Vascular-adrenal niche--endothelial cell-mediated sensitization of human adrenocortical cells to angiotensin II.

Alterations in both vasculature and renin-angiotensin-aldosterone system are a consistent finding in the metabolic syndrome. Adrenal tissue is highly vascularized and encounters blood flow, exceeding by far the volume expected for its size. Endothelial cells in the adrenal vasculature are therefore a major cellular component of adrenocortical tissue. The aim of the study was to analyze the cellular interaction between endothelial and steroid producing cells, focusing on endothelial cell-factor-mediated activation of aldosterone synthesis. The interaction between human endothelial (HUVECs) cell-conditioned medium and human adrenocortical (NCI-H295R) cells IN VITRO induced a significant surge in aldosterone secretion. The endothelial cell-conditioned medium together with angiotensin II and forskolin also potentiated aldosterone release by 1.5-fold and 2.6-fold, respectively, while preincubation of NCI-H295R cells for 24 h with endothelial cell-conditioned medium enhanced and sensitized the response of NCI-H295R to subsequent angiotensin II and forskolin stimuli by 2.5-fold and 2.2-fold, respectively. The increase in aldosterone release after preincubation with endothelial cell-conditioned medium was sensitive to cycloheximide and KN-93. Cellular conditioning with endothelial-cell factors exerts a hitherto unknown paracrine regulation of aldosterone production in human adrenocortical cells. This interaction may contribute to altered basal aldosterone release and have a role in patients with hypertension.

Collagen type I prevents glyoxal-induced apoptosis in osteoblastic cells cultured on titanium alloy.

Advanced glycation end products (AGEs) irreversibly cross-link proteins with sugars and accumulate at a higher age and in diabetes, processes which can interfere with the integration of implants into the tissue. Glyoxal is a highly reactive glycating agent involved in the formation of AGEs and is known to induce apoptosis, as revealed by the upregulation of caspase-3 and fractin (caspase-3 being a key enzyme activated during the late stage of apoptosis and fractin being a caspase-cleaved actin fragment). In this study, we investigated the influence of collagen type I coating on the cytotoxic effect of glyoxal on rat calvarial osteoblastic cells and on human osteosarcoma cells (Saos-2) grown on titanium alloy, Ti6Al4V. Activation of caspase-3 and fractin was measured by counting immunohistochemically stained cells and by flow cytometry with propidium iodide (detection of the apoptosis indicating a sub-G1 peak). Our results showed an increased number of apoptotic osteoblasts after incubation with glyoxal on Ti6Al4V discs. However, the number of apoptotic cells on collagen-coated titanium was significantly smaller than on uncoated titanium after the same treatment. The present findings demonstrate that osteoblasts treated with glyoxal undergo apoptosis, whereas collagen type I coating of titanium alloys (used for implants) has an antiapoptotic function.

Coenzyme Q10 reduces the toxicity of rotenone in neuronal cultures by preserving the mitochondrial membrane potential.

Defects in mitochondrial energy metabolism due to respiratory chain disorders lead to a decrease in mitochondrial membrane potential (DeltaPsim) and induce apoptosis. Since coenzyme Q10 (CoQ10) plays a dual role as an antioxidant and bioenergetic agent in the respiratory chain, it has attracted increasing attention concerning the prevention of apoptosis in mitochondrial diseases. In this study the potential of CoQ10 to antagonize the apoptosis-inducing effects of the respiratory chain inhibitor rotenone was explored by video-enhanced microscopy in SH-SY5Y neuroblastoma cells. The cationic fluorescent dye JC-1 which exhibits potential-dependent accumulation in mitochondria was used as an indicator to monitor changes in DeltaPsim. The relative changes in fluorescence intensity after incubation with rotenone for 15 minutes were calculated. Pre-treatment with CoQ10 (10 or 100 microM) for 48 h led to a significant reduction of rotenone-induced loss of DeltaPsim. These results suggest, that cytoprotection by CoQ10 may be mediated by raising cellular resistance against the initiating steps of apoptosis, namely the decrease of DeltaPsim. Whether these data may provide new directions for the development of neuroprotective strategies has to be investigated in future studies.

Intracellular changes in astrocytes and NG 108-15 neuroblastoma X glioma cells induced by advanced glycation end products.

INTRODUCTION: The extracellular effects caused by advanced glycation end products (AGEs) themselves formed by the Maillard-reaction from proteins and sugars, are well known. Less is known about the effects of AGEs on cellular function. Cellular dysfunctions accumulate with increasing age and can be found as a pathogenetic principle of different diseases where AGEs are involved. The causal mechanisms of these cellular dysfunctions are not fully understood. MATERIAL AND METHODS: AGEs effects were examined in cell culture using video microscopy, immunohistochemistry, flow cytometry and biochemical methods in neural (NG 108-15) and glial (primary culture of astrocytes) cells. RESULTS: AGEs can bind to the cell surface of neural and glial cells. AGEs induce an altered distribution of vesicles and a statistically significant reduction in the velocity of microvesicles. The proteins dynamin 2 and clathrin, which are an important part of the transport apparatus, show changes in intracellular distribution similar to that of microvesicles. The immunoreactivity of dynamin 2 in AGE-treated cells is increased after AGE-incubation. After incubation durations of 2 h, 6 h and 12 h we found an increase (maximum +34.6%) of the relative fluorescence intensities of dynamin 2 in the AGE-BSA treated cells in comparison to the control cells (BSA). Using flow cytometry we found a minimal increase (14.4%) in clathrin immunoreactivity after 2 h incubation with 500 nM AGE-BSA. The non-quantitative western blot showed no difference of the electrophoretic behaviour of both dynamin 2 and clathrin in AGE-BSA-incubated cells (2 h, 500 nM) and in control cells (2 h, 500 nM BSA-incubation). The incubation with AGE-BSA up to a concentration of 500 nM in culture was not followed by apoptotic or necrotic cell death. DISCUSSION: We could show defined effects on the cells induced by incubation with AGEs. One of the effects is a significant reduction of the velocity of microvesicles, the reason for this is unclear. It could be due to disturbed calcium metabolism or caused by microtubuli-changes. The aggregation of intracellular microvesicles could be the result of an altered binding-behaviour of the vesicles or the destruction of the transport apparatus. The proteins dynamin 2 and clathrin, which are involved in transport apparatus, show changes in intracellular distribution indicating a breakdown of the normal cellular distribution system. The current results may contribute to the understanding of the pathologic processes in the cell in Mb. Alzheimer and other neurodegenerative diseases, where AGEs-accumulation can be found in tissues.