Damage targeted to the mitochondrial interior induces autophagy, cell cycle arrest and, only at high doses, apoptosis.

It is generally accepted that permeabilization of the outer mitochondrial membrane is a crucial event in the induction of apoptosis. In order to know how the cell would respond to the damage targeted not to the outer mitochondrial membrane, but to the mitochondrial interior, we followed the changes in cell morphology and some biochemical parameters triggered by ROS in the mitochondrial inner space. The experiments were carried out in epidermoid carcinoma A431 cells. For stimulated production of singlet oxygen in the inner space of mitochondria, we employed photodynamic treatment (PDT) mediated by a cationic photosensitizer 7-diamino-2,8-dimethyl-5-phenylphenazinium chloride (Safranin O, Safr), accumulating in the inner space of mitochondria. At low to intermediate cytotoxic doses (up to CD50 reducing cellular viability by 50%), Safr-PDT did not reveal hallmarks of dead cells, and the decrease of cellular viability could be attributed to cell cycle inhibition, and enhanced autophagy. High Safr-PDT doses (beyond CD70) did induce cell death by apoptosis involving release of cytochrome c and caspase-3 activation, in addition to enhanced autophagy.

Apoptosis, autophagy and cell cycle arrest following photodamage to mitochondrial interior.

Cell death induced by oxidative insult targeted to mitochondrial interior of A431 cells was investigated. For stimulated production of ROS in the inner space of mitochondria, safranin-mediated photodynamic treatment (PDT) was employed. Another photosensitizer, mTHPC, which diffusely localizes to cellular membranes, was used for comparison. Cell response to the oxidative insult in mitochondrial interior was different from the response to the photodamage produced in cellular membranes. Autophagy and apoptotic features of cell death in response to mTHPC-PDT was observed in a wide range of PDT doses. Cell response to the oxidative stress in mitochondrial interior was dose-dependent. Damage up to CD50 did not reveal hallmarks of dead cells. At intermediate damage (CD50), cells manifested enhanced autophagy and reduced population of S-phase, but not apoptosis. Severe damage (beyond CD70) induced apoptosis following release of cytochrome c and caspase activation, in addition to autophagy and cell cycle arrest.

[Expression of matrix metalloproteinases in patients with malignant tumors]. / Matrikso metaloproteinazes sergant piktybiniais navikais.

The cancer cells secrete proteolytic enzymes, which are important in the tumor spreading. The cells must cross basement membrane and extracellular matrix barriers in order to spread. The matrix metalloproteinases are a family of endopeptidases, which enzymatic activity depends on the presence of zinc ion in the catalytic domain. Matrix metalloproteinases hydrolyze extracellular matrix components such as collagen, laminin, fibronectin, proteoglycans and contribute to the spreading of tumor cells by eliminating the surrounding extracellular matrix and basement membrane barriers. This review describes matrix metalloproteinases family classification and structure, their role under physiological conditions and induced proteolysis during pathological processes. There is a balance between proteolytic extracellular matrix degradation and proteolysis inhibition, but under pathological state (e. g. tumor development) the proteolysis becomes uncontrolled. We review tissue inhibitors of matrix metalloproteinases and synthetic matrix metalloproteinase inhibitors, their perspective in cancer treatment; as well as different matrix metalloproteinases expression in patients with tumors and its prognostic significance during cancer progression.

Correlation of death modes of photosensitized cells with intracellular ATP concentration.

The impact of intensity of glycolysis and oxidative phosphorylation on death of photosensitized murine hepatoma MH22 cells in vitro has been investigated. Cells photosensitized with meso-tetra(4-sulfonatophenyl)-porphine localized to lysosomes died mostly by necrosis, and the mode of cell death did not depend on the energy metabolism. Photosensitization with 5-aminolevulinic acid-stimulated endogenous porphyrins localized mainly in mitochondria or 5,10,15,20-tetrakis(m-hydroxyphenyl)-chlorine localized to cell membranes, including mitochondria, led to cell death mostly by apoptosis. In this case, the mode of cell death depended on the medium: under conditions unfavorable to glycolysis the ratio apoptosis/necrosis decreased significantly.