Calcium-induced alteration of mitochondrial morphology and mitochondrial-endoplasmic reticulum contacts in rat brown adipocytes

Mitochondria are key organelles maintaining cellular bioenergetics and integrity, and their regulation of [Ca²⁺]_i homeostasis has been investigated in many cell types. We investigated the short-term Ca-SANDOZ^® treatment on brown adipocyte mitochondria, using imaging and molecular biology techniques. Two-month-old male Wistar rats were divided into two groups: Ca-SANDOZ^® drinking or tap water (control) drinking for three days. Alizarin Red S staining showed increased Ca²⁺ level in the brown adipocytes of treated rats, and potassium pyroantimonate staining localized electron-dense regions in the cytoplasm, mitochondria and around lipid droplets. Ca-SANDOZ^® decreased mitochondrial number, but increased their size and mitochondrial cristae volume. Transmission electron microscopy revealed numerous enlarged and fusioned-like mitochondria in the Ca-SANDOZ^® treated group compared to the control, and megamitochondria in some brown adipocytes. The Ca²⁺ diet affected mitochondrial fusion as mitofusin 1 (MFN1) and mitofusin 2 (MFN2) were increased, and mitochondrial fission as dynamin related protein 1 (DRP1) was decreased. Confocal microscopy showed a higher colocalization rate between functional mitochondria and endoplasmic reticulum (ER). The level of uncoupling protein-1 (UCP1) was elevated, which was confirmed by immunohistochemistry and Western blot analysis. These results suggest that Ca-SANDOZ^® stimulates mitochondrial fusion, increases mitochondrial-ER contacts and the thermogenic capacity of brown adipocytes.

New insights into male (in)fertility: the importance of NO

Infertility is a global problem that is on the rise, especially during the last decade. Currently, infertility affects approximately 10-15% of the population worldwide. The frequency and origin of different forms of infertility varies. It has been shown that reactive oxygen and nitrogen species (ROS and RNS) are involved in the aetiology of infertility, especially male infertility. Various strategies have been designed to remove or decrease the production of ROS and RNS in spermatozoa, in particular during in vitro fertilization. However, in recent years it has been shown that spermatozoa naturally produce a variety of ROS/RNS, including superoxide anion radical (O2 (⋅-)), hydrogen peroxide and NO. These reactive species, in particular NO, are essential in regulating sperm capacitation and the acrosome reaction, two processes that need to be acquired by sperm in order to achieve fertilization potential. In addition, it has recently been shown that mitochondrial function is positively correlated with human sperm fertilization potential and quality and that NO and NO precursors increase sperm motility by increasing energy production in mitochondria. We will review the new link between sperm NO-driven redox regulation and infertility herein. A special emphasis will be placed on the potential implementation of new redox-active substances that modulate the content of NO in spermatozoa to increase fertility and promote conception.

Endothelial cell apoptosis in brown adipose tissue of rats induced by hyperinsulinaemia: the possible role of TNF-α

The aim of the present study was to investigate whether hyperinsulinaemia, which frequently precedes insulin resistance syndrome (obesity, diabetes), induces apoptosis of endothelial cells (ECs) in brown adipose tissue (BAT) and causes BAT atrophy and also, to investigate the possible mechanisms underlying ECs death. In order to induce hyperinsuli-naemia, adult male rats of Wistar strain were treated with high dose of insulin (4 U/kg, intraperitonely) for one or three days. Examinations at ultrastructural level showed apoptotic changes of ECs, allowing us to point out that changes mainly but not exclusively, occur in nuclei. Besides different stages of condensation and alterations of the chromatin, nuclear fragmentation was also observed. Higher number of ECs apoptotic nuclei in the BAT of hyperinsulinaemic rats was also confirmed by propidium iodide staining. Immunohistochemical localization of tumor necrosis factor-alpha (TNF-α) revealed increased expression in ECs of BAT of hyperinsulinaemic animals, indicating its possible role in insulin-induced apoptotic changes. These results suggest that BAT atrophy in hyperinsulinaemia is a result of endothelial and adipocyte apoptosis combined, rather than any of functional components alone.

The role of nitric oxide in remodeling of capillary network in rat interscapular brown adipose tissue after long-term cold acclimation

Cold exposure has been shown to increase blood flow in interscapular brown adipose tissue (IBAT). The aim of the present study was to evaluate the role of the L-arginine-nitric oxide (*NO) pathway on IBAT capillary network remodeling and its possible correlation with superoxide anion radical (O2(*-)). In the rats that received L-arginine (2.25%) or NG-nitro-L-arginine methyl ester (L-NAME, 0.01%) as a drinking liquid and maintained at room (22+/-1 degrees C) or low (4+/-1 degrees C) temperature for 45 days, IBAT capillaries were analyzed by stereology and observed by light and electron microscopy. Additionally, endothelial *NO synthase (eNOS) expression, nitrotyrosine immunoreactivity and both copper zinc superoxide dismutase (CuZnSOD) enzyme activity and immunohistochemical localization were examined. Stereological analyses of IBAT show that the capillary volume density, as well as capillary-to-brown adipocytes ratio, are increased in cold. L-arginine treatment increases, while L-NAME decreases both parameters, compared to respective controls. Those changes were accompanied by capillary dilatation observed by light and electron microscopy. The activity of CuZnSOD is lower in control cold-acclimated rats, as well as in both L-arginine-treated groups, when compared to control animals acclimated to room temperature. L-NAME treatment attenuates the effects both of cold and L-arginine on CuZnSOD and increases immunopositivity for CuZnSOD in room temperature-acclimated rats. Our results show that *NO induces remodeling of the IBAT capillary network by angiogenesis, and presumably that interaction with O2(*-) has a role in that modulation. The increased eNOS expression accompanied by an increased nitrotyrosine immunoreaction observed in both L-arginine-treated groups compared to corresponding controls strengthens this hypothesis.