Second harmonic generation confocal microscopy of collagen type I from rat tendon cryosections

We performed second harmonic generation (SHG) imaging of collagen in rat-tendon cryosections, using femtosecond laser scanning confocal microscopy, both in backscattering and transmission geometries. SHG transmission images of collagen fibers were spatially resolved due to a coherent, directional SHG component. This effect was enhanced with the use of an index-matching fluid (n(l) 1.52). The average SHG intensity oscillated with wavelength in the backscattered geometry (isotropic SHG component), whereas the spectral profile was consistent with quasi-phase-matching conditions in transmission geometry (forward propagating, coherent SHG component) around 440 nm (lambda(p) 880 nm). Collagen type I from bovine Achilles tendon was imaged for SHG in the backscattered geometry and its first-order effective nonlinear coefficient was determined (vertical bar d(eff)vertical bar approximate to 0.085(+/- 0.025) x 10-(12)mV(-1)) by comparison to samples of inorganic materials with known effective nonlinear coefficients (LiNbO3 and LiIO3). The SHG spectral response of collagen type I from bovine Achilles tendon matched that of the rat-tendon cryosections in backscattered geometry. Collagen types I, II, and VI powders (nonfibrous) did not show any detectable SHG, indicating a lack of noncentrosymmetric crystalline structure at the molecular level. The various stages of collagen thermal denaturation were investigated in rat-tendon cryosections using SHG and bright-field imaging. Thermal denaturation resulted in the gradual destruction of the SHG signal

Organometallic rhenium complexes divert doxorubicin to the mitochondria

Doxorubicin, a well-established chemotherapeutic agent, is known to accumulate in the cell nucleus. By using ICP-MS, we show that the conjugation of two small organometallic rhenium complexes to this structural motif results in a significant redirection of the conjugates from the nucleus to the mitochondria. Despite this relocation, the two bioconjugates display excellent toxicity toward HeLa cells. In addition, we carried out a preliminarily investigation of aspects of cytotoxicity and present evidence that the conjugates disrupt the mitochondrial membrane potential, are strong inhibitors of human Topoisomerase II, and induce apoptosis. Such derivatives may enhance the therapeutic index of the aggressive parent drug and overcome drug resistance by influencing nuclear and mitochondrial homeostasis

Alterations in Dysadherin Expression and F-Actin Reorganization: A Possible Mechanism of Hypericin-Mediated Photodynamic Therapy In Colon Adenocarcinoma Cells

Dysadherin is a recently found anti-adhesion molecule, therefore detection and down regulation of its expression is promising in cancer treatment. The up-regulation of dysadherin contributes to colon cancer recurrence and metastasis. Dysadherin also has connections with cytoskeletal proteins and it can cause alterations in the organisation of filamentous actin (F-actin) in metastatic cancers. In this study, hypericin (HYP)-mediated photodynamic therapy (PDT) was performed in two different grade colon adenocarcinoma cell lines HT-29 (Grade I) and Caco-2 (Grade II). Cells were treated with 0.04, 0.08 or 0.15 mu M HYP concentrations and irradiated with (4 J/cm(2)) fluorescent lamps. The effects of HYP was examined 16 and 24 h after the activation. We investigated for the first time the effect of HYP-mediated PDT on the expression of dysadherin and F-actin organisation. According to the results, HYP mediated PDT caused a decrease in gene expression and immunofluorescence staining of dysadherin and an increase in actin stress fibers and actin aggregates in HT-29 and Caco-2 cell lines. Besides, cytotoxicity, number of floating cells and apoptotic index changed depending on the cell type, HYP concentration and incubation time. We have demonstrated for the first time that dysadherin and F-actin could be target molecules for HYP-mediated PDT in HT-29 and Caco-2 colon cancer cell lines.Wo