Drug–Drug Interactions within Protein Cavities Probed by Triplet–Triplet Energy Transfer

A new direct and noninvasive methodology based on transient absorption spectroscopy has been developed to probe the feasibility of drug–drug interactions within a common protein binding site. The simultaneous presence of (<i>R</i>)-cinacalcet (CIN) and (<i>S</i>)-propranolol (PPN) within human or bovine α₁-acid glycoproteins (AAGs) is revealed by detection of ³CIN* as the only transient species after laser flash photolysis of CIN/PPN/AAG mixtures at 308 nm. This is the result of triplet–triplet energy transfer from ³PPN* to CIN, which requires close contact between the two drugs within the same biological compartment. Similar results are obtained with nabumetone and CIN as donor/acceptor partners. This new methodology can, in principle, be extended to a variety of drug/drug/biomolecule combinations

Mechanistic Studies on the Photoallergy Mediated by Fenofibric Acid: Photoreactivity with Serum Albumins

The photoreactivity of fenofibric acid (FA) in the presence of human and bovine serum albumins (HSA and BSA, respectively) has been investigated by steady-state irradiation, fluorescence, and laser flash photolysis (LFP). Spectroscopic measurements allowed for the determination of a 1:1 stoichiometry for the FA/SA complexes and pointed to a moderate binding of FA to the proteins; by contrast, the FA photoproducts were complexed more efficiently with SAs. Covalent photobinding to the protein, which is directly related to the photoallergic properties of the drug, was detected after long irradiation times and was found to be significantly higher in the case of BSA. Intermolecular FA-amino acid and FA-albumin irradiations resulted in the formation of photoproducts arising from coupling between both moieties, as indicated by mass spectrometric analysis. Mechanistic studies using model drug–amino acid linked systems indicated that the key photochemical step involved in photoallergy is formal hydrogen atom transfer from an amino acid residue to the excited benzophenone chromophore of FA or (more likely) its photoproducts. This results in the formation of caged radical pairs followed by C–C coupling to give covalent photoaducts

Photophysical Probes To Assess the Potential of Cholic Acid Aggregates as Drug Carriers

The two enantiomers of the nonsteroidal antiinflammatory drug naproxen and of its methyl ester have been selected as representative probes with markedly different hydrophobicity to assess the potential of cholic acid aggregates as drug carriers by means of photophysical techniques. The different distribution of the probes between bulk solution and aggregates has been assessed by quenching of their singlet and triplet excited states by iodide and nitrite anions, respectively. This straightforward photophysical methodology can, in principle, be extended to a variety of drugs containing a photoactive chromophore

TLR expression on moDC without or with stimuli.

<p><b>A</b>) RT-PCR analysis for mRNA expression of different TLRs on imDC from a representative DTH patient. <b>B</b>) Bars represent the median fold increase in TLR2, 4, 7 and 8 expression and MyD88 after stimulation with AX, PAM, LPS and R848 alone or in combination on DC from DTH patients (left) and controls (right). *p<0.05, **p<0.01, ***p<0.001.</p

DC maturation and lymphocyte proliferation after different stimuli.

<p><b>A</b>) Changes in CD86 expression on moDC after stimulation with AX alone or in combination with PAM, LPS or both (left) and with AX alone or in combination with R848 (right). <b>B</b>) Bars represent the percentage of positive cases of DC maturation after stimulation with AX, PAM, LPS and R848 alone or in combination in DC from DTH patients (N=15) (black bars) and controls (N=15) (grey bars). *, p<0.05, represents the significant differences after statistical comparisons (χ² analysis) in the percentage of cases comparing DTH patients to controls. <b>C</b>) Changes in CD3⁺ T-lymphocyte proliferation after stimulation with AX alone or in combination with PAM, LPS or both (left) and with AX alone or in combination with R848 (right). Histograms are representative of one DTH patient. <b>D</b>) Bars represent the percentage of positive cases of LTT after stimulation with AX, PAM, LPS and R848 alone or in combination in T cells from DTH patients (N=15) (black bars) and controls (N=15) (grey bars). *, p<0.05, represents the significant differences after statistical comparisons (χ² analysis) in the percentage of cases comparing DTH patients to controls.</p