PHOTOREACTIVITY OF PHOTOTOXIC ANTIMALARIAL COMPOUNDS

Abstract— The photochemical reactivity of six phototoxic 2-arylquinolinemethanol antimalarials was examined to understand the chemical mechanism of reaction that causes the in vivo phototoxicity. All of these compounds were found to be photochemically reactive, giving products of photochemical fragmentation involving cleavage of the side chain. The products which are formed, the variation in product distribution with change of solvent and presence of thiols, and photolyses in deuterium-labeled solvents indicate that free radicals are involved in the photofragmentation. There is a good correlation between the quantum efficiency of the photofragmentation reaction and the phototoxicity of the compounds; the more phototoxic compounds react most efficiently, while the less phototoxic compounds react less efficiently. It appears that in vivo free radical reactions caused by the photofragmentation of these compounds are the source of their phototoxicity.     

PHOTOFRAGMENTATION OF PHOTOTOXIC DIBENZOCYCLOHEPTADIENE ANTIDEPRESSANTS

Abstract— Abstract-The products of photochemical reaction of a family of phototoxic tricyclic antidepressants have been determined, both in the presence and absence of oxygen. Under all conditions photofrag-mentation of the phototoxic compounds is an important reaction-in some cases it is virtually the only photoreaction observed. The mechanism of photoreaction appears to involve excited state electron transfer from the side chain to give a reactive exciplex, which fragments via both radical and ionic pathways. These reactive intermediates are likely to contribute to the in vivo phototoxicity of these compounds.     

PHOTOCHEMISTRY OF THE PHOTOTOXIC POLYACETYLENE PHENYLHEPTATRIYNE*

Abstract— Investigation of the photochemistry of the phototoxic polyacetylene phenylheptatriyne, PHT, was undertaken to obtain further information on competing photo-oxidative type II and non-oxidative processes observed in vivo. Laser excitation (308 or 337 nm) led to the formation of a strong triplet signal with a lifetime of 28 μs in MeOH. The triplet was efficiently quenched by the triplet quencher 1,3-octadiene (k_q - 1.6 × 10⁹M^-1s^-1). Quenching by O₂ occurred with a rate constant (1.7 × 10⁹M^-1s^-1) comparable to the rate of electron transfer to methylviologen (1.4 × 10⁹M^-1 s^-1). The formation of singlet oxygen established earlier (type II reaction) in the former case and the semioxidized PHT radical in the latter case are consistent with the competing phototoxic processes observed in vivo.     

高效液相色谱法测定玉米面馒头中着色剂柠檬黄

建立了用高效液相色谱仪测定玉米馒头中柠檬黄的方法.分析柱为Symmetry Shield RP18(3.9 mm ×150mm,5μm),流动相为甲醇-乙酸铵(体积比18:72),流速为0.6 mL/min,检测波长为254 nm,流动相直接提取样品待测组分上机检测.该条件下柠檬黄测定结果的相对标准偏差为2.2%(n=...     

HYDROPHOBICITY-DEPENDENT FLUORESCENCE PROPERTIES AND INTRACELLULAR FLUOROSPECTROSCOPIC BEHAVIOR OF PHOTOTOXIC DRUGS

Fluorospectroscopic behavior of chlorpromazine, mequitazine, afloqualone and piroxicam, which are known to induce skin photosensitivity, was examined in both homogeneous solutions and human buccal mucosal cells. Each drug showed large Stokes' shifts and their fluorescence intensities increased in hydrophobic solvents. These results indicated that the drugs tested can be used as hydrophobic fluorescence probes. Fluorescence microscopic observations of buccal mucosal cells treated with these drugs showed that all the drugs, especially chlorpromazine and mequitazine, were distributed in intracellular membranous regions.     

In vitro EVALUATION OF PHOTOTOXIC PROPERTIES OF FOUR STRUCTURALLY RELATED BENZOPORPHYRIN DERIVATIVES

Four structural analogs of benzoporphyrin derivative (BPD) have been studied and compared for photosensitizing activity in vitro. All analogs have an identical reduced tetrapyrrol porphyrin ring, and differ by the position of a cyclohexadiene ring (fused at either ring A or ring B of the porphyrin) and the presence of either two acid groups or one acid and one ester group at rings C and D of the porphyrin. Photosensitizer activity was tested with the M1 tumor cell line using an assay (the MTT assay) which detects mitochondrial hydrogenases as a measure of cell viability. This assay was shown to be equivalent to the standard clonogenicity or [3H]thymidine uptake assay. Comparative studies with the BPD analogs showed that the monoacid derivatives had equivalent cytotoxicity and were about five-fold more active than the diacid forms. This was the case whether the assays were performed in the presence or absence of fetal calf serum.     

PHOTOSENSITIZED LYSIS OF RED BLOOD CELLS BY PHOTOTOXIC ANTIMALARIAL COMPOUNDS

A family of 12 phototoxic quinolinemethanol antimalarials and three other non-phototoxic clinically used compounds were irradiated in the presence of red blood cells to determine if the resulting hemolysis would be a reliable predictor of phototoxicity. The most phototoxic compounds from in vivo tests were also the most phototoxic in this study. Quinine caused little RBC lysis, paralleling its non-phototoxicity in humans. The quinolinemethanol-induced photohemolysis occurs both in the presence and absence of oxygen. Enriching the RBC with BHA and cholesterol was particularly effective at protecting the cells from photohemolysis. Other compounds offered some measure of protection, while superoxide dismutase and sodium azide, among others, afforded no protection.     

DUAL ROLE OF MELANINS AND MELANIN PRECURSORS AS PHOTOPROTECTIVE AND PHOTOTOXIC AGENTS: INHIBITION OF ULTRAVIOLET RADIATION-INDUCED LIPID PEROXIDATION

Ultraviolet radiation (UVR) is one of the risk factors for skin cancer and the main inducer of melanin pigmentation, the major protective mechanism of mammalian skin against radiation damage. The melanin pigments, eumelanin and pheomelanin, are likely to be important in protection against UVR, but their precursors are generally considered as phototoxic. The available data suggest DNA damage as the mechanism of phototoxicity. However, the effect of melanin precursors on membrane damage through lipid peroxidation, another important and probably more relevant (from the point-of-view of the melanosomal confinement of these molecules) mechanism of phototoxicity, is not known. As a model system for UVR–melanin–membrane interactions, we irradiated liposomes in the presence of eumelanin, pheomelanin and two of their major precursors, 5,6-dihydroxyindole (DHI) and 5-S-cysteinyldopa (SCD). The presence of the two melanin precursors substantially reduced the formation of lipid peroxidation products resulting from UVR exposure. The antioxidant activity of the melanin precursors was diminished under strong prooxidant conditions (presence of Fe³⁺). These results suggest that melanin precursors may have an important role in the protection of skin against the harmful effects of UVR including photocarcinogenesis.     

LIGHT-INDUCED LEAKAGE OF SPIN LABEL MARKER FROM LIPOSOMES IN THE PRESENCE OF PHOTOTOXIC PHENOTHIAZINES

Abstract— Liposomes prepared from dipalmitoyl lecithin, cholesterol and dicetyl phosphate and containing a trapped spin label marker were exposed to long wavelength UV light in the presence of a series of phenothiazine tranquilizers. EPR spectroscopy was used to detect spin label marker released from liposomes, taking advantage of the disappearance of line broadening from electron spin exchange which occurred on spin label release. The minimum effective phototoxic dose in mice of these phenothiazines was also determined. Kinetic studies of light-induced spin label release from phenothiazine-sensitized liposomes showed that membrane damage was rapidly induced and that the damaging species were short-lived. The damage process was oxygen dependent and could be temporarily prevented by cysteamine or α-tocopherol added immediately before irradiation. Only those phenothiazines which mediated light-dependent liposomal membrane damage had phototoxic activity in mice and the degree of photosensitization was parallel in the two systems. In both photosensitization phenomena, the nature of the substituent at the phenothiazine 2-position was more important than the phenothiazine side chain.     

液相色谱法测定果蔬汁中柠檬黄和日落黄方法优化

对液相色谱法测定果蔬汁中柠檬黄和日落黄进行了方法优化,对色谱条件进行了调整,采用ODS-C18型(250 mm×4.6 mm)色谱柱,流动相甲醇-0.02 mol/L乙酸铵(体积比40∶60,pH4),流速为0.6 mL/min。采用紫外检测器,柠檬黄检测波长为430 nm,日落黄检测波长为510 nm。该方法测定结果的相对标准偏差为柠檬黄1.3%(n=4)、日落黄2.3%(n=4)。柠檬黄和日落黄的平均回收率分别为84.17%、88.33%。该法满足实验要求。     

EFFECTS OF 8-METHOXYPSORALEN-INDUCED PHOTOTOXIC EFFECTS ON MAMMALIAN EPIDERMAL MACROMOLECULE SYNTHESIS IN VIVO

Abstract— The influence of 8-methoxypsoralen (8-MOP) and ultraviolet (UVA; 315–400 nm) radiation-induced phototoxic responses on DNA, RNA and protein synthesis and the DNA repair phenomenon were investigated utilizing the hairless mouse epidermis in vivo . The radioactive tracers TdR-³H, cytidine-³H and histidine-³H were used to examine changes in these macromolecules. Using these techniques, we found that the 8-MOP-UVA phototoxic injury inhibited premitotic semiconservative DNA synthesis in the germanitive layer of the epidermis within the first few hours post-irradiation. Recovery occurred by 24 h, followed by a progressive acceleration of this function over the next 7 days. No depression in RNA or protein formation was noted through 36 h. By 48 h the cells in the upper 1/2 to 1/3 of the epidermis lost their normal appearance and discontinued synthesizing these macromolecules. At 72 h RNA and protein synthesis was again active throughout the epidermis and the apparently dead cells had desquamated. At this time the epidermis was notably acanthotic and the epidermal cells were markedly enlarged. Examination for the dark repair response revealed no evidence of unscheduled DNA synthesis following irradiation indicating that the excision repair process was not demonstrable within the first 15min after the phototoxic injury. These responses differ in a number of parameters from the phototoxic reactions induced by UV rays shorter than 320 nm.     

PRIMARY MECHANISMS OF ERYTHROCYTE PHOTOLYSIS INDUCED BY BIOLOGICAL SENSITIZERS AND PHOTOTOXIC DRUGS

Abstract— The elucidation of the molecular mechanism of photosensitized hemolysis of red blood cells may give important clues to the primary events underlying the phototoxic reactions observed in pathological conditions such as porphyria and induced by photosensitizing drugs. Sensitizers effective in photo-hemolysis are porphyrins, the tryptophan metabolite kynurenic acid, and phototoxic drugs such as chlor-promazine and demethylchlortetracycline. Utilizing the singlet oxygen quenchers. jS-carotene and histi-dine and the large deuterium effect on the lifetime of singlet oxygen previously described by us, good evidence of the participation of this excited molecular species in the photohemolysis in the presence of kynurenic acid was obtained. Chlorpromazine and demethylchlortetracycline clearly act by a non-singlet oxygen pathway. The situation observed with haematoporphyrin is less clear and may represent a mixed Type I-Type II mechanism.     

THE EFFECT OF PROTOPORPHYRIN ON HISTAMINE SECRETION BY RAT PERITONEAL MAST CELLS: A DUAL PHOTOTOXIC REACTION

Abstract— Protoporphyrin-induced phototoxicity in rat peritoneal mast cells was manifested either by inhibition of 48/80-stimulated histamine secretion or by cell lysis. At a protoporphyrin concentration of 100ng/m/ (0.17 μM), histamine secretion was completely inhibited after 30min illumination. After initiation, the inhibited state progressed in the dark, and was irreversible, however, it did not develop into cell lysis. More severe phototoxic reactions in mast cells could not be produced by increasing the PP concentration or the incubation time; however, cell lysis was evoked by increasing the light intensity between 180–950W/m², using a light source with emission maxima in the 350–470nm region. Dual phototoxic effects could also be demonstrated in erythrocytes by manipulating the illumination conditions. Increased resistance to osmotic lysis was seen under moderate conditions, and decreased resistance and cell lysis were seen under severe conditions. In the absence of protoporphyrin, the effect of light alone on mast cells was similar to protoporphyrin-phototoxicity, although the light intensities required were higher both for inhibition (60–130W/m²) and lysis (280–950W/m²). The data therefore indicate that certain cell functions can be specifically disrupted by phototoxic reactions that are not cytotoxic; however, phototoxic reactions that lead to severe membrane protein denaturation and cell lysis also occur. The manifestation of these dual effects depends on the intensity of illumination in the 350–470nm region.     

PHOTOTOXIC EFFECTS OF NATURALLY OCCURRING POLYACETYLENES AND α-TERTHIENYL ON HUMAN ERYTHROCYTES

Hemolysis, K⁺ leakage and acetylcholinesterase (AChE) inhibition in human erythrocytes were observed with certain naturally occurring polyacetylenes and a thiophene derivative, α-terthienyl. K' leakage, subsequent hemolysis and AChE inactivation by phenylheptatriyne (PHT), a phototoxic compound, were considerably enhanced by UV light (312–400 nm). The same was true with α-terthienyl and with certain other polyacetylenes. Oxygen enhanced AChE inactivation and hemolysis with α-terthienyl in light. With PHT, only AChE inhibition was significantly enhanced in oxygen. Falcarindiol, a non-phototoxic polyacetylene, did not inactivate this enzyme but caused hemolysis in the dark. Inhibition of AChE and hemolysis by these compounds appear to be unrelated phenomena. These results indicate that certain polyacetylenes are capable of damaging biological membranes in light, and others in dark.     

PHOTOTOXIC EFFECTS OF FOUR PSORALENS ON L1210 CELLS. THE CORRELATION WITH DNA INTERSTRAND CROSS-LINKING

L1210 mouse leukaemia cells were treated with psoralen [S-methoxy-(XMOP), 4,5′,8-trimethyI-(TMP), 4′-hydroxymethyl-4,5′,8-trimethyl-(HMT) or 4′-amino- methyl-4,5′,8-trimethylpsoralen (AMT)] in combination with long wavelength ultraviolct irradiation (Λ～ 365 nm). In order to investigate the relative photobiological activities of the psoralens, cell viability and DNA-synthesis activity as well as psoralen-DNA photoaddition and DNA interstrand cross-linking were measured after the treatment. In all assays the activity ranking order was found to he: TMP > HMT > AM7 > 8MOP. Furthermore, a direct correlation between phototoxicity, psoralen induced DNA interstrand cross-links and inhibition of DNA synthesis was indicated. Finally, psoralen uptake by the cells appears to be an important determinant for phototoxicity, whereas their DNA photoreactivity does not.     

TARGETING OF PHOTOTOXIC DRUGS TO ANTIGEN-SPECIFIC T LYMPHOCYTES in vitro USING ANTIGEN-PRESENTING CELL MEMBRANES

We have used the complex of antigen with class II major histocompatibility proteins (la) in membrane-bound form to target a phototoxic compound to antigen-specific T cell hybridomas in vitro. The iodoacetamidyl ester of phototoxic pyrene was bound covalently to antigen-presenting cells (APC), and protein antigens were added to the cells for processing, presentation and targeting of the drug to three different T hybridomas specific for myelin basic protein (MBP), ovalbumin (OVA) and keyhole limpet hemocyanin (KLH). The B hybridoma LS102.9 was used as APC to present MBP, KLH and either a tryptic digest of OVA or the synthetic peptide OVA323–339to these T cells. A transformed B lymphoma, which expresses trinitrophenol (TNP)-specific surface IgM, A20-HL, was used to present TNP conjugates of KLH and OVA to T cells. Either the antigen-bearing intact APC or Ia⁺ membranes shed spontaneously from them were used as drug carriers to target pyrene to the T cells. In the dark, or in the absence of pyrene, both the intact APC or the shed membranes stimulated interleukin-2 (IL-2) production by the T cells in an antigen-specific way. After UVA (320–400nm) irradiation, both forms of these drug carriers had an antigen-specific toxic effect on the T hybridoma cells with receptors for the antigen that they carried. Both spontaneous T cell proliferation and antigen-induced IL-2 production were inhibited. The shed membranes had a more antigen-specific toxic effect than the intact APC, which tend to settle out with the T cells in the microtiter plates, possibly causing nonspecific contact. These results indicate that the antigen-la complex in membrane-bound form can be used to antigen-target cytotoxic drugs to antigen-specific T cells. The Ia⁺ membranes shed from APC may be useful to target drugs to antigen-specific clones of T cells in vivo.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—IV. THE PHOTOLYSIS OF BENOXAPROFEN, AN ANTI-INFLAMMATORY DRUG WITH PHOTOTOXIC PROPERTIES

Abstract— Benoxaprofen [2-(4-chlorophenyl)-α-methyl-5-benzoxazole acetic acid] is an anti-inflammatory drug that causes acute phototoxicity in many patients. Photolysis studies in organic solvents (ethanol, benzene, dimethylsulfoxide) showed that benoxaprofen underwent both Type I and Type II reactions. Irradiation of an anerobic solution of benoxaprofen in ethanol resulted in hydrogen abstraction from the solvent to yield hydroxyethyl and ethoxyl radicals. In the presence of oxygen, superoxide, singlet oxygen and hydroxyethyl radicals were detected. Photolysis of benoxaprofen in air-saturated benzene or dimethylsulfoxide gave superoxide. However, under anerobic conditions the drug yielded a carbon-centered radical in benzene that could not be identified. These findings suggest that both oxygen-dependent and oxygen-independent processes may be important in the phototoxic reactions of benoxaprofen.     

钻穿与屏蔽效应的从头计算研究

Slater等根据原子结构的量子理论提出用屏蔽常数σ_i表示某自旋轨道i上的电子(简称i电子)所受其它各电子的排斥作用相当于抵消掉若干个核电荷的吸引作用,并通过对各元素的X-射线和光学光谱项的理论分析确定了j-电子对i-电子的屏蔽常数σ_(ji)的一些规律。徐光宪等曾对其加以改进。应用这些规律可判断多电子原子价轨道能级次序,并成功地从理论上阐明由实验确定的电子分层排布规律,使元素周期律从理论上得到发展。“屏蔽”效应主要是表达电子相互排斥的效应。把传统的“钻穿”效应的概念略加改进后,可使其主要表达核对电子吸引作用的效应。为此,定义i-电子轨道半径参量r_(p,i)的概念,     

THE PHOTOTOXIC EFFECT OF BENOXAPROFEN AND ITS ANALOGS ON HUMAN ERYTHROCYTES AND RAT PERITONEAL MAST CELLS

Abstract— Benoxaprofen [2-(4-chlorophenyl)-α-methyl-5-benzoxazoleacetic acid] is a phototoxic non-steroidal anti-inflammatory agent. Irradiation of human erythrocytes in the presence of benoxaprofen (8 μ M ) and oxygen resulted in rapid cell lysis which began after 10 min and was complete within 30 min. While photohemolysis was also observed under anerobic conditions, its onset was delayed for more than 20 min and it took nearly 100 min for complete lysis to occur. Photohemolysis was also delayed by butylated hydroxyanisole but was unaffected by reduced glutathione. 1,4-diazabicyclo[2.2.2]octane, D₂O. β-carotene, or superoxide dismutase. The main photoproduct of benoxaprofen, 2-(4-chlorophenyl)-5-ethylbenzoxazole, was almost as effective in causing photohemolysis as benoxaprofen itself. In the presence of UV irradiation, benoxaprofen (10 (μ M ) caused the degranulation of rat peritoneal mast cells and the release of histamine. The release of mast cell histamine may provide a reasonable explanation for the urticarial response to benoxaprofen and irradiation seen in human subjects.