Temperature-dependent photochemistry of 1,3-diphenylpropenes. The di-pi-methane reaction revisited

The temperature-dependent photochemical behavior of 1,3-diphenylpropene and several of its 3-substituted derivatives has been investigated over a wide temperature range. The singlet state is found to decay via two unactivated processes, fluorescence and intersystem crossing, and two activated processes, trans,cis isomerization and phenyl-vinyl bridging. The latter activated process yields a diradical intermediate which partitions between ground-state reactant and formation of the di-pi-methane rearrangement product. Kinetic modeling of temperature-dependent singlet decay times and quantum yields of fluorescence, isomerization, di-pi-methane rearrangement, and nonradiative decay provides rate constants and activation parameters for each of the primary and secondary processes. Substituents at the 3-position are found to have little effect on the electronic spectra or unactivated fluorescence and intersystem crossing pathways. However, they do effect the activated primary and secondary processes. Thus, the product ratios are highly temperature dependent.

Novel photohydration of non-conjugated aryl/olefin bichromophores within cyclodextrin cavities

Cyclodextrin media are used to achieve photochemical water addition to isolated, acyclic double bonds via intramolecular interaction with excited arenes.

Antibodies directed to drug epitopes to investigate the structure of drug-protein photoadducts. Recognition of a common photobound substructure in tiaprofenic acid/ketoprofen cross-photoreactivity

Drug-induced photoallergy is an immune adverse reaction to the combined effect of drugs and light. From the mechanistic point of view, it first involves covalent binding of drug to protein resulting in the formation of a photoantigen. Hence, determination of the structures of drug-protein photoadducts is of great relevance to understand the molecular basis of photoallergy and cross-immunoreactivity among drugs. Looking for new strategies to investigate the covalent photobinding of drugs to proteins, we generated highly specific antibodies to drug chemical substructures. The availability of such antibodies has allowed us to discriminate between the different modes by which tiaprofenic acid (TPA), suprofen (SUP), and ketoprofen (KTP) photobind to proteins. The finding that the vast majority of the TPA photoadduct can be accounted for by means of antibody anti-benzoyl strongly supports the view that the drug binds preferentially via the thiophene ring, leaving the benzene ring more accessible. By contrast, selective recognition of SUP-protein photoadducts by antibody anti-thenoyl evidences a preferential coupling via the benzene ring leaving the thiophene moiety more distant from the protein matrix. In the case of KTP, photoadducts are exclusively recognized by antibody anti-benzoyl, indicating that the benzene ring is again more accessible. As a result of this research, we have been able to identify a common substructure that is present in TPA-albumin and KTP-albumin photoadducts. This is remarkable since, at a first sight, the greatest structural similarities can be found between TPA and SUP as they share the same benzoylthiophene chromophore. These findings can explain the previously reported observations of cross-reactivity to KTP (or TPA) in patients photosensitized to TPA (or KTP).

Photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids with photosensitizing side effects

The photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids benoxaprofen, carprofen, naproxen, ketoprofen, tiaprofenic acid, and suprofen is reviewed with special emphasis on fundamental photophysical and photochemical properties. The absorption and emission properties of the excited states of these drugs as well as their main photodegradation routes are summarized. The photochemical mechanisms are discussed on the basis of product studies and detection of short-lived intermediates by means of laser flash photolysis. After dealing with the unimolecular processes, attention is focused on the photosensitized reactions of key biomolecules, such as lipids, proteins or nucleic acids. Finally, a short section on the photobiological effects on simple biological models is also included. Although some earlier citations are included, the literature coverage is in general limited to the last decade.

One- vs two-photon processes in the photochemistry of 1,n-dihaloalkanes

1,n-Dihaloalkanes can be photochemical precursors of n-haloalkyl and -allyl radicals and cations, which are generated via one-photon processes. Time-resolved techniques have provided considerable information on the structures and reactivity of these intermediates. Low-temperature matrix isolation, two-laser two-color, laser-drop, and laser-jet photolysis techniques are powerful tools to photolyze haloalkyl radicals and to generate carbenes or biradicals via two-photon processes.

Mechanisms of drug photobinding to proteins: photobinding of suprofen to human serum albumin

Photobinding of drugs to biomolecules constitutes an important early event in the onset of photoallergy. In the present work, UV irradiation of human serum albumin in the presence of either suprofen (SUP) or its major photoproduct, decarboxylated suprofen (DSUP), has been studied as a model system for drug-photosensitised protein binding. Both dark binding and binding in the presence of light were investigated since this will affect the mode, site and mechanism of drug interaction with the protein. In order to determine the binding features of SUP to albumin, competitive binding experiments were carried out using fluorescent probes specific for site I and II. Suprofen was found to selectively dark bind to site II on HSA. Photobinding of DSUP to HSA was more efficient than SUP. Parallel to this, the intrinsic tryptophan fluorescence of HSA decreased when the protein was previously irradiated in the presence of the photoactive compounds, again being DSUP more efficient compared with SUP. As fluorescence quenching involves electron transfer from the excited Trp to the ground state DSUP, it follows that the photoactive compound binding to HSA must be on (or in close proximity to) site I Trp(214) residue. It appears that photobinding of SUP is largely preceded by its photodecomposition to DSUP which, in turn, associates and photobinds to HSA.

Steady-state and time-resolved studies on oxetane cycloreversion using (thia)pyrylium salts as electron-transfer photosensitizers

[reaction: see text] Cycloreversion of oxetane 1 is achieved using (thia)pyrylium salts as photosensitizers. RadicaI cation intermediates involved in the electron-transfer process have been detected using laser flash photolysis. The experimental results are consistent with the reaction taking place from the triplet excited state of the sensitizer.

Photochemistry of 2-hydroxy-4-trifluoromethylbenzoic acid, major metabolite of the photosensitizing platelet antiaggregant drug triflusal

Triflusal is a platelet antiaggregant drug with photoallergic side effects. However, it is considered a prodrug since it is metabolized to 2-hydroxy-4-trifluoromethylbenzoic acid (HTB)--the pharmacologically active form. HTB was found to be photolabile under various conditions. Its major photodegradation pathway appears to be the nucleophilic attack at the trifluoromethyl moiety. The involvement of the triplet state in the photodegradation has been unequivocally proved by direct detection of this transient in laser flash photolysis and by quenching experiments with oxygen, cyclohexadiene and naphthalene. Finally, the photobinding of HTB to proteins such as bovine serum albumin has been demonstrated using ultraviolet-visible (UV-Vis) and fluorescence spectroscopy. Nucleophilic groups present in the protein appear to be responsible for the formation of covalent drug photoadducts, which is the first step involved in the photoallergy shown by triflusal.

The 4,4'-(1,2-ethanediyl)bisbenzyl biradical: its generation, detection, and (photo)chemical behavior in solution

The 4,4'-(1,2-ethanediyl)bisbenzyl biradical (2) is clearly and efficiently generated by photolysis of [3.2]paracyclophane-2-one (8) in cyclohexane solution. This intermediate is also formed via two-photon processes from [2.2]paracyclophane (3) and 1,2-bis(4-chloromethylphenyl)ethane (4). The products arising thermally from biradical 2 are [2.2]paracyclophane and [2.2.2.2]paracyclophane (11) (under high-intensity conditions). Furthermore, two-laser two-color flash photolysis shows that biradical 2 is photostable in solution at room temperature. Thus, formation of p-xylylene (1) from 2 occurs neither thermally nor photochemically.

Mechanism of lipid peroxidation photosensitized by tiaprofenic acid: product studies using linoleic acid and 1,4-cyclohexadienes as model substrates

A careful study of the linoleic acid hydroperoxide (LOOH) profile obtained upon peroxidation of linoleic acid (LA) photosensitized by tiaprofenic acid (TPA) and analogous ketones has been undertaken to distinguish between type-I and type-II photoperoxidation mechanisms. 1,4-Cyclohexadiene and 1,2-dimethylcyclohexa-2,5-dienecarboxylic acid (CHDCA) have also been used as models for LA since they also have double allylic systems. Coirradiation of LA with TPA and decarboxytiaprofenic acid (DTPA) in acetonitrile and micellar media produced significant amounts of conjugated dienic LOOH. The cis,trans to trans,trans ratio depended on the irradiation time; thus, this parameter is an ambiguous tool for mechanistic assignment. An interesting finding was the decrease of the LOOH level after long irradiation times in mixtures photooxidized by DTPA, which is attributed to quenching of the DTPA triplet by the generated dienic LOOH. High-performance liquid chromatography analyses confirmed that the main pathway operating in photodynamic lipid peroxidation sensitized by (D)TPA is a type-I mechanism. However, product studies using CHDCA have clearly shown that a type-II mechanism is also operating and might contribute to the overall photooxidation process in a significant way.

A laser flash photolysis and pulse radiolysis study of primary photochemical processes of flumequine

The 355 nm laser flash photolysis of argon-saturated pH 8 phosphate buffer solutions of the fluoroquinolone antibiotic flumequine produces a transient triplet state with a maximum absorbance at 575 nm where the molar absorptivity is 14,000 M(-1) cm(-1). The quantum yield of triplet formation is 0.9. The transient triplet state is quenched by various Type-1 photodynamic substrates such as tryptophan (TrpH), tyrosine, N-acetylcysteine and 2-deoxyguanosine leading to the formation of the semireduced flumequine species. This semireduced form has been readily identified by pulse radiolysis of argon-saturated pH 8 buffered aqueous solutions by reaction of the hydrated electrons and the CO2*- radicals with flumequine. The absorption maximum of the transient semireduced species is found at 570 nm with a molar absorptivity of 2,500 M(-1) cm(-1). In argon-saturated buffered solutions, the semireduced flumequine species formed by the reaction of the flumequine triplet with TrpH stoichiometrically reduces ferricytochrome C (Cyt Fe3+) under steady state irradiation with ultraviolet-A light. In the presence of oxygen, O2*- is formed but the photoreduction of Cyt Fe3+ by O2*- competes with an oxidizing pathway which involves photo-oxidation products of TrpH.

Development of an expert system rulebase for the prospective identification of photoallergens

Relationships between the structure and properties of chemicals can be programmed into knowledge-based systems such as DEREK (an acronym for 'Deductive Estimation of Risk from Existing Knowledge'). The DEREK knowledge-based computer system contains a sub-set of over 50 rules describing chemical substructures (toxophores) responsible for skin sensitization. This rulebase, based originally on Unilever historical in-house guinea pig maximisation test data, is largely complete and is undergoing refinement as the next stage of its development. As part of an ongoing program of validation and testing, the predictive ability of the sensitization rule set was assessed by processing the structures of over 100 chemical substances in the list of contact allergens identified by the BgVV (German Federal Institute for Health Protection of Consumers). The exercise highlighted areas of chemistry where further development of the rulebase was required, either by extension of the scope of existing rules or by generation of new rules where a sound mechanistic rationale for the biological activity could be established. Several chemicals likely to be acting as photoallergens were identified and rules for photoallergenicity were written covering three classes of chemicals. This paper describes work to extend the DEREK rules for photoallergenicity as part of the European Phototox Project.

Involvement of type I and type II mechanisms in the linoleic acid peroxidation photosensitized by tiaprofenic acid

Analysis of the photomixtures resulting from irradiation of aqueous solutions of linoleic acid sensitized by tiaprofenic acid (TPA) or its major photoproduct (DTPA) by HPLC has shown the formation of all the four possible conjugated dienic hydroperoxides. According to laser flash photolysis experiments the rate constants for hydrogen abstraction from linoleic acid by the excited triplet states of TPA and DTPA are 2 x 10(5) and 3.2x 10(5) M(-1) s(-1), respectively. These data, together with the known rate constants for oxygen quenching of triplet (D)TPA and for the reaction of singlet oxygen with linoleic acid, show that the mechanism is mixed type I/type II. Finally, typical radical scavengers such as BHA and singlet oxygen quenchers such as DABCO and sodium azide are efficient quenchers of the triplet excited state of DTPA. This shows the risk of assigning mechanisms based on indirect 'evidences' using 'specific' additives.

Photobinding of carprofen to protein

Carprofen is a non-steroidal antiinflammatory drug with marked photosensitising properties. In order to elucidate the mechanisms underlying the phenomenon of drug-protein photobinding, mixtures of the drug and human serum albumin were irradiated under different experimental conditions. After irradiation and subsequent gel-filtration chromatography of the photomixture, the eluting protein fraction was analysed by means of fluorescence spectroscopy. The formation of drug-protein photoadducts could be evidenced by the characteristic emission properties of the carbazole chromophore. The photobinding of the drug to human serum albumin appears to involve the formation of aryl radicals resulting from carbon-halogen photocleavage. This mechanistic interpretation is supported by the observed variations in the intensity of the fluorescence spectra, which can be correlated with the lower quantum yield emission of chlorocarbazoles as compared to non-halogenated analogues. The results from laser flash photolysis studies are also in agreement with this proposal.

Synthesis and biological evaluation of new analogues of the active fungal metabolites N-(2-methyl-3-oxodecanoyl)-2-pyrroline and N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline (II)

New analogues of the bioactive enamides isolated from P. brevicompactum (2 and 3) have been synthesized to improve the biological activities. Two different structural modifications have been introduced: substitution of the aliphatic side chain present in the natural products (1-4) by other groups frequently found in other active compounds and use of other nitrogen-containing five-membered rings with different degrees of oxidation. In this way, the insecticidal and fungicidal activities have been improved. Thus, compound 9, which possess a 3-pyrroline ring, exhibited important insecticidal activity against third-instar nymphs of Oncopeltus fasciatus Dallas (100% mortality at 7.5 microg/cm(2)). Remarkable fungicidal activity was also found, and preliminary structure-activity relationships could be established.

Tiaprofenic acid-photosensitized damage to nucleic acids: a mechanistic study using complementary in vitro approaches

In order to determine whether or not tiaprofenic acid (TPA) could cause cellular DNA damage, human fibroblasts were irradiated in the presence of the drug and subsequently examined by means of the comet assay. This led to the observation that TPA actually sensitizes cellular DNA to the subsequent irradiation. When TPA was irradiated in the presence of supercoiled plasmid DNA, it produced large amounts of single-strand breaks (SSB); this is consistent with the effects observed on cellular genomic DNA by the comet assay. More importantly, low concentrations of TPA, unable to produce direct SSB, caused photo-oxidative damage to DNA as revealed by the use of excision-repair enzymes. The fact that TPA-irradiated DNA was a substrate of formamidopyrimidine glycosylase as well as endonuclease III revealed that both purine and pyrimidine bases were oxidized. This was further supported by the TPA-photosensitized oxidation of 2'-deoxyguanosine which led to a product mixture characteristic of mixed type-I/II mechanisms. Thymidine was less reactive under similar conditions, but it also decomposed to give a typical type-I product pattern. Accordingly, the TPA triplet was quenched by the two nucleosides with clearly different rate constants (10(8) vs 10(7) M-1 s-1, respectively). As cellular RNA also contains oxidizable bases, it could be the target of similar processes, thus interfering with the biosynthesis of proteins by the cells. Extraction of total RNA from TPA-irradiated human fibroblasts, followed by gel electrophoresis and PCR analysis, confirmed this hypothesis. Finally, photosensitization experiments with Saccharomyces cerevisiae showed that, in spite of an efficient drug-yeast interaction leading to cytotoxicity, neither intergenic recombination nor gene conversion took place. Thus, while TPA-photosensitized damage to nucleic acids can result in genotoxicity, the risk of mutagenicity does not appear to be significant.

A photophysical and photochemical study of 6-methoxy-2-naphthylacetic acid, the major metabolite of the phototoxic nonsteroidal antiinflammatory drug nabumetone

Nabumetone is a phototoxic nonsteroidal antiinflammatory drug used for the treatment of osteoarthritis. However, nabumetone is considered a prodrug with its metabolite 6-methoxy-2-naphthylacetic acid the active form. Photophysical and photochemical studies on this metabolite have been undertaken. It undergoes photodecarboxylation in aerated aqueous and organic solvents. In addition to the accepted photodegradation pathway for related molecules, a new mechanism that implies generation of the naphthalene radical cation from the excited singlet and addition of O2 prior to the decarboxylation process has been demonstrated. Evidence for the involvement of the excited singlet state in this mechanism have been obtained by steady-state and time-resolved fluorescence experiments. The fluorescence quenching by O2 and the shorter singlet lifetime in aerated solvents support this assignment. Laser flash photolysis also supports this mechanism by showing the noninvolvement of the triplet in the formation of the naphthalene radical cation. Finally, the well-known electron acceptor CCl4 acts as an efficient singlet quencher, enhancing the route leading to the radical cation, preventing intersystem crossing to the triplet and thus resulting in a dramatic increase in the yield of 6-methoxy-2-naphthaldehyde, the major oxidative decarboxylation product; this constitutes unambiguous proof in favor of the new mechanistic proposals.

Evaluation of IgG, IgM, and IgA antibodies to mycoplasma penetrans detected by ELISA and immunoblot in HIV-1-infected and STD patients, in São Paulo, Prazil

The aim of the present study was to determine the frequency of IgG, IgA, and IgM antibodies to Mycoplasma penetrans in HIV-1-infected patients and in patients with sexually transmitted diseases. We tested serum samples from 106 HIV-1-positive patients and 110 individuals with clinical symptoms of urethritis. ELISA and the immunoblot test were performed using M. penetrans lipid associated membrane proteins as antigen. By ELISA, we found a higher frequency (P < 0.05) of IgG against M. penetrans in HIV-1-infected and STD patients (25.5 and 17.3%) than in controls (1.2%), as well as a higher frequency of IgA (P < 0.05) (15.1 and 17.3% compared to 1.2%). For IgM, no differences were observed (P >/= 0.05) (3.8, 9.1, and 5. 8%, respectively). When the frequencies of IgG, IgM, and IgA antibodies of the HIV-1-infected patients were compared taking into account the CD4/CD8 cell ratios < 0.3 and >/= 0.3, no significant differences were observed between the two groups (13.3, 10, and 20%, compared to 20, 0, and 5%, respectively) (P > 0.05), possibly due to the low number of samples on which we could perform T-cell counts (53/106). The M. penetrans peptide of 38 kDa, considered immunodominant, was recognized in immunoblot by 51.8% of positive sera by ELISA for IgG, 50.0% for IgM, and 75% for IgA in the AIDS patients group, and by 47.4, 60.0, and 75.0%, respectively, in the sexually transmitted disease group. Cross-reactions in immunoblot for IgG were observed in sera from individuals infected with Mycoplasma pneumoniae and Mycoplasma hominis, and cross-reactions in immunoblot for IgA were observed in sera from individuals infected with M. hominis; all of them were ELISA negative to M. penetrans.

Synthesis and biological evaluation of new analogues of the active fungal metabolites N-(2-methyl-3-oxodecanoyl)-2-pyrroline and N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline

To evaluate the effect of simplifying the beta-ketoamide system present in active isolated metabolites from Penicillium brevicompactum (2 and 3) on the activity, new analogues with a monocarbonylic amide functionality have been obtained. In this way, the insecticidal and fungicidal activities have been improved in relation to the natural products taken as lead molecules. Thus, two of the synthetic analogues (5a and 5b) showed very important insecticidal activities against third-instar nymphs of Oncopeltus fasciatus Dallas, with acute LD(50) values of 3.0 and 1.5 microg/cm(2), respectively. Moreover, some analogues showed good levels of fungicidal activity against a wide range of commercially important and taxonomically diverse fungi; remarkably, compound 7c has proved to be highly active against Colletotrichum gloesporoides and Colletotrichum coccodes, with ED(50) values of 2.04 and 11.7 microg/mL, respectively.

Lysosomes are sites of fluoroquinolone photosensitization in human skin fibroblasts: a microspectrofluorometric approach

The fluoroquinolone antibiotics are widely used despite their strong phototoxicity under solar UV irradiation. Although they are known as good photodynamic photosensitizers, other factors than production of activated oxygen species may play a role in the effectiveness of the phototoxic effect. Subcellular localization is one of the important parameters that may determine this strength. Using microspectrofluorometry, it is shown that norfloxacin, ofloxacin, lomefloxacin, ciproflaxin and BAYy3118 are readily incorporated into lysosomes of HS68 human skin fibroblasts although weak staining of the whole cytoplasm also occurs especially with norfloxacin. Consistent with their photoinstability in solutions, the fluoroquinolones under study are readily photobleached by UVA in the HS68 fibroblasts. The BAYy3118 derivative that has the fastest bleaching rate also shows the strongest phototoxicity toward HS68 fibroblasts. Photosensitization with these fluoroquinolones induces lysosomal membrane damage as shown by the increased rate of leakage of the lysosomal probe lucifer yellow as compared to that observed with untreated cells.

Vertical shear injuries: is there a relationship between residual displacement and functional outcome?

BACKGROUND

Residual vertical displacement is often cited as being related to poor outcome in patients with pelvic injuries. This study attempts to clarify the relationship between residual vertical displacement and functional outcome.

METHODS

From 1982 to 1989, over 500 patients with pelvic ring injuries were treated at two Level I trauma centers. Thirty-three patients with vertical shear (Tile C) fractures and residual displacement (2-52 mm) were evaluated. Outcomes were quantified by using SF-36 Short-Form Health Survey (SF-36) and the Iowa Pelvic Score (IPS).

RESULTS

There was no correlation between IPS or SF-36 scales and residual vertical displacement. The IPS correlated (p<0.05) with seven of eight SF-36 categories, excluding mental health. Patients reporting limp and leg length discrepancy also correlated with the IPS and select SF-36.

CONCLUSION

Pelvic injuries showed no correlation between functional outcome and residual vertical displacement suggesting other factors. The degree of residual vertical displacement does not affect functional outcome.

Insecticidal, anti-juvenile hormone, and fungicidal activities of organic extracts from different Penicillium species and their isolated active components

Organic extracts from mycelium and culture broth of 21 Penicillium isolates have been tested for insecticidal, insect anti-juvenile hormone (anti-JH), and antifungal activities. Culture broth extracts were the most active, mainly against insects; nearly 25% of them have shown high entomotoxicity (100% mortality at 100 microg/cm(2)). A strong in vivo anti-JH activity against Oncopeltus fasciatus Dallas was detected in the culture broth extracts from P. brevicompactum P79 and P88 isolates. The two new natural products isolated from P79, N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline (1) and 2-hept-5-enyl-3-methyl-4-oxo-6,7,8,8a-tetrahydro-4H-pyrrolo[2,1-b]-1, 3-oxazine (2), possessed anti-JH and insecticidal activity, respectively, against O. fasciatus. Synthesized natural compound 1 has shown an ED(50) of 0.7 microg/nymph when assayed on newly molted fourth-instar nymphs of O. fasciatus. Promising biological activities have also been detected in the synthetic precursors.

Cerebral tumor-like American trypanosomiasis in acquired immunodeficiency syndrome

Cerebral tumor-like American trypanosomiasis (CTLAT) is an uncommon complication of Chagas' disease, observed only in immunosuppressed patients. We assessed 10 human immunodeficiency virus-positive patients with Chagas' disease who presented with CTLAT. All patients had neurological involvement and 6 developed intracranial hypertension. Neuroimaging studies showed supratentorial lesions in 9 patients, being single in 8. One case had infratentorial and supratentorial lesions. Low CD4+ cell counts were observed in all the cases and in 6 of them CTLAT was the first manifestation of acquired immunodeficiency syndrome. Serological tests for Chagas' disease were positive in 6 of 8 patients. Trypanosoma cruzi was identified in all brain specimens and in three cerebrospinal fluid samples. CTLAT should be considered in the differential diagnosis of intracranial mass lesions in human immunodeficiency virus-positive patients and should be added to the list of acquired immunodeficiency syndrome-defining illnesses.

Photobinding of tiaprofenic acid and suprofen to proteins and cells: a combined study using radiolabeling, antibodies and laser flash photolysis of model bichromophores

Drug photoallergy is a matter of current concern. It involves the formation of drug-protein photoadducts (photoantigens) that may ultimately trigger an immunological response. Tyrosine residues appear to be key binding sites in proteins. The present work has investigated the photobinding of tiaprofenic and (TPA) and the closely related isomer suprofen (SUP) to proteins and cells by means of radioactive labelling and drug-directed antibodies. To ascertain whether preassociation with the protein may play a role in photoreactivity, two model bichromophoric compounds (TPA-Tyr and SUP-Tyr) have been prepared and studied by laser flash photolysis. The results of this work show that (a) TPA and SUP photobind to proteins with similar efficiencies, (b) both drugs form photoadducts that share a basic common structure, as they are recognized by the same antibody and (c) drug-protein preassociation must play a key role in photoreactivity, as indicated by the dramatic decrease in the triplet state lifetimes of the model bichromophores compared to the parent drugs.

Release of inflammatory mediators (PGE2, IL-6) by fenofibric acid-photosensitized human keratinocytes and fibroblasts

Ultraviolet-A radiation has weak effects on the release of inflammatory mediators by skin cells due to the poor overlap between UVA wavelengths and the absorption spectra of the relevant chromophores of key biomolecules. However, this situation could be very different in the presence of a photosensitizing drug. To investigate this issue, we have irradiated human skin cells (keratinocytes and fibroblasts) in the presence of fenofibric acid (the active phototoxic metabolite of fenofibrate). The results of this research show a dual effect on the production/release of inflammatory mediators: the synthesis of the proinflammatory cytokine interleukin-6 becomes strongly inhibited at photosensitizer concentrations that clearly stimulate the production of prostaglandins (PGE2) by skin cells. We have found evidences showing that the de novo synthesis of cytokines is inhibited in photosensitized cells due to the fact that cellular mRNA is degraded. Interestingly, when the medium taken from irradiated cultures is added to nonexposed cells, a significant stimulation of cytokine synthesis is observed that can be inhibited by anti-PGE2 antibodies. These observations may be relevant in vivo, where prostaglandins released by photosensitized skin cells could stimulate cytokine synthesis by underlying, nonirradiated cells.

Phototoxicity associated with diclofenac: a photophysical, photochemical, and photobiological study on the drug and its photoproducts

Diclofenac (1) is a photosensitizing nonsteroidal antiinflammatory drug. Its photodecomposition gives rise to chlorocarbazole 2a. This product undergoes photodehalogenation to 3a in a subsequent step. When the photobiological activities of 1, 2a, and 3a are compared by means of the photohemolysis test, it is clearly observed that chlorocarbazole 2a causes cell lysis with a markedly higher efficiency than the parent drug or the secondary photoproduct 3a. Laser flash photolysis studies suggest that photodehalogenation of 2a occurs from its excited triplet state via quenching by ground-state 2a and formation of an excimer. As a consequence, an aryl radical plus an N-centered carbazolyl radical are formed. These radical intermediates appear to be responsible for the observed photobiological effects of diclofenac, via hydrogen abstraction from the target biomolecules, which initiates a type-I photodynamic effect. The efficient peroxidation of model lipids, such as linoleic acid, photosensitized by 2a are in favor of this proposal. Thus, the photosensitizing properties of diclofenac appear to be associated with the photochemical and photobiological activity of its major photoproduct.

Triplet photoreactivity of the diaryl ketone tiaprofenic acid and its decarboxylated photoproduct. Photobiological implications

The 2-benzoylthiophene chromophore of the photosensitizing drug tiaprofenic acid and of its decarboxylated derivative is characterized by a unusually high energy gap between the T1 (pi, pi*) and T2 (n, pi*) excited states, which makes this a unique system to study the intrinsic photoreactivity of the two states. Weak fluorescence and phosporescence emission were detected at room temperature. Tiaprofenic acid undergoes photodecarboxylation from the triplet manifold as the main reaction. The photoprocess is temperature dependent with activation energy of 7-10 kcal/mol, close to the energy gap between T1 and T2. The decarboxylated product abstracts hydrogen in type I reactions. The involvement of T2 in the above processes is proposed. Moreover the decarboxylated derivative exhibits reactivity toward phenols, consistent with a participation of the T1 state as electron acceptor. The observed photoprocesses can account for biological photosensitization reactions, like membrane damage and protein modification.

Photosensitizing drugs containing the benzophenone chromophore

The nonsteroidal anti-inflammatory agents ketoprofen, tiaprofenic acid, suprofen and tolmetin, together with the anti-hyperlipoproteinemic drug fenofibrate and the anti-arrhythmic amiodarone can be included in the group of benzophenone-derived photosensitizing drugs. They contain a diaryl ketone chromophore and mediate the development of phototoxic reactions. In some cases, photoallergic responses have been reported. These properties have been substantiated in clinical reports, as well as by means of in vivo and in vitro assays. Tolmetin is phototoxic in vitro, however there are no reports on photosensitization by this drug in humans. In general, photochemical and photobiological studies strongly suggest that photosensitization involves formal hydrogen abstraction (either in a single step or via electron transfer followed by proton transfer) by the benzophenone-like chromophore from the excited triplet state. In the case of amiodarone, the radicals generated by photodehalogenation from the triplet are responsible for the photosensitivity side-effects.

Drug-photosensitized protein modification: identification of the reactive sites and elucidation of the reaction mechanisms with tiaprofenic acid/albumin as model system

Certain drugs can photosensitive the formation of protein modifications, which are thought to be responsible for the occurrence of photoallergy. In the present work, the UV irradiation of serum albumin in the presence of tiaprofenic acid has been studied as a model system for drug-photosensitized protein modifications. The photolysates evidenced that His, Tyr, and Trp are the reactive sites of the protein. The experimental results strongly suggest that formal hydrogen abstraction from the OH or NH groups of Tyr or Trp by the excited drug is the key photochemical process. Competition between cage escape and in cage recombination of the resulting radical pairs governs the final outcome: protein photo-cross-linking versus drug-protein adduct formation. These findings are highly relevant to understand the process of photohapten formation, the first event in the onset of photoallergy.

Photodegradation and photobinding of tiaprofenic acid: in vitro versus in vivo

The photoreactivity of the photosensitizing nonsteroidal anti-inflammatory drug tiaprofenic acid (TA) and its photoproduct decarboxytiaprofenic acid (DTA) was studied both in the presence and in the absence of bovine serum albumin (BSA). The photoproduct DTA was found to be photostable in buffered aqueous solution at pH 7.4, but photodecomposed when BSA was present in the reaction medium. Both TA and DTA underwent irreversible photobinding to BSA in an almost quantitative way, as evidenced by radioactivity measurements using labeled (3H) compounds. In the case of TA, it has been proven that photobinding is mainly attributable to the phototoreactivity of in situ-generated DTA. The photodegradation and photobinding of TA were also investigated in the epidermis in vivo. Rats were exposed to UVA after application of TA to their shaven dorsal skin. During the initial periods of irradiation, the amount of TA decreased sharply, and the yield of the corresponding photoproduct (DTA) reached a maximum. Prolonged irradiation led to photodegradation of DTA. In vivo photobinding was studied using 3H-TA. Photobinding took place slowly at the beginning, but its rate increased sharply after complete photoconversion of TA, when the photoproduct DTA reached the maximum concentration. Thereafter, the decrease of DTA was more pronounced than that of TA. This indicates that-also in vivo-DTA rather than TA is responsible for the photobinding to biomacromolecules in the viable layer of the epidermis. Overall, the above results suggest that irradiation of TA in buffered aqueous solution, in the presence of proteins, is a reasonable model system to study the photodegradation and photobinding behavior of this drug in vivo. From the qualitative point of view, the main conclusion is that DTA plays a key role both in vivo and in vitro: it is the major photoproduct, it undergoes further photodegradation upon prolonged irradiation, and it appears to be responsible for the photobinding process.

Photophysical and photochemical characterization of a photosensitizing drug: a combined steady state photolysis and laser flash photolysis study on carprofen

Carprofen (1a) is a photosensitizing nonsteroidal anti-inflammatory drug. It undergoes photodehalogenation from its triplet excited state. The resulting aryl radical (II) is able to abstract hydrogen atoms from model lipids, mediating their peroxidation by a type I mechanism. This aryl radical intermediate appears to be responsible for the observed photobiological effects of carprofen. The active involvement of the triplet state has been confirmed by direct detection of this species in laser flash photolysis and by quenching experiments with cyclohexadiene and naphthalene. Carprofen also photosensitizes singlet oxygen production with a quantum yield of 0.32. A minor reaction pathway is photodecarboxylation, which occurs from the excited singlet state and leads to an acetyl derivative (1b). In the case of the dehalogenated photoproduct (2a), photodecarboxylation to the ethyl (2d) and acetyl (2b) derivatives, together with singlet oxygen production (quantum yield = 0.18), is also possible. However, the biological activity of 2a in the linoleic acid photoperoxidation and photohemolysis tests is markedly lower than that of 1a, which constitutes further evidence in favor of the important role of photodehalogenation in the adverse photobiological effects of carprofen.

Management of humeral nonunion after the failure of locking intramedullary nails

We reviewed 21 cases of humeral nonunion following the failure of "locking" humeral nails. The nails had been inserted as the primary operative procedure following humeral fracture in fifteen cases or after the failure of closed treatment in six cases. Reconstruction after the failure of these implants was complicated by poor bone stock and difficulty in achieving union. Although technically difficult, open reduction and internal fixation with plating and bone grafting (successful in nine of nine cases) was more consistent than exchange nailing (successful in four of 10 cases) in achieving union (p = 0.01). Two patients refused further surgical intervention. The degree of bone loss associated with a loose nail, the lack of success of exchange nailing, and the insertion site morbidity associated with humeral nail removal differentiate these nonunions from similar lower extremity problems. The degree of bone loss following failed locking nailing of the humerus is a major concern, and exchange nailing alone may not be an acceptable option to deal with this problem.

Pelvic ring injuries. A long term functional outcome study

Eighty patients with pelvic fractures, without hip, spine injuries with neurologic deficits, or traumatic cognitive deficits, 61% treated with external fixators, were reviewed with greater than 5 years of followup. The Short Form-36 General Health Survey, the Iowa pelvic scores, and additional questionnaires concerning return to previous sexual function, occupation, and recreation, and a perception of the worst sequelae of their pelvic trauma were administered. Fractures were classified according to Tile as 25 undisplaced Class A, 31 rotationally displaced Class B, and 24 vertically displaced Class C fractures. Injury severity scores, associated injuries, and mechanisms of injuries were similar across Tile classes. Statistical analysis compared Tile Classes A with B with C and Classes A with B and C. Variations by Tile class among the Short Form-36 survey, Iowa pelvic score, or questionnaire result's were not seen. Approximately 75% of patients returned to their previous sexual function and 80% to their previous occupation. Similarities comparing undisplaced with displaced pelvic fractures question whether reduction of pelvic ring injuries can alter patient long term functional outcomes.

Gas chromatographic-mass spectrometric study of photodegradation of carbamate pesticides

The photodegradation of seven carbamate pesticides (bendiocarb, isoprocarb, promecarb, ethiofencarb, furathiocarb, fenoxycarb and pirimicarb), in aqueous solution, has been examined by GC-MS. The most general result was formation of the corresponding phenols. Irradiation of isoprocarb and promecarb also resulted in photo-Fries rearrangement to ortho- and para-hydroxybenzamides. In the case of ethiofencarb photocleavage of the carbon-sulfur bond gave 2-methylphenyl methylcarbamate as main product. Likewise, N-S bond cleavage occurred upon irradiation of furathiocarb, to allow the formation of the carbamate insecticide carbofuran, butyl methylcarbamate and carbofuranphenol. Under similar conditions, fenoxycarb gave p-phenylphenol and 2-hydroxydibenzofuran, through primary homolysis of the aryloxy-methylene bond. Finally, pirimicarb gave rise to 2-formylamino-5,6-dimethylpyrimidin-4-yl dimethylcarbamate.

Photodegradation of bezafibrate in aqueous media. Studies of its in vitro phototoxicity

Aqueous solutions of the antihyperlipoproteinemic drug bezafibrate (CAS 41859-67-0) are photolabile towards UV-B light under aerobic conditions. Two compounds were isolated and identified spectroscopically as well as by alternative synthesis as the only photoproducts formed. Their formation involves primary cleavage of the aryloxy-carbon bond and decarboxylation followed by hydrogen abstraction or dimerization. Bezafibrate is phototoxic in vitro as indicated by the photohemolysis test. Furthermore bezafibrate photo-sensitizes peroxidation of linoleic acid as monitored by the UV detection of dienic hydroperoxides. Partial inhibition of these processes on addition of butylated hydroxyanisole (BHA), reduced glutathione (GSH), sodium azide (NaN3) or 1,4-diazabicyclo [2.2.2] octane (DABCO) suggests the involvement of type I as well as type II mechanisms.

Lamp versus Laser Photolysis of a Bichromophoric Dichloroalkane: Chemical Evidence for the Two-Photon Generation of the 1,5-Diphenylpentanediyl Biradical

Low intensity (lamp) photolysis of 1,5-dichloro-1,5-diphenylpentane (1) leads to the formation of the 1-chloro-1,5-diphenylpentyl radical (7) through C-Cl bond cleavage. Radical 7 leads to the final products through typical free radical reactions. No cyclopentanes are formed under low intensity conditions. In contrast, high intensity laser irradiation leads to C-Cl photocleavage of radical 7 to yield the 1,5-diphenylpentanediyl biradical (11), which results in the formation of isomeric cis- and trans-1,2-diphenylcyclopentanes; the behavior of these biradicals agrees well with that observed when their precursor is 2,6-diphenylcyclohexanone. Two-color two-laser experiments suggest that both singlet and triplet biradicals are formed, even if only the latter are detectable with nanosecond techniques.

Nonreamed nailing of closed and minor open tibial fractures in patients with blunt polytrauma

A retrospective comparison of dynamic and static locking mode nonreamed nails in 88 closed, Grades I and II open tibial fractures is presented. Amount of time and number of reoperations required to unite fractures were compared for dynamic (Group 1, n = 31) and static locked (Group 2, n = 13) Winquist I and II fractures, and dynamic (Group 3, n = 14) and static locked (Group 4, n = 30) Winquist III, IV, and segmental fractures. Total reoperations also were compared; Tibias treated with dynamic nails united in an average of 20 weeks, with 3 reoperations; tibias treated with static locked nails united in an average of 30 weeks, with 21 reoperations. Group 1 fractures united in an average of 20 weeks, with 1 reoperation; Group 2 fractures united in an average of 32 weeks, with 4 reoperations. Group 3 fractures united in an average of 20 weeks; Group 4 fractures united in an average of 29 weeks, with 11 reoperations. In the group of tibias treated with dynamic nails, 3 additional operations were done; in the group of tibias treated with static locked nails, 7 additional operations were done. There was 1 infection and 3 deformities. Static locking mode appeared to delay union, especially when Groups 1 and 2 are compared; these fractures can be nailed without locking screws.

Synthesis and pharmacological evaluation of 2'-hydroxychalcones and flavones as inhibitors of inflammatory mediators generation

2'-Hydroxy-3,4-dimethoxy-3',4'-dimethylchalcone (3a), 2'-hydroxy-3',4',3,4-tetramethoxychalcone (3b), and their corresponding flavones, 3',4'-dimethoxy-7,8-dimethylflavone (4a) and 3',4',7,8-tetramethoxyflavone (4b), were prepared from 3,4-dimethoxycinnamic acid and the respective phenol. The four compounds inhibited enzymic lipid peroxidation and showed weak peroxyl scavenging activity. They also reduced LTB4 release from human neutrophils stimulated by A23187. The chalcone 3b was the only compound able to inhibit in a concentration-dependent way, synovial human recombinant phospholipase A2 activity, human platelet TXB2 generation, and human neutrophil degranulation. This chalcone exerted topical antiinflammatory effects in mice.

Molecular basis of drug phototoxicity: photosensitized cell damage by the major photoproduct of tiaprofenic acid

Tiaprofenic acid is a photosensitizing nonsteroidal anti-inflammatory drug, whose major photoproduct (decarboxytiaprofenic acid) is also a potent photosensitizer. Because of the lack of the carboxylate moiety, this photoproduct is more lipophilic and might bind more efficiently to cell membranes, thereby causing phototoxic damage. To verify the feasibility of this hypothesis, we have prepared the 3H-labeled analogs of tiaprofenic acid and its photoproduct and examined the binding, persistence and phototoxicity of the photoproduct using poorly metabolizing (fibroblasts) and actively metabolizing cells (hepatocytes). The photoproduct of tiaprofenic acid accumulates in both cell types as it is formed. Upon removal of the photoproduct from the culture medium, it rapidly disappears from hepatocytes but not from fibroblasts. Consequently, irradiation of fibroblasts previously incubated with the photoproduct and kept in culture in the dark for 20 h results in generalized cell damage while this effect is not observed in hepatocytes. Because of its long persistence in poorly metabolizing skin cells and its reluctance to photobleaching, the formation of this photoproduct in skin may be of relevance to explain the in vivo phototoxicity of tiaprofenic acid.

Femoral plating

We have demonstrated that we are able to meet both trauma and orthopedic goals with immediate plate fixation of femoral fractures in patients with blunt polytrauma. Our femoral fracture mortality rate is less than our predicted institutional mortality rate of patients with comparative injury severity scores. Ipsilateral femoral neck and shaft fractures are easily repaired with femoral plating. Infections, even in open fractures and systemically unstable patients, are rare. Implant failures have been infrequent and are easily reconstructed with intramedullary nails. Knee motion has been restored reliably. Stainless steel DCP plate fixation requires primary bone grafting. Achieving union and subsequent knee rehabilitation often requires that patients remain on crutches for up to 6 months. Our experience with titanium LCDCP plates is preliminary, but we are seeing a significant amount of callus formation and, perhaps, earlier union and bearing weight.

Photochemical and photobiological properties of ketoprofen associated with the benzophenone chromophore

Irradiation of ketoprofen in neutral aqueous medium gave rise to 3-ethylbenzophenone as the major photoproduct. Its formation is justified via protonation of a benzylic carbanion or hydrogen abstraction by a benzylic radical. Minor amounts of eight additional compounds were isolated. Four of them are derived from the benzylic radical: 3-(1-hydroperoxyethyl)benzophenone, 3-(1-hydroxyethyl)benzophenone, 3-acetylbenzophenone and 2,3-bis-(3-benzoylphenyl)butane. The other four products involve initial hydrogen abstraction by the excited benzophenone chromophore of ketoprofen: 1,2-bis-(3-ethylphenyl)-1,2-diphenyl-1,2-ethanediol, 2-(3-benzoylphenyl)-1-(3-ethylphenyl)-1-phenylpropan-1-ol, alpha-(3-ethylphenyl)phenylmethanol, 1,2-bis-[3-(2-hydroxycarbonylethyl) phenyl]-1,2-diphenyl-1,2-ethanediol. The latter process was found to mediate the photoperoxidation of linoleic acid through a type I mechanism, as evidenced by the inhibition produced by the radical scavengers butylated hydroxyanisole and reduced glutathione. The major photoproduct, which contains the benzophenone moiety but lacks the propionic acid side chain, also photosensitized linoleic acid peroxidation. Because lipid peroxidation is indicative of cell membrane lysis, the above findings are highly relevant to explain the photobiological properties of ketoprofen.

Photosensitization by fenofibrate. II. In vitro phototoxicity of the major metabolites

Fenofibric acid, the major metabolite of fenofibrate, was found to be photolabile. Its irradiation in aqueous solution gave rise to two photoproducts, whose formation involves photodecarboxylation of the dissociated acid to an aryloxy-substituted carbanion, which is directly protonated or, alternatively, undergoes a Wittig rearrangement. A comparative in vitro phototoxicity study has been carried out on the anti-hyperlipoproteinemic drug fenofibrate, its metabolites and the photoproducts of fenofibric acid. Fenofibrate, fenofibric acid and its two photoproducts were found to be active when examined by the photohemolysis test and were able to photosensitize peroxidation of linoleic acid, as evidenced by the UV monitoring of dienic hydroperoxides. In summary, the major metabolite of fenofibrate (fenofibric acid), as well as its photoproducts, are phototoxic in vitro. This behavior can be attributed to the fact that the four compounds retain the benzophenone chromophore present in fenofibrate and is indicative of free radical-mediated photosensitization. In agreement with this rationalization, the metabolites with a reduced ketone functionality exhibit no detectable in vitro phototoxicity.