Apoptosis mechanisms related to the increased sensitivity of Jurkat T-cells vs A431 epidermoid cells to photodynamic therapy with the phthalocyanine Pc 4

To examine the clinical applicability of Pc 4, a promising second-generation photosensitizer, for the photodynamic treatment of lymphocyte-mediated skin diseases, we studied the A431 and Jurkat cell lines, commonly used as surrogates for human keratinocyte-derived carcinomas and lymphocytes, respectively. As revealed by ethyl acetate extraction and absorption spectrophotometry, uptake of Pc 4 into the two cell lines was linear with Pc 4 concentration and similar on a per cell basis but greater in Jurkat cells on a per mass basis. Flow cytometry showed that uptake was linear at low doses; variations in the dose-response for uptake measured by fluorescence supported differential aggregation of Pc 4 in the two cell types. As detected by confocal microscopy, Pc 4 localized to mitochondria and endoplasmic reticulum in both cell lines. Jurkat cells were much more sensitive to the lethal effects of phthalocyanine photodynamic therapy (Pc 4-PDT) than were A431 cells, as measured by a tetrazolium dye reduction assay, and more readily underwent morphological apoptosis. In a search for molecular factors to explain the greater photosensitivity of Jurkat cells, the fate of important Bcl-2 family members was monitored. Jurkat cells were more sensitive to the induction of immediate photodamage to Bcl-2, but the difference was insufficient to account fully for their greater sensitivity. The antiapoptotic protein Mcl-1 was extensively cleaved in a dose- and caspase-dependent manner in Jurkat, but not in A431, cells exposed to Pc 4-PDT. Thus, the greater killing by Pc 4-PDT in Jurkat compared with A431 cells correlated with greater Bcl-2 photodamage and more strongly to the more extensive Mcl-1 degradation. Pc 4-PDT may offer therapeutic advantages in targeting inflammatory cells over normal keratinocytes in the treatment of T-cell-mediated skin diseases, such as cutaneous lymphomas, dermatitis, lichenoid tissue reactions and psoriasis, and it will be instructive to evaluate the role of Bcl-2 family proteins, especially Mcl-1, in the therapeutic response.     

Pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine Sulfonamides as Novel Potential Anticancer Agents: Cytotoxic and Genotoxic Activities In Vitro

In this paper, we present for the first time the evaluation of cytotoxicity and genotoxicity of de novo synthesized pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine sulfonamides MM129, MM130, and MM131 in human tumor cell lines: HeLa, HCT 116, PC-3, and BxPC-3. Cytotoxic and genotoxic properties of the tested compounds were estimated using the MTT assay, comet assay (alkaline and neutral version), and γ-H2AX immuno-staining. Examined sulfonamides exhibited strong anticancer properties towards tested cells in a very low concentration range (IC₅₀ = 0.17–1.15 μM) after 72 h exposure time. The results of the alkaline and neutral version of the comet assay following 24 h incubation of the cells with tested compounds demonstrated the capability of heterocycles to induce significant DNA damage in exposed cells. HCT 116 cells were the most sensitive to the genotoxic activity of novel tricyclic pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine sulfonamides in the neutral version of the comet assay. Immunocytochemical detection of γ-H2AX showed an increase in DNA DSBs level in the HCT 116 cell line, after 24 h incubation with all tested compounds, confirming the results obtained in the neutral comet assay. Among all investigated compounds, MM131 showed the strongest cytotoxic and genotoxic activity toward all tested cell types. In conclusion, our results suggest that MM129, MM130, and MM131 exhibit high cytotoxic and genotoxic potential in vitro, especially towards the colorectal cancer cell line HCT 116. However, further investigations and analyses are required for their future implementation in the field of medicine.     

Monitoring cellular responses upon fatty acid exposure by Fourier transform infrared spectroscopy and Raman spectroscopy

We investigated the applicability of FTIR-spectroscopy as a high throughput screening method for detection of biochemical changes in intact liver cells in bulk upon fatty acid exposure. HepG2 cells adapted to serum free (HepG2-SF) growth were exposed to four different fatty acids, three octadecenoic acids, differing in cis/trans-configuration or double bond position (oleic acid, elaidic acid and vaccenic acid) as well as palmitic acid in three days. High throughput FTIR spectroscopic measurements on dried films of intact cells showed spectra with high signal-to-noise ratio and great reproducibility. When applying principal component analysis (PCA) a clear discrimination between fatty acid exposures was observed. Higher levels of triacylglycerides were accumulated in cells exposed to elaidic acid than when exposed to the other fatty acids; the least accumulation appeared to be in cells exposed to palmitic acid. An increased absorption at ~966 cm(-1) corresponding to trans-double bond was detected upon elaidic acid exposure but not upon vaccenic acid exposure. Instead, upon vaccenic acid exposure two new absorption bands were observed at 981 and 946 cm(-1) due to the presence of double bond conjugation. Raman spectroscopy on single cells, with and without treatment by vaccenic acid, confirmed the presence of conjugation. By fatty acid composition analysis, the conjugation was further specified to be conjugated linoleic acid (CLA) isomers. Thus, instead of being preserved as a monounsaturated fatty acid, vaccenic acid was converted into CLA in HepG2 cells. The results demonstrate the applicability of high-throughput FTIR spectroscopy as an explorative method in in vitro systems from which biologically relevant hypotheses can be generated and further investigated.     

8-Oxodeoxyguanosine Formation in the DNA of Cultured Cells After Exposure to H2O2 Alone or with UVB or UVA Irradiation

Abstract— The purpose of the study was to determine if aluminum phthalocyanine tetrasulfonate (A1PcS₄) photodynamic therapy (PDT) induced the formation of micronuclei in vitro and whether micronuclei formation was dependent on fiuence or cell type. NIH-3T3 and EMT-6 monolayer cultures were incubated in AlPcS₄ (0 or 1 μg/mL) for 24 h, received 0.0, 0.5,1.0 or 1.5 J/cm ² of 675 nm light, then reincubated and harvested at either 24, 48 or 72 h. The micronucleus frequency was determined in binucleated cells using the cytochalasin-block method. Cytotoxicity was assessed by using the 3(4,5-dimenthylthiazoyl-2-yl)2,5(diphenyl-tetrazolium bromide) (MTT) method. The effect of treatment on cell cycle progression was determined by calculating a proliferative index.
Aluminum phthalocyanine tetrasulfonate PDT induced a fluence-dependent increase in the frequency of micro-nuclei in NIH-3T3 and EMT-6 cells. The maximal effect of PDT was obtained in both cell lines 24 h after treatment. NIH-3T3 and EMT-6 cells exposed to a low fiuence of 0.5 J/cm² had a significantly lower number of micro-nuclei per cell 48 h following PDT treatment compared to the number of micronuclei per cell observed 24 h following treatment; however, when cells were exposed to a fluence (1.0 or 1.5 J/cm²) the number of micronuclei per cell did not diminish until 72 h after PDT treatment. The results obtained from the micronucleus assay paralleled those results obtained from the MTT assay.     

Volume exclusion influences in spectral characteristics of DNA-amino acids complexes

Living cells contain a variety of bio molecules including nucleic acids, proteins, polysaccharides, and metabolites as well as other soluble and insoluble components. These bio molecules occupy a significant fraction (20–40%) of the cellular volume. The total concentration of biomolecules reaches 400 g l⁻¹, leading to a crowded intracellular environment referred to as molecular crowding. This causes changes in chemical potential strongly affecting the physicochemical properties in the cell environment. Hence understanding the effects of molecular crowding conditions on biomolecules and biomolecular complexes is of utmost importance. In the present study, interaction of DNA with various amino acids has been observed under the influence of molecular crowding agents of various molecular sizes to understand the changes in DNA characteristics with reference to binding parameters to various amino acids using fluorescence and FTIR spectra. These studies are expected to indicate the changes in the DNA-amino acid complexes with particular significance of effects of molecular crowding in response to volume exclusion effects.     

Photochemical and phototoxic activity of berberine on murine fibroblast NIH-3T3 and Ehrlich ascites carcinoma cells

The present study demonstrates photoinduced generation of superoxide anion radical and singlet oxygen upon UVA irradiation of berberine chloride, and its cytotoxic/phototoxic effects on murine fibroblast non-cancer NIH-3T3 and Ehrlich ascites carcinoma (EAC) cells. The EPR spectra monitored upon photoexcitation of aerated solutions of berberine evidenced the efficient activation of molecular oxygen via Type I and II mechanisms, as the generation of superoxide anion radical and singlet oxygen was observed. The EAC cell line was more sensitive to the effect of non-photoactivated and photoactivated berberine than the NIH-3T3 cell line. UVA irradiation increased the sensitivity of EAC cells to berberine, while the sensitivity of NIH-3T3 cells to photoactivated berberine was not changed. Berberine significantly induced direct DNA strand breaks in tested cells, oxidative lesions were not detected, and the effect of irradiation of cells after berberine treatment did not affect the increase of DNA damage in EAC and NIH-3T3 cells. The DNA damage generated by a combination of berberine with UVA irradiation induced a significant blockage of EAC cells in the S and G(2)/M phases and the stopping/decrease of cell proliferation after 24h of influence. On the other hand, after 36h or 48h of berberine treatment, the DNA damage induced necrotic or apoptotic death of EAC cells. Whether these divergences are caused by differences in the properties of two non-isogenic cell lines or by different berberine uptake and cell localization will be analyzed in our further investigations.     

Study of the Reaction between Nucleic Acids and Tb-BPMPHD-CTMAB Complex and its Analytical Application

The direct use of the fluorescence emission properties of nucleic acids in the investigation of their biological properties is limited, whereas the use of metal complexes as fluorescence probe to study nucleic acids has increased remarkbly. Recently we found that the Tb-l,6-bi(1'-phenyl-3'-methyl-5'-pyrazolone-4'-)hezane-dione(BPMPHD)-trimethyl am-monium bromide(CTMAB) complex can be used as a sensitive fluorescence probe for the determination of nucleic acids.     

Transport, retention and fluorescent measurement of single biological cells studied in microfluidic chips

Cellular manipulation and fluorescent measurement were performed on two types of biological cells. First, transport and retention of yeast cells were demonstrated on a glass microfluidic chip, which consists of special U-shaped microstructures. These microstructures have the openings parallel to the liquid flow and weirs perpendicular to the flow. These allow the retention of yeast cells in the U-shaped pocket and drainage of liquid over the weirs. Thereafter, the same chip was used to carry out real-time fluorescent measurement for the cellular changes in single Jurkat T cells. In this case, the Jurkat cells were localized inside the straight portion of a microchannel. Fluorescent imaging on the same, single suspension cell was carried out to study two cellular processes occurring in viable cells, (1) the intracellular conversion of fluorescein diacetate (FDA) to fluorescein; (2) the degradation of an inhibitory protein, IkappaB, as involved in the NF-kappaB signalling pathway. In the former, the increase in fluorescent intensity of single Jurkat T cells (due to fluorescein formation) was measured; whereas in the latter, the decrease in the fluorescent intensity of a single transfected Jurkat cell (due to the degradation of the IkappaB-EGFP fusion protein) was monitored. In addition, we employed a Jurkat cell expressed with IkappaB-EGFP to probe any possible action of an herbal compound, isoliquiritigenin (IQ), on the degradation of IkappaB-EGFP. These examples have demonstrated that Jurkat cells remain viable within microfluidic channels for cellular studies and that the microfluidic chip can facilitate monitoring of cellular changes of biological cells at the single cell level and in the same cell.     

Virus‐Inspired Polymer for Efficient In Vitro and In Vivo Gene Delivery

Clinical translation of nucleic acids drugs has been stunted by limited delivery options. Herein, we report a synthetic polymer designed to mimic viral mechanisms of delivery called VIPER (virus‐inspired polymer for endosomal release). VIPER is composed of a polycation block for condensation of nucleic acids, and a pH‐sensitive block for acid‐triggered display of a lytic peptide to promote trafficking to the cell cytosol. VIPER shows superior efficiencies compared to commercial agents when delivering genes to multiple immortalized cell lines. Importantly, in murine models, VIPER facilitates effective gene transfer to solid tumors.     

Raman chemical mapping reveals site of action of HIV protease inhibitors in HPV16 E6 expressing cervical carcinoma cells

It has been shown that the HIV protease inhibitors indinavir and lopinavir may have activity against the human papilloma virus (HPV) type 16 inhibiting HPV E6-mediated proteasomal degradation of p53 in cultured cervical carcinoma cells. However, their mode and site of action is unknown. HPV-negative C33A cervical carcinoma cells and the same cells stably transfected with E6 (C33AE6) were exposed to indinavir and lopinavir at concentrations of 1 mM and 30 μM, respectively. The intracellular distribution of metabolites and metabolic changes induced by these treatments were investigated by Raman microspectroscopic imaging combined with the analysis of cell fractionation products by liquid chromatography-mass spectrometry (LC-MS). A uniform cellular distribution of proteins was found in drug-treated cells irrespective of cell type. Indinavir was observed to co-localise with nucleic acid in the nucleus, but only in E6 expressing cells. Principal components analysis (PCA) score maps generated on the full Raman hypercube and the corresponding PCA loadings plots revealed that the majority of metabolic variations influenced by the drug exposure within the cells were associated with changes in nucleic acids. Analysis of cell fractionation products by LC-MS confirmed that the level of indinavir in nuclear extracts was approximately eight-fold greater than in the cytoplasm. These data demonstrate that indinavir undergoes enhanced nuclear accumulation in E6-expressing cells, which suggests that this is the most likely site of action for this compound against HPV.     

Lipophilic nucleic acids — A flexible construction kit for organization and functionalization of surfaces

Lipophilic nucleic acids have become a versatile tool for structuring and functionalization of lipid bilayers and biological membranes as well as cargo vehicles to transport and deliver bioactive compounds, like interference RNA, into cells by taking advantage of reversible hybridization with complementary strands. This contribution reviews the different types of conjugates of lipophilic nucleic acids, and their physicochemical and self-assembly properties. Strategies for choosing a nucleic acid, lipophilic modification, and linker are discussed. Interaction with lipid membranes and its stability, dynamic structure and assembly of lipophilic nucleic acids upon embedding into biological membranes are specific points of the review. A large diversity of conjugates including lipophilic peptide nucleic acid and siRNA provides tailored solutions for specific applications in bio- and nanotechnology as well as in cell biology and medicine, as illustrated through some selected examples.     

Evaluation of Antiproliferative Palladium(II) Complexes of Synthetic Bisdemethoxycurcumin towards In Vitro Cytotoxicity and Molecular Docking on DNA Sequence

Metallodrugs form a large family of therapeutic agents against cancer, among which is cisplatin, a paradigmatic member. Therapeutic resistance and undesired side effects to Pt(II) related drugs, prompts research on different metal–ligand combinations with potentially enhanced biological activity. We present the synthesis and biological tests of novel palladium(II) complexes containing bisdemethoxycurcumin (BDMC) 1 and 2. Complexes were fully characterized and their structures were determined by X-ray diffraction. Their biological activity was assessed for several selected human tumor cell lines: Jurkat (human leukaemic T-cell lymphoma), HCT-116 (human colorectal carcinoma), HeLa (human cervix epitheloid carcinoma), MCF-7 (human breast adenocarcinoma), MDA-MB-231 (human mammary gland adenocarcinoma), A549 (human alveolar adenocarcinoma), Caco-2 (human colorectal carcinoma), and for non-cancerous 3T3 cells (murine fibroblasts). The cytotoxicity of 1 is comparable to that of cisplatin, and superior to that of 2 in all cell lines. It is a correlation between IC₅₀ values of 1 and 2 in the eight studied cell types, promising a potential use as anti-proliferative drugs. Moreover, for Jurkat cell line, complexes 1 and 2, show an enhanced activity. DFT and docking calculations on the NF-κB protein, Human Serum Albumin (HSA), and DNA were performed for 1 and 2 to correlate with their biological activities.     

Nanosecond pulsed electric field induced cytoskeleton, nuclear membrane and telomere damage adversely impact cell survival

We investigated the effects of nanosecond pulsed electric fields (nsPEF) on three human cell lines and demonstrated cell shrinkage, breakdown of the cytoskeleton, nuclear membrane and chromosomal telomere damage. There was a differential response between cell types coinciding with cell survival. Jurkat cells showed cytoskeleton, nuclear membrane and telomere damage that severely impacted cell survival compared to two adherent cell lines. Interestingly, disruption of the actin cytoskeleton in adherent cells prior to nsPEF exposure significantly reduced cell survival. We conclude that nsPEF applications are able to induce damage to the cytoskeleton and nuclear membrane. Telomere sequences, regions that tether and stabilize DNA to the nuclear membrane, are severely compromised as measured by a pan-telomere probe. Internal pore formation following nsPEF applications has been described as a factor in induced cell death. Here we suggest that nsPEF induced physical changes to the cell in addition to pore formation need to be considered as an alternative method of cell death. We suggest nsPEF electrochemical induced depolymerization of actin filaments may account for cytoskeleton and nuclear membrane anomalies leading to sensitization.     

Cell Cycle Kinetics Following UVA Irradiation in Comparison to UVB and UVC Irradiation

Abstract— There is limited information about the carcinogenic effect of longwave ultraviolet radiation (UVA: 315-400 nm). In particular very little is known about the relevant genotoxic damage caused by physiological doses of UVA radiation. A general response of cells to DNA damage is a delay or arrest of the cell cycle. Conversely, such cellular responses after UVA irradiation would indicate significant genotoxic damage. The aim of this study is to compare cell cycle kinetics of human fibroblasts after UVC (190-280 nm radiation), UVB (280-315 nm radiation) and UVA irradiation. Changes in the cell cycle kinetics were assessed by bivariate flow cytometric analysis of DNA synthesis and of DNA content. After UVC, UVB or UVA irradiation of human fibroblasts a suppression was seen of bromodeoxyuridine (BrdU) incorporation at all stages of S phase. The magnitude of this suppression appeared dose dependent. Maximum suppression was reached at 5-7 h after UVB exposure and directly after UVA exposure, and normal levels were reached 25 h after UVB and 7 h after UVA exposure. The lowered BrdU uptake corresponded with a lengthening of the S phase. No dramatic changes in percentages of cells in G₁, S and G₂/M were seen after the various UV irradiations. Apparently, UVA irradiation, like UVB and UVC irradiation, can temporarily inhibit DNA synthesis, which is indicative of genotoxic damage.     

傅里叶变换红外光谱体表无创探测乳腺肿瘤

利用傅里叶变换红外(FTIR)光谱仪联合衰减全反射(ATR)探头的中红外光导纤维对46名健康志愿者及113名乳腺肿物患者的体表皮肤进行无创红外光谱测定, 并从分子水平比较、分析了正常乳腺和有肿物乳腺体表皮肤的红外光谱特征. 结果表明, 健康志愿者乳房皮肤8个FTIR光谱测定部位的图谱趋于一致; 正常乳腺体表与有肿瘤乳腺体表的吸收峰差异明显, 而1080 cm^-1处核酸相关吸收峰的变化对鉴别肿瘤的良、 恶性有重要意义.     

Fluorescent Probes Based on Charge and Proton Transfer for Probing Biomolecular Environment

Fluorescent probes for sensing fundamental properties of biomolecular environment, such as polarity and hydration, help to study assembly of lipids into biomembranes, sensing interactions of biomolecules and imaging physiological state of the cells. Here, we summarize major efforts in the development of probes based on two photophysical mechanisms: (i) an excited-state intramolecular charge transfer (ICT), which is represented by fluorescent solvatochromic dyes that shift their emission band maximum as a function of environment polarity and hydration; (ii) excited-state intramolecular proton transfer (ESIPT), with particular focus on 5-membered cyclic systems, represented by 3-hydroxyflavones, because they exhibit dual emission sensitive to the environment. For both ICT and ESIPT dyes, the design of the probes and their biological applications are summarized. Thus, dyes bearing amphiphilic anchors target lipid membranes and report their lipid organization, while targeting ligands direct them to specific organelles for sensing their local environment. The labels, amino acid and nucleic acid analogues inserted into biomolecules enable monitoring their interactions with membranes, proteins and nucleic acids. While ICT probes are relatively simple and robust environment-sensitive probes, ESIPT probes feature high information content due their dual emission. They constitute a powerful toolbox for addressing multitude of biological questions.     

Probing cell proliferation in the human colon using vibrational spectroscopy: a novel use of FTIR-microspectroscopy

Recently, Fourier transform infrared (FTIR)-spectroscopy has been used to monitor cell growth by several works. Conventionally, the study of cell and tissue dynamics at molecular levels is carried out through various approaches like histochemical methods, application of molecular biology and immunology. Colonic crypts display a pattern in cell growth along their height. Histologically normal sections obtained from formalin fixed biopsies of colon cancer patients were studied in the present work through vibrational spectroscopy. The evolution and development of the normal human colonic crypts manifested in Fourier transform infrared-microspectroscopy (FTIR-MSP) as spectral changes in the levels of nucleic acids, proteins, carbohydrates and lipids. The results indicate that the level of carbohydrates, nucleic acids and lipids increases only till the middle of the crypt up to which the maturation zone is restricted and thereafter decreases till the top where the cells are exfoliated. These observations are in coherence with earlier reports on crypt proliferation. We identify the normal pattern of various biochemicals along the colonic crypt based on data analyzed from FTIR-MSP. This study affords an important example of the application of microscopic vibrational spectroscopy for understanding basic cell processes from formalin fixed tissues where in vivo studies and immunological methods are not feasible.     

Stimuli‐responsive polymers in the 21st century: Elaborated architecture to achieve high sensitivity,fast response,and robust behavior

Life is polymeric in its essence. The living cell contains a range of biopolymers such as proteins, carbohydrates, and nucleic acids. The cells are often compartmentalized via membranes that are composed of lipids. These are small molecules, but they spontaneously aggregate into supermolecular structures. The building blocks of these lipids are among others fatty acids, structures built from methylene oligomers. Biopolymers are sensitive to external stimuli. There are examples where the molecules show a highly non‐linear response to external stimuli. This is seen as moderate changes in structural properties in response to changes in an external parameter until a critical point is reached where a dramatic change in molecular properties takes place upon an incremental change in the external conditions. After the transition, the system responds poorly to further changes. Such non‐linear responses contribute to dramatic cooperative conformational changes leading to strong effects in the biological system. The strong response is an integrated effect of many weak interactions, and it is the cooperativity between all these interactions that are the driving forces for processes occurring in such systems. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

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 (O2*-) and hydroxyl radical (*OH) 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, O2*- and *OH 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% O2*- generation. The drug (5-40 microg 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 *OH radical was further confirmed by using specific quenchers of *OH 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 microg 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 microg 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.