincomycin>Tetracycline>Nystatin>Gentamicin sulphate. Nalidixic acid, the most potent generator of 1O2 among the screened antibiotics, was selected to carry out further studies. Certain specific quenchers of 1O2 such as β-carotene, 1,4-diazabicyclo[2.2.2] octane (DABCO), and sodium azide (NaN3) accorded significant inhibition in the production of 1O2. The results suggest that precautions are necessary to avoid ultraviolet radiation after the intake of photoreactive drugs, especially in tropical countries such as India. These findings are significant because UVB radiation is reportedly increasing on earth surface in part due to depletion of stratospheric ozone layer. The selected drugs are commonly used for the treatment of various diseases. Thus, the synergistic action of both can lead to undesirable phototoxic responses.

Identification of new photoreduction products of pentachlorophenol

Pentachlorophenol (PCP), a fungicide and insecticide, leaves behind considerable residue in the environment in the form of unreacted molecule, metabolites and photoreduction products. Most of the previously reported photoproducts have resulted from dechlorination of the parent molecule. We have shown that photoreduction of PCP also proceeds by photoreduction of the parent molecule at carbons 2 and 4. These products were identified and characterized as 2-dehydro-2,3,4,5,6-pentachlorocyclohexanone (II) and 2,3,4,5,6-pentachlorocyclohexanone (IV). Both of them display keto-enol tautomerism. Identification and characterization of new photoproducts of PCP is significant for determining its overall environmental impact in the ecosystem.