Mitochondrial OXPHOS function is unaffected by chronic azithromycin treatment

Azithromycin inhibits glioblastoma angiogenesis in mice via inducing mitochondrial dysfunction and oxidative stress

The poor outcomes in glioblastoma (GBM) necessitate new treatments. As GBM is highly vascularized and its growth is largely dependent on angiogenesis, angiogenesis inhibitors have been hotly evaluated in clinical trials for GBM treatment for the last decade. In line with these efforts, our work reveals that azithromycin, a clinically available antibiotic, is a novel angiogenesis inhibitor. Azithromycin inhibits vessel structure formation on Matrigel of GBM-derived endothelial cell (ECs) and other types of ECs. Time course analysis shows that azithromycin interferes with the early stage of angiogenesis. Azithromycin also inhibits GBM-derived EC adhesion, growth and survival but not migration. The transgenic zebrafish Tg (fli1a: EGFP) model clearly shows that azithromycin inhibits angiogenesis in vivo. Of note, azithromycin at non-toxic dose inhibits GBM growth in mice and increases overall survival, and furthermore, this is associated with angiogenesis inhibition. Mechanism studies show that azithromycin decreases mitochondrial respiration by suppressing the activity of multiple complexes, leading to ATP reduction, oxidative stress and damage. In addition, oxidative stress induced by azithromycin is through thiol redox-mediated pathways. Our work demonstrates the anti-angiogenic activity of azithromycin via inducing mitochondrial dysfunction and oxidative stress. Our pre-clinical evidence provides a rationale for initiating clinical trials using azithromycin in combination with standard-of-care drugs for GBM patients.

Side effects of antibiotics and perturbations of mitochondria functions

Antibiotics are one of the greatest discoveries of medicine of the past century. Despite their invaluable contribution to infectious disease, their administration could lead to side effects that in some cases are serious. The toxicity of some antibiotics is in part due to their interaction with mitochondria: these organelles derive from a bacterial ancestor and possess specific translation machinery that shares similarities with the bacterial counterpart. In other cases, the antibiotics could interfere with mitochondrial functions even if their main bacterial targets are not shared with the eukaryotic cells. The purpose of this review is to summarize the effects of antibiotics administration on mitochondrial homeostasis and the opportunity that some of these molecules could represent in cancer treatment. The importance of antimicrobial therapy is unquestionable, but the identification of interaction with eukaryotic cells and in particular with mitochondria is crucial to reduce the toxicity of these drugs and to explore other useful medical applications.

Cytochrome c Oxidase Activity as a Metabolic Regulator in Pancreatic Beta-Cells

Pancreatic β-cells couple glucose-stimulated insulin secretion (GSIS) with oxidative phosphorylation via cytochrome c oxidase (COX), a mitochondrial respiratory-chain enzyme. The Cohen diabetic-sensitive (CDs) rats exhibit hyperglycemia when fed a diabetogenic diet but maintain normoglycemia on a regular diet. We have previously reported a decreased COX activity in CDs rats and explored its relevance for type 2 diabetes (T2D). In this study, we investigated the relation between COX activity in islets, peripheral-blood mononuclear cells (PBMCs), and GSIS during diabetes development in CDs rats fed a diabetogenic diet for 4, 11, 20, and 30 days and during reversion to normoglycemia in hyperglycemic CDs rats fed a reversion diet for 7, 11, and 20 days. An oral glucose-tolerance test was performed at different periods of the diets measuring blood glucose and insulin concentrations. COX activity was determined in islets and PBMCs isolated from rats at the different periods of the diets. We demonstrated a progressive reduction in COX activity in CDs-islets that correlated positively with the decreasing GSIS (R2 = 0.9691, p < 0.001) and inversely with the elevation in blood glucose levels (R2 = 0.8396, p < 0.001). Hyperglycemia was initiated when islet COX activity decreased below 46%. The reversion diet restored >46% of the islet COX activity and GSIS while re-establishing normoglycemia. Interestingly, COX activity in PBMCs correlated significantly with islet COX activity (R2 = 0.8944, p < 0.001). Our data support islet COX activity as a major metabolic regulator of β-cells function. The correlation between COX activity in PBMCs and islets may serve as a noninvasive biomarker to monitor β-cell dysfunction in diabetes.

Therapeutic Effects of Azithromycin on Spinal Cord Injury in Male Wistar Rats: A Role for Inflammatory Pathways

BACKGROUND

 Inflammatory responses, including macrophages/microglia imbalance, are associated with spinal cord injury (SCI) complications. Accumulating evidence also suggests an anti-inflammatory property of azithromycin (AZM).

MATERIAL AND METHODS

 Male Wistar rats were subjected to T9 vertebra laminectomy. SCI was induced by spinal cord compression at this level with an aneurysmal clip for 60 seconds. They were divided into three groups: the sham-operated group and two SCI treatment (normal saline as a vehicle control vs. AZM at 180 mg/kg/d intraperitoneally for 3 days postsurgery; first dose: 30 minutes after surgery) groups. Locomotor scaling and behavioral tests for neuropathic pain were evaluated and compared through a 28-day period. At the end of the study, tissue samples were taken to assess neuroinflammatory changes and neural demyelination using ELISA and histopathologic examinations, respectively. In addition, the proportion of M1/M2 macrophage polarization was assessed by using flow cytometry.

RESULTS

 Post-SCI AZM treatment (180 mg/kg/d for 3 days) significantly improved locomotion (p < 0.01) and decreased sensitivity to mechanical (p < 0.01) and thermal allodynia (p < 0.001). Moreover, there was a significant tumor necrosis factor-α (TNF-α) decline (p < 0.01) and interleukin-10 (IL-10) elevation (p < 0.01) in the spinal cord tissue of the AZM-treated group compared with the control groups 28 days post-SCI. AZM significantly improved neuroinflammation as evidenced by reduction of the M1 expression, elevation of M2 macrophages, and reduction of the M1/M2 ratio in both the dorsal root ganglion and the spinal cord tissue after SCI compared with controls (p < 0.01).

CONCLUSION

 AZM treatment can be considered a therapeutic agent for SCI, as it could reduce neuroinflammation and SCI sensory/locomotor complications.

Analyzing mitochondrial function in human peripheral blood mononuclear cells

Mitochondrial oxidative phosphorylation (OXPHOS) is responsible for producing most of the adenosine triphosphate required by eukaryotic cells. Lymphocytes make up the majority of the peripheral blood mononuclear cells. Peripheral blood mononuclear cells are readily obtainable, providing an ideal sample to monitor systemic changes and understand molecular signaling mechanisms in disease processes. Mitochondrial energy metabolism of lymphocyte has been used to screen for OXPHOS disorders. While there are increasing studies of lymphocyte OXPHOS, few studies examined activity of electron transport chain of lymphocyte mitochondria. We present an optimal protocol to harvest fresh peripheral blood mononuclear cells from human whole blood, determine integrated mitochondrial function, and analyze electron transport chain complex activity. Analyzing integrated mitochondrial function using OXPHOS provides data to uncover defects in the transport of substrates into the mitochondria, generation of reducing equivalents, the electron transport chain, and coupling to the production of adenosine triphosphate. The optimal conditions to harvest peripheral blood mononuclear cells were using blood anticoagulated with ethylenediaminetetraacetic acid, processed utilizing Lymphoprep™, and washed in phosphate buffered saline, all at room temperature. Using isolated peripheral blood mononuclear cells, integrated mitochondrial function and the activities of electron transport chain were determined.

Evaluating the therapeutic potential of idebenone and related quinone analogues in Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is an important cause of mitochondrial blindness among young adults. In this study, we investigated the potential of four quinone analogues (CoQ₁, CoQ₁₀, decylubiquinone and idebenone) in compensating for the deleterious effect of the m.11778G>A mitochondrial DNA mutation. The LHON fibroblast cell lines tested exhibited reduced cell growth, impaired mitochondrial bioenergetics and elevated levels of reactive oxygen species (ROS). Idebenone increased ATP production and reduced ROS levels, but the effect was partial and cell-specific. The remaining quinone analogues had variable effects and a negative impact on certain mitochondrial parameters was observed in some cell lines.

The Effects of Ascorbate, N-Acetylcysteine, and Resveratrol on Fibroblasts from Patients with Mitochondrial Disorders

Reactive oxygen species (ROS) are assumed to be implicated in the pathogenesis of inborn mitochondrial diseases affecting oxidative phosphorylation (OXPHOS). In the current study, we characterized the effects of three small molecules with antioxidant properties (N-acetylcysteine, ascorbate, and resveratrol) on ROS production and several OXPHOS parameters (growth in glucose free medium, ATP production, mitochondrial content and membrane potential (MMP)), in primary fibroblasts derived from seven patients with different molecularly defined and undefined mitochondrial diseases. N-acetylcysteine appeared to be the most beneficial compound, reducing ROS while increasing growth and ATP production in some patients' cells. Ascorbate showed a variable positive or negative effect on ROS, ATP production, and mitochondrial content, while incubation with resveratrol disclosed either no effect or detrimental effect on ATP production and MMP in some cells. The individual responses highlight the importance of investigating multiple parameters in addition to ROS to obtain a more balanced view of the overall effect on OXPHOS when evaluating antioxidant treatment options for mitochondrial diseases.