PITAVASTATIN, a NEW HMG-Coa REDUCTASE INHIBITOR, INDUCES PHOTOTOXICITY in HUMAN KERATINOCYTES

PITAVASTATIN, A NEW HMG-CoA REDUCTASE INHIBITOR, INDUCES PHOTOTOXICITY IN HUMAN KERATINOCYTES NCTC-2544 THROUGH THE FORMATION OF BENZOPHENANTHRIDINE-LIKE PHOTOPRODUCTS

Giampietro Viola*†, Pawel Grobelny§, Maria Antonella Linardi†, Alessia Salvador††, Łukasz Sobotta‡, Jadwiga Mielcarek‡, Francesco Dall’Acqua††Daniela Vedaldi††, and Giuseppe Basso†

†Department of Pediatrics, Oncohematology Laboratory, University of Padova, Italy

§Department of Pharmaceutical Technology, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland

††Department of Pharmaceutical Sciences, University of Padova, Italy

‡Department of Inorganic and Analytical Chemistry, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland

Supporting information

Materials and Methods

Photodegradation spectra

Light absorption spectra were recorded with a Perkin-Elmer Lambda 15 spectrophotometer after irradiation with increasing doses of UVA light. The measurements were carried out with a quartz cuvette containing a solution of pitavastatin in phosphate buffer 10 mM, pH = 7.0.

HPLC analysis. Analytical HPLC was carried out on an Agilent 1200 instrument equipped with a UV-DAD detector. The chromatographic separation was achieved on an octadecylsilane-coated column, 150 mm × 4.6 mm, 5 μm (Gemini, Phenomenex), using ternary gradient elution conditions at a flow rate of 1.0 mL/min as follows: water, solvent A; acetonitrile, solvent B; methanol, solvent C. The gradient conditions were: (a) 75% of A and 25% of B for 0-6 min, (b) linear gradient from 75 to 40% of A, 25% to 40% of B and 0% to 20% of C for 6-7 min and continued till 25 min. Fractions corresponding to PP3 and PP4 respectively, were collected and the solvent evaporated at room temperature using a rotary evaporator.

NMR analysis. The NMR spectra were recorded on a BrukerAvance II (400 MHz) NMR spectrometer, using MeOD as solvent and tetramethylsilane (TMS) as the internal standard.

Assessment of mitochondrial changes and production of reactive oxygen species

The mitochondrial membrane potential was measured with the lipophilic cation 5,5’,6,6’ tetrachlo-1,1’,3,3’-tetraethylbenzimidazol-carbocyanine (JC-1, Molecular Probes Eugene, OR, USA). Briefly, after different times from the irradiation, the cells were collected by centrifugation and resuspended in HBSS containing the JC-1 at a concentration of 2.5 M. The cells were then incubated for 10 min at 37 °C, centrifuged and resuspended again in HBSS. The fluorescence was directly recorded with the flow cytometer (Coulter Cytomics FC500).

The production of Reactive oxygen species (ROS) by flow cytometry using Hydrohethidine (HE) and 2’,7’-dichlorodihydrofluorescein diacetate (H2DCFDA). All of these fluorescent probes were purchased from Molecular Probes (Eugene, OR, USA). After 24 and 48 h from the irradiation, the cells were trypsinized and collected by centrifugation and resuspended in HBSS containing the fluorescence probes HE, or H2DCFDA at the concentration of 2.5 M, and 100nM respectively. As above, the cells were then incubated for 30 min at 37 °C, centrifuged and resuspended again in HBSS. The fluorescence was directly recorded with the flow cytometer using as excitation wavelength 488 nm and emission at 585 nm for HE and at 525 nm for H2DCFDA.

Lysosomal integrity assay

Cells were irradiated in the presence of pitavastatin or the photoproduct and after different times the cells were collected by centrifugation and resuspended in DMEM containing the fluorescent probe LysoTracker RED DND-99 (Molecular Probes) at the concentration of 50 nM and incubated for 30 min at 37 °C. After this period the cells were washed and analyzed by flow cytometry.

Table S1. Nuclear magnetic resonance data of photoproducts PP3 and PP4.

PP3 /
PP4
1H (J) / 13C / 1H (J) / 13C
1 / 8.01 d (8.4) / 128.36 / 8.11d (1.2) / 130.07
2 / 7.69 t (7.6) / 130.23 / 7.75m / 129.59
3 / 7.53 t (7.6) / 127.36 / 7.67m / 127.14
4 / 8.33 d (8.4) / 126.49 / 8.91d (8.4) / 128.05
5 / - / 124.59 / - / 124.57
6 / - / 147.11 / - / 146.90
7 / - / 161.10 / - / 162.24
8 / - / 131.98 / - / 125.73
9 / 3.05t (6.3) / 25.44 / 8.62 (2.71) / 125.00
10 / 2.89d (6.3) / 29.63 / 8.07m / 128.84
11 / - / 144.69 / - / 138.09
12 / 7.22m / 115.83 / 7.81dd (9.4; 2.7) / 113.14
13 / - / 163.17 / - / 162.24
14 / 7.14m / 114.11 / 7.57m / 116.98
15 / 7.90m / 132.61 / 9.17dd (9.4; 5.5) / 132.50
16 / - / 129.30 / - / 127.14
17 / 2.40m / 15.59 / 2.89tt(8.3; 5.0) / 15.65
18 / 1.14t (8.6) / 9.03 / 1.31m / 9.19
19 / 1.19t (7.7) / 9.03 / 1.20m / 9.19
20 / - / 141.51 / - / 132.78

Chemical shift values are given in ppm, J expressed in Hz.

Figure S1

HPLC analysis of the crude mixture after the photodegradation of pitavastatin in aqueous solution showing the separation of investigated photoproducts. The elution profile was monitored at 250 (red line) and 280 nm (black line).The inset in the chromatogram represents absorption spectra.

Figure S2

Photodegradation spectra of PP3 and PP4

Figure S3

Determination of the mode of cell death using Annexin-V and PI staining and flow cytometric analysis. Representative biparametric histograms obtained after 24 and 48 h after the irradiation (3.75 J cm-2) of human keratinocytes NCTC-2544 in the presence of PIT 50 and PP4 10 M.

Figure S4

Panel A shows the percentage of cell with low mitochondrial potential after 24 and 48 h from the irradiation (3.75 J cm-2) in the presence of PIT and PP4. Panels B and C show the mitochondrial production of ROS evaluated by flow cytometry using the fluorescent probe HE (panel B) and H2DCFDA (Panel D). Data are expressed as mean  S.E.M. of three independent experiments.

Figure S5

Percentage of cells with reduced Lysotracker fluorescence. NCTC-2544 cells were irradiated in the presence of PIT or PP4 and after the indicated times stained with LysoTracker RED and analyzed by flow cytometry, Data are expressed as mean  S.E.M. of three independent experiments