Mitochondrial Electron Transport Chain Complex II Dysfunction Causes Premature Aging of Hematopoietic Stem Cells.

Mitochondria are indispensable in maintaining hematopoietic stem cells (HSCs), and mitochondrial complex II (MCII) has been recognized as a key component of HSCs. However, the physiological role of MCII on long-term hematopoiesis and hematopoietic reconstitution capacity remains unknown. Hence, this study evaluated the impact of MCII dysfunctions on long-term HSC maintenance and hematopoietic homeostasis among conditional transgenic mice with a missense mutation in the succinate dehydrogenase complex subunit C gene (SdhcV69E). HSCs collected from SdhcV69E mice had a higher reactive oxygen species (ROS) accumulation and DNA damage in response to mitochondrial activation. Via the aging stress response, MCII dysfunctions caused decreased white blood cell count with myeloid-skewing property, macrocytic anemia, and thrombocytosis. Moreover, the HSCs of aged SdhcV69E mice exhibited greater ROS accumulation and lower membrane potential. Transplantation-induced replicative stress also caused premature senescent hematopoiesis. Furthermore, accelerated ROS accumulation and profound DNA damage in HSCs were observed in the SdhcV69E-derived cell recipients. The long-term hematopoietic reconstitution capacity was remarkably impaired in HSCs from the SdhcV69E-derived cell recipients. Taken together, MCII plays an essential role in long-term hematopoiesis, and MCII dysfunctions with aging or replicative stresses caused excessive ROS accumulation and DNA damage in HSCs, leading to premature senescence.

Development of an Analytical Method for Unsaturated Disaccharides from Heparan Sulfate Using Dansylhydrazine Derivatization and High-Performance Liquid Chromatography with Fluorescence Detection.

Glycosaminoglycans (GAGs), such as heparan sulfate (HS), play essential roles in living organisms. Understanding the functionality of HS and its involvement in disease progression necessitates the sensitive and quantitative detection of HS-derived unsaturated disaccharides. Conventionally, fluorescence derivatization precedes the HPLC analysis of these disaccharides. However, the presence of excess unreacted derivatization reagents can inhibit rapid and sensitive analysis in chromatographic determinations. In this study, we describe analytical methods that use dansylhydrazine as a derivatization agent for the detection and determination of HS-derived unsaturated disaccharides using HPLC. In addition, we have developed a straightforward method for removing excess unreacted reagent using a MonoSpin NH2 column. This method may be employed to remove excess pre-labeling reagents, thereby facilitating the analysis of HS-derived unsaturated disaccharides with satisfactory reproducibility.

The role of nutrition and oxidative stress as aging factors in Caenorhabditis elegans.

The molecular mechanism of aging, which has been a "black box" for many years, has been elucidated in recent years, and the nematode C. elegans, which is a model animal for aging research, has played a major role in its elucidation. From the analysis of C. elegans longevity-related mutant genes, many signal transduction systems, with the insulin/insulin-like growth factor signal transduction system at the core, have emerged. It has become clear that this signal transduction system is greatly affected by external nutrients and is involved in the downstream regulation of oxidative stress, which is considered to be one of the main causes of aging.

A Study of Morphological Changes in Renal Afferent Arterioles Induced by Angiotensin II Type 1 Receptor Blockers in Hypertensive Patients.

BACKGROUND: Renin-angiotensin-aldosterone system blockers are known to reduce hypertrophy of vascular smooth muscle cells (SMCs) in hypertensive cases. However, we have reported marked proliferative changes of renal afferent arteriolar SMCs in rats induced by a long-term administration of angiotensin II type 1 receptor blockers (ARBs) and an angiotensin-converting enzyme inhibitor (ACEI). In this study, we examined the morphological changes of afferent arteriolar walls in human kidneys with or without ARBs/ACEIs. METHODS: Forty-four wedge resections were taken from patients aged 45-74 years from 92 nephrectomized kidneys due to malignancy at Toho University Omori Medical Center between 2013 and 2016. They were divided into the following three groups: 18 hypertensive patients treated with antihypertensive agents including ARBs or ACEIs (the HTARB group), 6 hypertensive patients treated with calcium channel blockers without ARBs/ACEIs (the HTCCB group), and 20 normotensive patients (the normotensive group) as a control. Cases expecting vascular changes such as diabetes were excluded. In each case renal arterioles were measured as the ratio of inner/outer arteriolar diameter, and pathologists estimated morphological abnormal changes, scoring each specimen independently. RESULTS: The ratio in the HTARB group was 0.39 ± 0.05 (mean ± SD), and was significantly the lowest among the three groups (0.46 ± 0.02 in the HTCCB, 0.53 ± 0.02 in the normotensive group; p = 0.0107 vs. HTCCB, p = 0.00001 vs. normotensive). The ratio in the three groups significantly correlated with the estimated glomerular filtration rate (r = 0.4915, p < 0.0007). The afferent arteriolar SMCs in the HTARB group frequently showed marked proliferative and irregular changes. The score of SMC abnormalities estimated regarding the proliferation, irregularity of the arrangement, and size in hilar afferent arteriolar SMCs was highest in the HTARB group and showed statistical significance (p = 0.0088, p = 0.00001, and p = 0.025 versus other two groups). CONCLUSIONS: We consider that these morphological changes in arterioles are induced by ARBs/ACEIs. These changes could induce an important suppression of glomerular hyperfiltration and could lead to glomerular ischemia. However, the clinical consequences of these morphological changes in correlation with ARBs/ACEIs were not sufficiently clear and require further analysis. We should consider renal arteriolar morphological changes when using ARBs/ACEIs.

Sex difference in clinical presentation of patients with infectious mononucleosis caused by Epstein-Barr virus.

INTRODUCTION: There are few studies on sex difference in patients with infectious mononucleosis caused by Epstein-Barr virus (EBV-IM). We performed a retrospective study to evaluate the sex difference in clinical presentation of patients with EBV-IM. METHODS: We performed a single-center retrospective study evaluating >14-year-old patients with serologically confirmed EBV-IM during 2006-2017. We compared the patients' age, symptoms, physical findings, and laboratory data between male and female patients. To adjust for confounding factors, we performed a logistic regression analysis based on the results of univariate comparisons. RESULT: Of the 122 eligible patients (56 male and 66 female, ratio: 1:1.2), the median ages were 26 years old (interquartile range [IR], 22-31.5 years old]) and 22 years old (IR, 20-25 years old) for males and females, respectively (p < 0.001). Headache was significantly more prevalent in males (25.0% vs. 10.6%, p = 0.036). Leukocyte count was also significantly higher in males (11,400/mm3 [IR, 7,600-14,100/mm3] vs. 9,400/mm3 [IR, 6,600-11,600/mm3], p = 0.021). The prevalence of periorbital edema (male: 3.6% vs. female: 18.1%, p = 0.012) and severity of transaminase elevation were significantly higher in females. The regression analysis evaluating clinical characteristics of male patients showed that age >30 years old, headache, and leukocyte >11,000/mm3 had high odds ratios. CONCLUSION: Our single-center retrospective study suggests that older age of onset, headache, and leukocytosis are more likely to be characteristics of male patients with EBV-IM. Our study also underscores the importance of periorbital edema as a clue for early diagnosis of EBV-IM, especially in female patients.

Clinical differentiation of infectious mononucleosis that is caused by Epstein-Barr virus or cytomegalovirus: A single-center case-control study in Japan.

INTRODUCTION: Infectious mononucleosis (IM) is a common viral infection that typically causes fever, pharyngitis, and lymphadenopathy in young patients. The Epstein-Barr virus (EBV) is the most common cause of IM, followed by cytomegalovirus (CMV). Given that serological testing is associated with limitations regarding its accuracy, availability, and time to receive results, clinical differentiation based on symptoms, signs, and basic tests would be useful. We evaluated whether clinical findings could be used to differentiate EBV-IM from CMV-IM. METHODS: In this single-center retrospective case-control study, we evaluated >14-year-old patients with serologically confirmed EBV-IM or CMV-IM during 2006-2017. We compared the patients' symptoms, physical findings, blood counts, and serum biomarkers to create three regression models: model 1 (symptoms and signs), model 2 (model 1 plus sonographic hepatosplenomegaly and blood counts), and model 3 (model 2 plus hepatobiliary biomarkers). RESULTS: Among the 122 patients (72.6%) with EBV-IM and 46 patients (27.4%) with CMV-IM, the median age was 25 years and 82 patients (48.8%) were male. The median age was 10 years older in the CMV-IM group (p < 0.001) and the median interval from onset to visit was 5 days longer in the CMV-IM group (p < 0.001). Logistic regression revealed that EBV-IM was predicted by younger age, short onset-to-visit interval, lymphadenopathy, tonsillar white coat, hepatosplenomegaly, atypical lymphocytosis, and elevations of lactate dehydrogenase and gamma-glutamyl transferase. All regression models had areas under the curve of >0.9. CONCLUSION: History and physical findings, especially when used with atypical lymphocytosis and sonographic hepatosplenomegaly, can help physicians differentiate EBV-IM from CMV-IM.

Metabolic Biomarkers in Nematode C. elegans During Aging.

Changes in energy metabolism occur not only in diseases such as cancer but also in the normal development and aging processes of various organisms. These metabolic changes result to lead to imbalances in energy metabolism related to cellular and tissue homeostasis. In the model organism C. elegans, which is used to study aging, an imbalance in age-related energy metabolism exists between mitochondrial oxidative phosphorylation and aerobic glycolysis. Cellular lactate and pyruvate are key intermediates in intracellular energy metabolic pathways and can indicate age-related imbalances in energy metabolism. Thus, the cellular lactate/pyruvate ratio can be monitored as a biomarker during aging. Moreover, recent studies have proposed a candidate novel biomarker for aging and age-related declines in the nematode C. elegans.

Alteration of Breath Hydrogen and Methane in Ethanol-Fed Rats.

Chronic alcohol consumption can cause dysbiosis, but it is difficult to determine the effect of alcohol on the structure and activity of gastrointestinal tract microbiota. We therefore designed a noninvasive hydrogen breath test (HBT) to investigate the alteration in the chemical profile of gut microbiota in ethanol-fed rats. Thirteen F344/DuCri rats were fed on a commercial mash food with 16% ethanol solution drinking fluid from 4 weeks of age. HBTs were carried out on six 8-week-old and seven 24-week-old ethanol-fed rats. As controls, HBTs were carried out on sixteen 8-week-old, six 24-week-old, and five 48-week-old male rats. Six 24-week- old male rats were examined twice at 1-week intervals. HBTs were performed after fasting for 24 hr. Rats were orally administrated 4 mL/kg of 65% lactulose solution and housed in an animal chamber. The expired air was collected in a breath-sampling bag at 10-min intervals for 180 min. The hydrogen (H2) and methane (CH4) levels in the breath sample were measured using a breath analyzer and were expressed.as parts- per million (ppm). Elevated H2 and CH4 levels were more frequent in male rats. Maximal values of H2 and CH4 were highest in 8-week- old rats, followed by 48-week-old and 24-week-old rats. No ethanol-fed rat exhaled more than 2 ppm of H2 or CH4 until 180 min after the oral administration of lactulose, unlike the controls. This alteration was more obvious than that of aging or gender differentiation. We conclude that there is a close association between chronic ethanol consumption and H2 and CH4 production. An asymptomatic heavy drinker might have dysbiosis that involves gut microbiota with lower fermentation performance.

Model animals for the study of oxidative stress from complex II.

Mitochondria play a role of energy production and produce intracellular reactive oxygen species (ROS), especially superoxide anion (O2(-)) as a byproduct of energy metabolism at the same time. O2(-) is converted from oxygen and is overproduced by excessive electron leakage from the mitochondrial respiratory chain. It is well known that mitochondrial complexes I and III in the electron transport system are the major endogenous ROS sources. We have previously demonstrated that mutations in complex II can result in excessive ROS (specifically in SDHC: G71E in Caenorhabditis elegans, I71E in Drosophila and V69E in mouse). Moreover, this results in premature death in C. elegans and Drosophila as well as tumorigenesis in mouse embryonic fibroblast cells. In humans, it has been reported that mutations in SDHB, SDHC or SDHD, which are the subunits of mitochondrial complex II, often result in inherited head and neck paragangliomas (PGLs). Recently, we established Tet-mev-1 conditional transgenic mice using our uniquely developed Tet-On/Off system, which can induce the mutated SDHC gene to be equally and competitively expressed compared to the endogenous wild-type SDHC gene. These mice experienced mitochondrial respiratory chain dysfunction that resulted in oxidative stress. The mitochondrial oxidative stress caused excessive apoptosis in several tissues leading to low-birth-weight infants and growth retardation during neonatal developmental phase in Tet-mev-1 mice. Tet-mev-1 mice also displayed precocious age-dependent corneal physiological changes, delayed corneal epithelialization, decreased corneal endothelial cells, thickened Descemet's membrane and thinning of parenchyma with corneal pathological dysfunctions such as keratitis, Fuchs' corneal dystrophy (FCD) and probably keratoconus after the normal development and growth phase. Here, we review the relationships between mitochondrial oxidative stress and phenomena in mev-1 animal models with mitochondrial complex II SDHC mutations. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.

Interrelationships between mitochondrial fusion, energy metabolism and oxidative stress during development in Caenorhabditis elegans.

Mitochondria are known to be dynamic structures with the energetically and enzymatically mediated processes of fusion and fission responsible for maintaining a constant flux. Mitochondria also play a role of reactive oxygen species production as a byproduct of energy metabolism. In the current study, interrelationships between mitochondrial fusion, energy metabolism and oxidative stress on development were explored using a fzo-1 mutant defective in the fusion process and a mev-1 mutant overproducing superoxide from mitochondrial electron transport complex II of Caenorhabditis elegans. While growth and development of both single mutants was slightly delayed relative to the wild type, the fzo-1;mev-1 double mutant experienced considerable delay. Oxygen sensitivity during larval development, superoxide production and carbonyl protein accumulation of the fzo-1 mutant were similar to wild type. fzo-1 animals had significantly lower metabolism than did N2 and mev-1. These data indicate that mitochondrial fusion can profoundly affect energy metabolism and development.

The role of mitochondrial superoxide anion (O2(-)) on physiological aging in C57BL/6J mice.

Much attention has been focused on the mitochondrial superoxide anion (O2(-)), which is also a critical free radial produced by ionizing radiation. The specific role of the mitochondrial O2(-) on physiological aging in mammals is still unclear despite wide-spread evidence that oxidative stress is involved in aging and age-related diseases. The major endogenous source of O2(-) is generated as a byproduct of energy metabolism from mitochondria. In order to better understand how O2(-)relates to metazoan aging, we have comprehensively examined age-related changes in the levels of oxidative damage, mitochondrial O2(-) production, mitochondrial antioxidant enzyme activity and apoptosis induction in key organs of an inbred mouse strain (C57BL/6J). Oxidative damage accumulated and excess apoptosis occurred in the brain, oculus and kidney with aging, but comparatively little occurred in the heart and muscle. These rates are correlated with O2(-) levels. Mitochondrial O2(-) production levels increased with aging in the brain, oculus and kidney, and did not significantly increased in the heart and muscle. In contrast to O2(-) production, mitochondrial SOD activities increased in heart and muscle, and remained unchanged in the brain, oculus and kidney with aging. These results suggest that O2(-) production has high organ specificity, and oxidative damage by O2(-) from mitochondria mediated apoptosis can lead to organ atrophy and physiological dysfunction. In addition, O2(-) from mitochondria plays a core role in physiological aging.

[Human parvovirus B19 infection in 15 adults--two-year Toho University Hospital study].

Human parvovirus B19 infection in adults features clinical symptoms and laboratory abnormal findings unlike those in children commonly associated with cheek rash. We diagnosed 15 adult cases based on the positive increase in anti-parvovirus B19 IgM antibody (8.89 +/- 7.86 mean +/- SD, enzyme immunoassay (EIA)). Antibody titer was measured in 78 patients clinically showing fever, edema, exanthema, arthralgia, and myalgia among 11,040 outpatients first visiting the hospital from January 2005 to December 2007. Based on clinical and laboratory findings for these 15 cases, we recommended that physicians taking anti-parvovirus B19 antibody blood samples note whether (1) the level of C reactive protein is negative or low and without leucocytosis; (2) a miliary rash is observed in short duration (rarely facial); (3) arthralgia and/or myalgia is present in the extremities (sometimes asymmetrical); (4) edema is present in the extremities, especially finger, ankle, or sole of the foot; (5) contact has been made with ill children; (6) flu-like symptoms occur such as fatigue, headache, or fever;and (7) normo- or hypocomplementemia and/or antinuclear antibody is positive. Patients who fulfill requirement (1) plus at least three of requirements (2) through (7) should have a blood sample taken. We retrospectively studied 78 cases using these requirements, finding their sensitivity to be 100% (15/15), specificity to be 88.9% (56/63), positive predictive value to be 68.1% (15/22) and negative predictive value to be 100% (56/56). These requirements are thus useful in selecting patients for measuring antibody titer and definitively diagnosing severe or persistent parvovirus B19 infection occationally observed in adults.

Clinical differentiation of acute appendicitis and right colonic diverticulitis: A case-control study.

BACKGROUND: Acute right colonic diverticulitis (ARCD) is an important differential diagnosis of acute appendicitis (AA) in Asian countries because of the unusually high prevalence of right colonic diverticula. Due to qualitative improvement and the high penetration rate of computed tomography (CT) scanning in Japan, differentiation of ARCD and AA mainly depends on this modality. But cost, limited availability, and concern for radiation exposure make CT scanning problematic. Differential findings of ARCD from AA are based on several small studies that used univariate comparisons from Korea and Taiwan. Previous studies on clinical and laboratory differences between AA and ARCD are limited. AIM: To determine clinical differences between AA and ARCD for differentiation of these two diagnoses by creating a logistic regression model. METHODS: We performed an exploratory single-center retrospective case-control study evaluating 369 Japanese patients (age ≥ 16 years), 236 (64.0%) with AA and 133 (36.0%) with ARCD, who were hospitalized between 2012 and 2016. Diagnoses were confirmed by CT images. We compared age, sex, onset-to-visit interval, epigastric/periumbilical pain, right lower quadrant (RLQ) pain, nausea/vomiting, diarrhea, anorexia, medical history, body temperature, blood pressure, heart rate, RLQ tenderness, peritoneal signs, leukocyte count, and levels of serum creatinine, serum C-reactive protein (CRP), and serum alanine aminotrans-ferase. We subsequently performed logistic regression analysis for differentiating AA from ARCD based on the results of the univariate analyses. RESULTS: In the AA and ARCD groups, median ages were 35.5 and 41.0 years, respectively (p=0.011); median onset-to-visit intervals were 1 [interquartile range (IQR): 0-1] and 2 (IQR: 1-3) days, respectively (P < 0.001); median leukocyte counts were 12600 and 11500/mm3, respectively (P = 0.002); and median CRP levels were 1.1 (IQR: 0.2-4.1) and 4.9 (IQR: 2.9-8.5) mg/dL, respectively (P < 0.001). In the logistic regression model, odds ratios (ORs) were significantly high in nausea/vomiting (OR: 3.89, 95%CI: 2.04-7.42) and anorexia (OR: 2.13, 95%CI: 1.06-4.28). ORs were significantly lower with a longer onset-to-visit interval (OR: 0.84, 95%CI: 0.72-0.97), RLQ pain (OR: 0.28, 95%CI: 0.11-0.71), history of diverticulitis (OR: 0.034, 95%CI: 0.005-0.20), and CRP level > 3.0 mg/dL (OR: 0.25, 95%CI: 0.14-0.43). The regression model showed good calibration, discrimination, and optimism. CONCLUSION: Clinical findings can differentiate AA and ARCD before imaging studies; nausea/vomiting and anorexia suggest AA, and longer onset-to-visit interval, RLQ pain, previous diverticulitis, and CRP level > 3.0 mg/dL suggest ARCD.

Extensive atrophic gastritis linked to increased levels of intraluminal hydrogen gas.

BACKGROUND/AIMS: Gastric acid plays an important part in the prevention of bacterial colonization of the gastrointestinal tract. If these bacteria have an ability of hydrogen (H2) fermentation, intraluminal H2 gas might be detected. We attempted to measure the intraluminal H2 concentrations to determine the bacterial overgrowth in the gastrointestinal tract. METHODOLOGY: Studies were performed in 647 consecutive patients undergoing upper endoscopy. At the time of endoscopic examination, we intubated the stomach and the descending part of the duodenum without inflation by air, and 20 ml of intraluminal gas samples of both sites was collected through the biopsy channel. Intraluminal H2 concentrations were measured by gas chromatography. RESULTS: Over all, intragastric and intraduodenal H2 gas was detected in 566 (87.5%) and 524 (81.0%), respectively. The mean values of intragastric and intraduodenal H2 gas were 8.5 +/- 15.9 and 13.2 +/- 58.0 ppm, respectively. The intraduodenal H2 level was increased with the progression of atrophic gastritis, whereas the intragastric H2 level was the highest in patients without atrophic gastritis. CONCLUSIONS: The intraduodenal hydrogen levels were increased with the progression of atrophic gastritis. It is likely that the influence of hypochlorhydria on bacterial overgrowth in the proximal small intestine is more pronounced, compared to that in the stomach.

The role of the electron transport SDHC gene on lifespan and cancer.

Much attention has been focused on the hypothesis that oxidative damage plays in cellular and organismal aging. It is known that oxygen is initially converted to superoxide anion (O2-), one of reactive oxygen species (ROS), by electron leaked from mainly complex III in the electron transport system present in mitochondria, where it is the major endogenous source of ROS. We have shown that a mutation in a subunit, cytochrome b large subunit (SDHC), of complex II, also results in increasing O2- production and therefore lead to apoptosis and precocious aging in Caenorhabditis elegans. Recently, individuals with an inherited propensity for vascularized head and neck tumors (i.e., paragangliomas) have been demonstrated to contain one of several mutations in complex II. To further explore the role of oxidative stress from mitochondria on apoptosis and cancer, we established a transgenic cell line with a point mutation at the ubiquinone binding region in the SDHC gene. As expected, this mutation increased O2- production from complex II and led to excess apoptosis. Moreover, a significant fraction of the surviving cells from the apoptosis were transformed, as evidenced by increased tumor formation after injection into mice. Oxidative stress results in the damage to the cellular components including mitochondria and, therefore leads to apoptosis. Furthermore, oxidative stress must cause mutations in DNA and leads to cancer. It is suggested that oxidative stress from mitochondria play an important role of both apoptosis, which leads to precocious aging, and cancer.

A mutation in the SDHC gene of complex II increases oxidative stress, resulting in apoptosis and tumorigenesis.

Intracellular oxidative stress from mitochondria is thought to be important in carcinogenesis and tumorigenesis, but direct experimental proof is limited. In this study, a transgenic mouse cell line (SDHC E69) with a mutated SDHC gene (a subunit of complex II in the electron transport chain) was constructed to test this question. The SDHC E69 cells overproduced superoxide anion (O(2)(-)) from mitochondria, had elevated cytoplasmic carbonyl proteins and 8-OH-deoxyguanine in their DNA as well as significantly higher mutation frequencies than wild type. There were many apoptotic cells in this cell line, as predicted by the observed increase in caspase 3 activity, decrease in mitochondrial membrane potential, and structural changes in their mitochondria. In addition, some cells that escaped from apoptosis underwent transformation, as evidenced by the fact that SDHC E69 cells caused benign tumors when injected under the epithelium of nude mice. These results underscore the notion that mitochondrially generated oxidative stress can contribute to nuclear DNA damage, mutagenesis, and ultimately, tumorigenesis.

Endogenous reactive oxygen species cause astrocyte defects and neuronal dysfunctions in the hippocampus: a new model for aging brain.

The etiology of astrocyte dysfunction is not well understood even though neuronal defects have been extensively studied in a variety of neuronal degenerative diseases. Astrocyte defects could be triggered by the oxidative stress that occurs during physiological aging. Here, we provide evidence that intracellular or mitochondrial reactive oxygen species (ROS) at physiological levels can cause hippocampal (neuronal) dysfunctions. Specifically, we demonstrate that astrocyte defects occur in the hippocampal area of middle-aged Tet-mev-1 mice with the SDHCV69E mutation. These mice are characterized by chronic oxidative stress. Even though both young adult and middle-aged Tet-mev-1 mice overproduced MitoSOX Red-detectable mitochondrial ROS compared to age-matched wild-type C57BL/6J mice, only young adult Tet-mev-1 mice upregulated manganese and copper/zinc superoxide dismutase (Mn- and Cu/Zn-SODs) activities to eliminate the MitoSOX Red-detectable mitochondrial ROS. In contrast, middle-aged Tet-mev-1 mice accumulated both MitoSOX Red-detectable mitochondrial ROS and CM-H2 DCFDA-detectable intracellular ROS. These ROS levels appeared to be in the physiological range as shown by normal thiol and glutathione disulfide/glutathione concentrations in both young adult and middle-aged Tet-mev-1 mice relative to age-matched wild-type C57BL/6J mice. Furthermore, only middle-aged Tet-mev-1 mice showed JNK/SAPK activation and Ca2+ overload, particularly in astrocytes. This led to decreasing levels of glial fibrillary acidic protein and S100ß in the hippocampal area. Significantly, there were no pathological features such as apoptosis, amyloidosis, and lactic acidosis in neurons and astrocytes. Our findings suggest that the age-dependent physiologically relevant chronic oxidative stress caused astrocyte defects in mice with impaired mitochondrial electron transport chain functionality.

Age-related changes of mitochondrial structure and function in Caenorhabditis elegans.

A number of observations have been made to examine the role that mitochrondrial energetics and superoxide anion production play in the aging of wild-type Caenorhabditis elegans. Ultrastructural analyses reveal the presence of swollen mitochondria, presumably produced by fusion events. Two key mitochondrial functions - the activity of two electron transport chain complexes and oxygen consumption - decreased as animals aged. Carbonylated proteins, one byproduct of oxidative stress, accumulated in mitochondria much more than in the cytoplasm. This is consistent with the notion that mitochondria are the primary source of endogenous reactive oxygen species. However, the level of mitochondrially generated superoxide anion did not change significantly during aging, suggesting that the accumulation of oxidative damage is not due to excessive production of superoxide anion in geriatric animals. In concert, these data support the notion that the mitochondrial function is an important aging determinant in wild-type C. elegans.

The role of the electron transport gene SDHC on lifespan and cancer.

Much attention has been focused on the hypothesis that oxidative damage contributes to cellular and organismal aging. A mev-1 mutation in the cytochrome b large subunit (SDHC) of complex II results in superoxide anion (O(2)(-)) overproduction and therefore leads to apoptosis and precocious aging in the nematode Caenorhabditis elegans. To extend these data, a transgenic mouse cell line was constructed with a homologous mutation to mev-1. Many of the mutant nematode phenotypes (e.g., increased superoxide anion production, apoptosis) were recapitulated in the mouse. In addition, a significant fraction of the cells that survived apoptosis were transformed. These data support the notion that oxidative stress from mitochondria play an important role of both apoptosis, which leads to precocious aging, and cancer.

Infertility and recurrent miscarriage with complex II deficiency-dependent mitochondrial oxidative stress in animal models.

Oxidative stress is associated with some forms of both male and female infertility. However, there is insufficient knowledge of the influence of oxidative stress on the maintenance of a viable pregnancy, including pregnancy complications and fetal development. There are a number of animal models for understanding age-dependent decrease of reproductive ability and diabetic embryopathy, especially abnormal spermatogenesis, oogenesis and embryogenesis with mitochondrial dysfunctions. Several important processes occur in mitochondria, including ATP synthesis, calcium ion storage, induction of apoptosis and production of reactive oxygen species (ROS). These events have different effects on the several aspects of reproductive function. Tet-mev-1 conditional transgenic mice, developed after studies with the mev-1 mutant of the nematode C. elegans, offer the ability to carefully regulate expression of doxycycline-induced mutated SDHC(V69E) levels and hence modulate endogenous oxidative stress. The mev-1 models have served to illuminate the effects of complex II deficiency-dependent mitochondrial ROS production, although interestingly they maintain normal mitochondrial and intracellular ATP levels. In this review, the reproductive dysfunctions are presented focusing on fertility potentials in each gamete, early embryogenesis, maternal conditions with placental function and neonatal development.