Jiangang Long

A cigarette component acrolein induces accelerated senescence in human diploid fibroblast IMR-90 cells

Cigarette smoking causes various diseases, including lung cancer and cardiovascular disease, and reduces life span, though the mechanisms are not well understood. We hypothesize that smoking may cause cellular mitochondrial dysfunction and oxidative stress, leading to aging acceleration. In the present study, we tested the effects of acrolein, a major representative smoking toxicant, on human lung fibroblast IMR-90 cells with regard to cellular senescence, oxidative stress, and mitochondrial function. The results showed that subacute treatment with low dose of acrolein induces the following events compared to the control cells: cell senescence demonstrated by increases in the activity of β-galactosidase, the higher expression of p53 and p21, decreases in DNA synthesis, Sirt1 expression, and telomere length; oxidative stress occurred as the increases in the production of reactive oxygen species, DNA damage, and protein oxidation; and mitochondrial dysfunction shown as decreases in the mitochondrial membrane potential, mitochondrial biogenesis regulator PGC-1 alpha and mitochondria complex I, II, III, and V. These results suggest that acrolein may accelerate aging through the mechanism of increasing oxidative stress and mitochondrial dysfunction.

Mitochondrial Decay in the Brains of Old Rats: Ameliorating Effect of Alpha-Lipoic Acid and Acetyl-l-carnitine

To investigate the mitochondrial decay and oxidative damage resulting from aging, the activities/kinetics of the mitochondrial complexes were examined in the brains of young and old rats as well as in old rats fed R-α-lipoic acid plus acetyl-l-carnitine (LA/ALC). The brain mitochondria of old rats, compared with young rats, had significantly decreased endogenous antioxidants and superoxide dismutase activity; more oxidative damage to lipids and proteins; and decreased activities of complex I, IV and V. Complex I showed a decrease in binding affinity (increase in Km) for substrates. Feeding LA/ALC to old rats partially restored age-associated mitochondrial dysfunction to the levels of the young rats. These results indicate that oxidative mitochondrial decay plays an important role in brain aging and that a combination of nutrients targeting mitochondria, such as LA/ALC, could ameliorate mitochondrial decay through preventing mitochondrial oxidative damage.

Hydroxytyrosol protects retinal pigment epithelial cells from acrolein-induced oxidative stress and mitochondrial dysfunction

Hydroxytyrosol (HTS) is a natural polyphenol abundant in olive oil. Increasing evidence indicates HTS has beneficial effect on human health for preventing various diseases. In the present study, we investigated the protective effects of HTS on acrolein‐induced toxicity in human retinal pigment epithelial cell line, ARPE‐19, a cellular model of smoking‐ and age‐related macular degeneration. Acrolein, a major component of the gas phase cigarette smoke and also a product of lipid peroxidation in vivo, at 75 μmol/L for 24 h caused significant loss of cell viability, oxidative damage (increase in oxidant generation and oxidative damage to proteins and DNA, decrease in antioxidants and antioxidant enzymes, and also inactivation of the Keap1/Nrf2 pathway), and mitochondrial dysfunction (decrease in membrane potential, activities of mitochondrial complexes, viable mitochondria, oxygen consumption, and factors for mitochondrial biogenesis, and increase in calcium). Pre‐treatment with HTS dose dependently and also time dependently protected the ARPE‐19 cells from acrolein‐induced oxidative damage and mitochondrial dysfunction. A short‐term pre‐treatment with HTS (48 h) required > 75 μmol/L for showing protection while a long‐term pre‐treatment (7 days) showed protective effect from 5 μmol/L on. The protective effect of HTS in this model was as potent as that of established mitochondria‐targeting antioxidant nutrients. These results suggest that HTS is also a mitochondrial‐targeting antioxidant nutrient and that dietary administration of HTS may be an effective measure in reducing and or preventing cigarette smoke‐induced or age‐related retinal pigment epithelial degeneration, such as age‐associated macular degeneration.

Enhanced autophagy plays a cardinal role in mitochondrial dysfunction in type 2 diabetic Goto–Kakizaki (GK) rats: ameliorating effects of (−)-epigallocatechin-3-gallate

Oxidative stress and mitochondrial dysfunction are known to play important roles in type 2 diabetes mellitus (T2DM) and insulin resistance. However, the pathology of T2DM remains complicated; in particular, the mechanisms of mitochondrial dysfunction in skeletal muscle and other insulin-sensitive tissues are as yet unclear. In the present study, we investigated the underlying mechanisms of oxidative stress and mitochondrial dysfunction by focusing on mitochondrial dynamics, including mitochondrial biogenesis and autophagy, in skeletal muscle of a nonobese diabetic animal model--the Goto-Kakizaki (GK) rat. The results showed that GK rats exhibited impaired glucose metabolism, increased oxidative stress and decreased mitochondrial function. These dysfunctions were found to be associated with induction of LC3B, Beclin1 and DRP1 (key molecules mediating the autophagy pathway), while they appeared not to affect the mitochondrial biogenesis pathway. In addition, (-)-epigallocatechin-3-gallate (EGCG) was tested as a potential autophagy-targeting nutrient, and we found that EGCG treatment improved glucose tolerance and glucose homeostasis in GK rats, and reduced oxidative stress and mitochondrial dysfunction in skeletal muscle. Amelioration of excessive muscle autophagy in GK rats through the down-regulation of the ROS-ERK/JNK-p53 pathway leads to improvement of glucose metabolism, reduction of oxidative stress and inhibition of mitochondrial loss and dysfunction. These results suggest (a) that hyperglycemia-associated oxidative stress may induce autophagy through up-regulation of the ROS-ERK/JNK-p53 pathway, which may contribute to mitochondrial loss in soleus muscle of diabetic GK rats, and (b) that EGCG may be a potential autophagy regulator useful in treatment of insulin resistance.

Hydroxytyrosol prevents diet-induced metabolic syndrome and attenuates mitochondrial abnormalities in obese mice.

A Mediterranean diet rich in olive oil has profound influence on health outcomes including metabolic syndrome. However, the active compound and detailed mechanisms still remain unclear. Hydroxytyrosol (HT), a major polyphenolic compound in virgin olive oil, has received increased attention for its antioxidative activity and regulation of mitochondrial function. Here, we investigated whether HT is the active compound in olive oil exerting a protective effect against metabolic syndrome. In this study, we show that HT could prevent high-fat-diet (HFD)-induced obesity, hyperglycemia, hyperlipidemia, and insulin resistance in C57BL/6J mice after 17 weeks supplementation. Within liver and skeletal muscle tissues, HT could decrease HFD-induced lipid deposits through inhibition of the SREBP-1c/FAS pathway, ameliorate HFD-induced oxidative stress by enhancing antioxidant enzyme activities, normalize expression of mitochondrial complex subunits and mitochondrial fission marker Drp1, and eventually inhibit apoptosis activation. Moreover, in muscle tissue, the levels of mitochondrial carbonyl protein were decreased and mitochondrial complex activities were significantly improved by HT supplementation. In db/db mice, HT significantly decreased fasting glucose, similar to metformin. Notably, HT decreased serum lipid, at which metformin failed. Also, HT was more effective at decreasing the oxidation levels of lipids and proteins in both liver and muscle tissue. Similar to the results in the HFD model, HT decreased muscle mitochondrial carbonyl protein levels and improved mitochondrial complex activities in db/db mice. Our study links the olive oil component HT to diabetes and metabolic disease through changes that are not limited to decreases in oxidative stress, suggesting a potential pharmaceutical or clinical use of HT in metabolic syndrome treatment.

Mitochondrial nutrients improve immune dysfunction in the type 2 diabetic Goto-Kakizaki rats.

The development of type 2 diabetes is accompanied by decreased immune function and the mechanisms are unclear. We hypothesize that oxidative damage and mitochondrial dysfunction may play an important role in the immune dysfunction in diabetes. In the present study, we investigated this hypothesis in diabetic Goto‐Kakizaki rats by treatment with a combination of four mitochondrial‐targeting nutrients, namely, R‐α‐lipoic acid, acetyl‐L‐carnitine, nicotinamide and biotin. We first studied the effects of the combination of these four nutrients on immune function by examining cell proliferation in immune organs (spleen and thymus) and immunomodulating factors in the plasma. We then examined, in the plasma and thymus, oxidative damage biomarkers, including lipid peroxidation, protein oxidation, reactive oxygen species, calcium and antioxidant defence systems, mitochondrial potential and apoptosis‐inducing factors (caspase 3, p53 and p21). We found that immune dysfunction in these animals is associated with increased oxidative damage and mitochondrial dysfunction and that the nutrient treatment effectively elevated immune function, decreased oxidative damage, enhanced mitochondrial function and inhibited the elevation of apoptosis factors. These effects are comparable to, or greater than, those of the anti‐diabetic drug pioglitazone. These data suggest that a rational combination of mitochondrial‐targeting nutrients may be effective in improving immune function in type 2 diabetes through enhancement of mitochondrial function, decreased oxidative damage, and delayed cell death in the immune organs and blood.

D-galactose toxicity in mice is associated with mitochondrial dysfunction: protecting effects of mitochondrial nutrient R-alpha-lipoic acid.

Abstractd-Galactose (d-gal) -induced aging models in Drosophila, houseflies, mice and rats have been widely used; however, the underlying mechanisms are poorly understood. To investigate the involvement of mitochondrial dysfunction of d-gal, mitochondrial function was examined in the brain and liver of C57BL/6J mice, subjected to a treatment of d-gal with or without a concomitant treatment with a mitochondrial nutrient, R-alpha-lipoic acid (LA). d-Gal treatment induced a significant decrease in succinate-linked respiratory control ratio (RCR) and ADP/O ratio in the liver and brain, and also a significant increase in the maximum velocity (Vmax) and substrate binding affinity (Km) of complex II in the liver. LA treatment to d-gal-injected animals restored mitochondrial RCR in both brain and liver, ADP/O and Km of complex II in the liver. These results suggest LA is effective in delaying d-gal toxicity by ameliorating mitochondrial dysfunction.

Mitochondrial Dysfunction in Obesity-Associated Nonalcoholic Fatty Liver Disease: The Protective Effects of Pomegranate with Its Active Component Punicalagin

AIMS Punicalagin (PU) is one of the major ellagitannins found in the pomegranate (Punica granatum), which is a popular fruit with several health benefits. So far, no studies have evaluated the effects of PU on nonalcoholic fatty liver disease (NAFLD). Our work aims at studying the effect of PU-enriched pomegranate extract (PE) on high fat diet (HFD)-induced NAFLD. RESULTS PE administration at a dosage of 150 mg/kg/day significantly inhibited HFD-induced hyperlipidemia and hepatic lipid deposition. As major contributors to NAFLD, increased expression of pro-inflammatory cytokines such as tumor necrosis factor-alpha, interleukins 1, 4, and 6 as well as augmented oxidative stress in hepatocytes followed by nuclear factor (erythroid-derived-2)-like 2 (Nrf2) activation were normalized through PE supplementation. In addition, PE treatment reduced uncoupling protein 2 (UCP2) expression, restored ATP content, suppressed mitochondrial protein oxidation, and improved mitochondrial complex activity in the liver. In contrast, mitochondrial content was not affected despite increased peroxisomal proliferator-activated receptor-gamma coactivator-1α (PGC-1α) and elevated expression of genes related to mitochondrial beta-oxidation after PE treatment. Finally, PU was identified as the predominant active component of PE with regard to the lowering of triglyceride and cholesterol content in HepG2 cells, and both PU- and PE-protected cells from palmitate induced mitochondrial dysfunction and insulin resistance. INNOVATION Our work presents the beneficial effects of PE on obesity-associated NAFLD and multiple risk factors. PU was proposed to be the major active component. CONCLUSIONS By promoting mitochondrial function, eliminating oxidative stress and inflammation, PU may be a useful nutrient for the treatment of NAFLD.

An improved spectrophotometric method for a more specific and accurate assay of mitochondrial complex III activity.

BACKGROUND The determination of the activity of complex III in tissue samples provides critical evidence in the diagnosis of mitochondrial disorders and diseases associated with mitochondrial dysfunction. However, great variations have been seen in the literature due to the use of different assays. METHODS Reaction conditions of an improved spectrophotometric method exhibiting higher specificity for complex III activity than the methods currently used, were studied. RESULTS Optimum conditions, using bovine serum albumin at 0.01% and Tween-20 at 0.05%, were defined. The present method possesses more antimycin A-sensitive complex III activity, compared to previous methods. Thus, this improved method is sensitive and suitable for assaying complex III in both crude tissue homogenate and isolated mitochondria of liver, heart, skeletal muscle and brain. CONCLUSIONS This spectrophotometric assay is sensitive, and specific for complex III activity because of the negligible blank rate and high antimycin A-sensitive activity. The low concentration of bovine serum albumin, and the use of inexpensive detergent Tween-20 make this improved method more robust for its use in a clinical laboratory setting.

Compromised mitochondrial remodeling in compensatory hypertrophied myocardium of spontaneously hypertensive rat

BACKGROUND Hypertension leads to cardiac hypertrophy as an adaptive response to increased workload. While initial development of hypertrophy is compensatory when contractile function is maintained, persistent stress on heart leads to deteriorated cardiac function and onset of heart failure. Mitochondrial dysfunction develops in the failing heart; however, whether it presents in compensatory cardiac hypertrophy is controversial. METHODS Spontaneously hypertensive rats (SHRs) and age-matched normotensive Wistar Kyoto rats were used in the study. Mitochondrial function and remodeling-related mechanisms in the left ventricles were measured by enzyme activity tests, Western blots, and reverse transcriptase polymerase chain reaction. RESULTS Compensatory cardiac hypertrophy in SHR was indicated by higher heart/weigh ratio, left ventricular systolic pressure and ±dp/dt(max) (P<.001, P<.05, and P<.01, respectively). Enzyme activities of mitochondrial complex I and II were significantly reduced (P<.05 and P<.01) in SHR in concert with decreased expression of complex subunits (P<.01 for NDUFS3, P=.068 for SDHB, and P<.05 for ATP5A1). Mitochondrial fission protein Drp1 was decreased (P<.05), while fusion protein OPA1 was increased (P<.01). Parkin and SirT1/AMPK-PGC-1α signaling, responsible for mitochondrial elimination and biogenesis respectively, were decreased in SHR (P<.01 for Parkin, P<.001 for SirT1 and p-AMPK). CONCLUSION Our results implicated that mitochondrial function and remodeling, indicated by mitochondrial enzyme activities and remodeling-related molecules, were compromised in compensatory hypertrophied myocardium of the SHR hypertensive model. SUMMARY Mitochondrial function in compensatory hypertrophied myocardium is controversial. Our present study found mitochondrial dysfunction in the left ventricle of spontaneously hypertensive rats, which was possibly a result of compromised mitochondrial remodeling including mitochondrial dynamics, elimination, and biogenesis.