Exercise couples mitochondrial function with skeletal muscle fiber type via ROS-mediated epigenetic modification

Skeletal muscle is a heterogeneous tissue composed of different types of muscle fibers, demonstrating substantial plasticity. Physiological or pathological stimuli can induce transitions in muscle fiber types. However, the precise regulatory mechanisms behind these transitions remains unclear. This paper reviews the classification and characteristics of muscle fibers, along with the classical mechanisms of muscle fiber type transitions. Additionally, the role of exercise-induced muscle fiber type transitions in disease intervention is reviewed. Epigenetic pathways mediate cellular adaptations and thus represent potential targets for regulating muscle fiber type transitions. This paper focuses on the mechanisms by which epigenetic modifications couple mitochondrial function and contraction characteristics. Reactive Oxygen Species (ROS) are critical signaling regulators for the health-promoting effects of exercise. Finally, we discuss the role of exercise-induced ROS in regulating epigenetic modifications and the transition of muscle fiber types.

ABHD2 deficiency aggravates ovalbumin-induced airway remodeling through the PI3K/Akt pathway in an animal model of chronic asthma

Airway remodeling is a major pathological characteristic of chronic obstructive pulmonary disease (COPD). This study aimed to investigate the effect of Abhd2 deficiency on ovalbumin (OVA)-induced airway remodeling and inflammation in vivo. Abhd2-deficient mice were used to establish an OVA-induced asthma model. Lung tissues were analyzed using hematoxylin and eosin (HE) staining, Masson staining, immunohistochemistry, quantitative reverse transcription- polymerase chain reaction (qRT-PCR), and western blotting were used to determine the role of Abhd2 in the regulation of OVA-induced airway remodeling and inflammation. Our findings revealed that the RNA expression of inflammatory factors, including IL-1β, IL-6, IL-4, and IL-13, was significantly increased in OVA-induced Abhd2 Gt/Gt asthmatic mice. The expression of IFN-γ was decreased significantly in OVA-induced Abhd2 Gt/Gt asthmatic mice. The protein expression of airway remodeling factors, including α-SMA, type I collagen, and Ki67, was also increased in OVA-induced Abhd2 Gt/Gt asthmatic mice compared to that in OVA-induced wild-type (WT) mice. Additionally, Abhd2 deficiency promoted the expression of p-Akt in tissues of the asthma model. These results suggest that Abhd2 deficiency exacerbates airway remodeling and inflammation through the PI3K/Akt pathway in chronic asthma.

Exercise Improves the Coordination of the Mitochondrial Unfolded Protein Response and Mitophagy in Aging Skeletal Muscle

The mitochondrial unfolded protein response (UPRmt) and mitophagy are two mitochondrial quality control (MQC) systems that work at the molecular and organelle levels, respectively, to maintain mitochondrial homeostasis. Under stress conditions, these two processes are simultaneously activated and compensate for each other when one process is insufficient, indicating mechanistic coordination between the UPRmt and mitophagy that is likely controlled by common upstream signals. This review focuses on the molecular signals regulating this coordination and presents evidence showing that this coordination mechanism is impaired during aging and promoted by exercise. Furthermore, the bidirectional regulation of reactive oxygen species (ROS) and AMPK in modulating this mechanism is discussed. The hierarchical surveillance network of MQC can be targeted by exercise-derived ROS to attenuate aging, which offers a molecular basis for potential therapeutic interventions for sarcopenia.

Resveratrol glycoside mediates microglial endoplasmic reticulum stress to mitigate LPS-induced sepsis-associated cognitive dysfunction

BACKGROUND

As a common complication of sepsis, sepsis-associated encephalopathy (SAE) is characterized by diffuse brain dysfunction and neurological damage and closely associated with long-term cognitive dysfunction. The dysregulated host response triggered by neurotoxicity of microglia is an important cause of diffuse brain dysfunction in SAE. Resveratrol glycoside has anti-inflammatory and antioxidant effects. However, there is no evidence whether resveratrol glycoside could alleviate SAE.

METHODS

LPS administration was used to induce SAE in mice. Step-down test (SDT) and Morris water maze test (MWM) were performed to evaluate the cognitive function of mice with SAE. Western blot and immunofluorescence were used to reveal the endoplasmic reticulum stress (ERS) regulation. Microglia cell line BV-2 was used to validate the effect of resveratrol glycoside on LPS-stimulated ERS in vitro.

RESULTS

Compared with the control group, LPS-stimulated mice had decreased cognitive function, but this phenomenon was well reversed by resveratrol glycoside administration, in which the SDT assay showed longer retention time, both in short-term memory (STM) and long-term memory (LTM). Western blot indicated that the expression of ER stress-related protein PERK/CHOP in LPS-stimulated mice were significantly increased, while that in the resveratrol glycoside-treated group were relieved. Furthermore, Immunofluorescence revealed resveratrol glycoside mainly worked on microglia in mediating the ER stress, in which the expression of PERK/CHOP were significantly inhibited in resveratrol glycoside group mice. In vitro, BV2 showed consistent results with the aforementioned.

CONCLUSION

Resveratrol glycoside could alleviate the cognitive dysfunction caused by LPS-induced SAE, mainly by inhibiting the ER stress and maintaining the homeostasis of ER function of microglia.

The specific mitochondrial unfolded protein response in fast- and slow-twitch muscles of high-fat diet-induced insulin-resistant rats

INTRODUCTION

Skeletal muscle insulin resistance (IR) plays an important role in the pathogenesis of type 2 diabetes mellitus. Skeletal muscle is a heterogeneous tissue composed of different muscle fiber types that contribute distinctly to IR development. Glucose transport shows more protection in slow-twitch muscles than in fast-twitch muscles during IR development, while the mechanisms involved remain unclear. Therefore, we investigated the role of the mitochondrial unfolded protein response (UPRmt) in the distinct resistance of two types of muscle in IR.

METHODS

Male Wistar rats were divided into high-fat diet (HFD) feeding and control groups. We measured glucose transport, mitochondrial respiration, UPRmt and histone methylation modification of UPRmt-related proteins to examine the UPRmt in the slow fiber-enriched soleus (Sol) and fast fiber-enriched tibialis anterior (TA) under HFD conditions.

RESULTS

Our results indicate that 18 weeks of HFD can cause systemic IR, while the disturbance of Glut4-dependent glucose transport only occurred in fast-twitch muscle. The expression levels of UPRmt markers, including ATF5, HSP60 and ClpP, and the UPRmt-related mitokine MOTS-c were significantly higher in slow-twitch muscle than in fast-twitch muscle under HFD conditions. Mitochondrial respiratory function is maintained only in slow-twitch muscle. Additionally, in the Sol, histone methylation at the ATF5 promoter region was significantly higher than that in the TA after HFD feeding.

CONCLUSION

The expression of proteins involved in glucose transport in slow-twitch muscle remains almost unaltered after HFD intervention, whereas a significant decline of these proteins was observed in fast-twitch muscle. Specific activation of the UPRmt in slow-twitch muscle, accompanied by higher mitochondrial respiratory function and MOTS-c expression, may contribute to the higher resistance to HFD in slow-twitch muscle. Notably, the different histone modifications of UPRmt regulators may underlie the specific activation of the UPRmt in different muscle types. However, future work applying genetic or pharmacological approaches should further uncover the relationship between the UPRmt and insulin resistance.

[Distribution and gene characteristics of H3, H4 and H6 subtypes of low pathogenic avian influenza viruses in environment related avian influenza viruses during 2014-2021 in China]

Objective: To analyze the characteristics of low pathogenic H3, H4 and H6 subtypes of avian influenza viruses in environment related avian influenza viruses in China from 2014 to 2021. Methods: Surveillance sites were located in 31 provinces, autonomous region and municipalities to collect environmental samples related to avian influenza, detect the nucleic acid detection of influenza A virus, isolate virus, deeply sequence, analyze pathogenicity related molecular sites, and determine the distribution and variation characteristics of common H3, H4 and H6 subtypes of avian influenza virus in different regions, places and sample types. Results: A total of 388 645 samples were collected. The positive rate of low pathogenic H3 (0.56‰) and H6 (0.53‰) was higher than that of H4 (0.09‰). The positive rate of H4 subtype virus in live poultry market was higher than that in other places, and the difference was statistically significant. The positive rate of H3 and H6 subtypes in sewage samples was higher than that in other samples, and the difference was statistically significant. The positive rate of H3, H4 and H6 viruses in the south was higher than that in the north, and the difference was statistically significant. December was the most active time for virus. The analysis of pathogenicity related molecular sites showed that H3, H4 and H6 subtypes of viruses combined with avian influenza virus receptors, and some gene sites related to increased pathogenicity had mutations. Conclusion: The H3, H4 and H6 subtypes of low pathogenic avian influenza viruses have a high isolation positive rate in the live poultry market and sewage. The distribution of the three subtypes of viruses has obvious regional and seasonal characteristics, and the genetic characteristics still show the feature of low pathogenic avian influenza.

Impact of Exercise and Aging on Mitochondrial Homeostasis in Skeletal Muscle: Roles of ROS and Epigenetics

Aging causes degenerative changes such as epigenetic changes and mitochondrial dysfunction in skeletal muscle. Exercise can upregulate muscle mitochondrial homeostasis and enhance antioxidant capacity and represents an effective treatment to prevent muscle aging. Epigenetic changes such as DNA methylation, histone posttranslational modifications, and microRNA expression are involved in the regulation of exercise-induced adaptive changes in muscle mitochondria. Reactive oxygen species (ROS) play an important role in signaling molecules in exercise-induced muscle mitochondrial health benefits, and strong evidence emphasizes that exercise-induced ROS can regulate gene expression via epigenetic mechanisms. The majority of mitochondrial proteins are imported into mitochondria from the cytosol, so mitochondrial homeostasis is regulated by nuclear epigenetic mechanisms. Exercise can reverse aging-induced changes in myokine expression by modulating epigenetic mechanisms. In this review, we provide an overview of the role of exercise-generated ROS in the regulation of mitochondrial homeostasis mediated by epigenetic mechanisms. In addition, the potential epigenetic mechanisms involved in exercise-induced myokine expression are reviewed.

Mitochondrial ROS Produced by Skeletal Muscle Mitochondria Promote the Decisive Signal for UPRmt Activation

The mitochondrial unfolded protein response (UPRmt) can repair and remove misfolded or unfolded proteins in mitochondria and enhance mitochondrial protein homeostasis. Reactive oxygen species (ROS) produced by regular exercise is a crucial signal for promoting health, and skeletal muscle mitochondria are the primary source of ROS during exercise. To verify whether UPRmt is related to ROS produced by mitochondria in skeletal muscle during regular exercise, we adapted MitoTEMPO, mitochondrially targeted antioxidants, and ROS production by mitochondria. Our results showed that mitochondrial ROS is the key factor for activating UPRmt in different pathways.

Anticholinergics combined with alpha-blockers for treating lower urinary tract symptoms related to benign prostatic obstruction

BACKGROUND

Lower urinary tract symptoms (LUTS) due to benign prostatic obstruction (BPO) represent one of the most common clinical complaints in men. Alpha-blockers are widely used as first-line therapy for men with LUTS secondary to BPO, but up to one third of men report no improvement in their LUTS after taking alpha-blockers. Anticholinergics used in addition to alpha-blockers may help improve symptoms but it is uncertain how effective they are.  OBJECTIVES: To assess the effects of combination therapy with anticholinergics and alpha-blockers in men with LUTS related to BPO.

SEARCH METHODS

We performed a comprehensive search of medical literature, including the Cochrane Library, MEDLINE, Embase, and trials registries, with no restrictions on the language of publication or publication status. The date of the latest search was 7 August 2020.

SELECTION CRITERIA

We included randomized controlled trials. Inclusion criteria were men with LUTS secondary to BPO, ages 40 years or older, and a total International Prostate Symptom Score of 8 or greater. We excluded trials of men with a known neurogenic bladder due to spinal cord injury, multiple sclerosis, or central nervous system disease, and those examining medical therapy for men who were treated with surgery for BPO. We performed three comparisons: combination therapy versus placebo, combination therapy versus alpha-blockers monotherapy, and combination therapy versus anticholinergics monotherapy.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the literature, extracted data, and assessed risk of bias. We performed statistical analyses using a random-effects model and interpreted data according to the Cochrane Handbook for Systematic Reviews of Interventions. We used the GRADE approach to rate the certainty of evidence.

MAIN RESULTS

We included 23 studies with 6285 randomized men across three comparisons. The mean age of participants ranged from 54.4 years to 73.9 years (overall mean age 65.7 years). Of the included studies, 12 were conducted with a single-center setting, while 11 used a multi-center setting. We only found short-term effect (12 weeks to 12 months) of combination therapy based on available evidence. Combination therapy versus placebo: based on five studies with 2369 randomized participants, combination therapy may result in little or no difference in urologic symptom scores (mean difference (MD) -2.73, 95% confidence interval (CI) -5.55 to 0.08; low-certainty evidence). We are very uncertain about the effect of combination therapy on quality of life (QoL) (MD -0.97, 95% CI -2.11 to 0.16; very low-certainty evidence). Combination therapy likely increases adverse events (risk ratio (RR) 1.24, 95% CI 1.04 to 1.47; moderate-certainty evidence); based on 252 adverse events per 1000 participants in the placebo group, this corresponds to 61 more adverse events (95% CI 10 more  to 119 more) per 1000 participants treated with combination therapy. Combination therapy versus alpha-blockers alone: based on 22 studies with 4904 randomized participants, we are very uncertain about the effect of combination therapy on urologic symptom scores (MD -2.04, 95% CI -3.56 to -0.52; very low-certainty evidence) and QoL (MD -0.71, 95% CI -1.03 to -0.38; very low-certainty evidence). Combination therapy may result in little or no difference in adverse events rate (RR 1.10, 95% CI 0.90 to 1.34; low-certainty evidence); based on 228 adverse events per 1000 participants in the alpha-blocker group, this corresponds to 23 more adverse events (95% CI 23 fewer to 78 more) per 1000 participants treated with combination therapy. Combination therapy compared to anticholinergics alone: based on three studies with 1218 randomized participants, we are very uncertain about the effect of combination therapy on urologic symptom scores (MD -3.71, 95% CI -9.41 to 1.98; very low-certainty evidence). Combination therapy may result in an improvement in QoL (MD -1.49, 95% CI -1.88 to -1.11; low-certainty evidence). Combination therapy likely results in little to no difference in adverse events (RR 1.26, 95% CI 0.81 to 1.95; moderate-certainty evidence); based on 115 adverse events per 1000 participants in the anticholinergic alone group, this corresponds to 4 fewer adverse events (95% CI 7 fewer to 13 more) per 1000 participants treated with combination therapy.

AUTHORS' CONCLUSIONS

Based on the findings of the review, combination therapy with anticholinergics and alpha-blockers are associated with little or uncertain effects on urologic symptom scores compared to placebo, alpha-blockers, or anticholinergics monotherapy. However, combination therapy may result in an improvement in quality of life compared to anticholinergics monotherapy, but an uncertain effect compared to placebo, or alpha-blockers. Combination therapy likely increases adverse events compared to placebo, but not compared to alpha-blockers or anticholinergics monotherapy. The findings of this review were limited by study limitations, inconsistency, and imprecision. We were unable to conduct any of the predefined subgroup analyses.

Mouse Model to Explore the Therapeutic Effect of Nano-Doxorubicin Drug Delivery System on Bladder Cancer

To study the therapeutic effect of nano-dosin-loaded drug system in mouse bladder cancer, a luciferase-labeled mouse bladder cancer cell line and a mouse bladder cancer model were constructed. In vivo imaging monitors tumor growth and uses a combination of photothermal, immune, and chemotherapy to treat the mouse model. With doxorubicin as an antitumor drug carrier, the drug loading, in vitro drug release, cytotoxicity and behavior in cells of mesoporous nano particle-targeted drug delivery system were studied. The cells were injected into the bladder through the urethra, and the mouse bladder cancer subcutaneous model was treated with gelatin-coated single-walled carbon nanotube-encapsulated mouse granulocytes-macrophage colony-stimulating factor and doxorubicin. In the process of using, the use of near-infrared light for irradiation, thereby achieving the combined effect of photothermal, immune and chemotherapy. The experimental results show that the prepared doxorubicin prodrug delivery system can enhance the targeted therapeutic effect and reduce the toxicity and side effects of the drug. Especially for those cancer cells or tissues with overexpression of folate receptors, it has a better therapeutic effect and provides reference for the treatment of subsequent bladder cancer.

Innovative development ideas of web-based medical teaching during the COVID-19 epidemic

OBJECTIVE

In response to the sudden COVID-19 epidemic outbreak, China's Ministry of Education proposed "continuing teaching and learning regardless of suspending classes" to provide "available courses and teachers" for students. Web-based teaching has become the main teaching method of medical colleges and universities during the COVID-19 epidemic period. Before the outbreak, the concept and technology of web-based teaching had been partially implemented. The epidemic situation has promoted the implementation of large-scale web-based teaching and the multidimensional development of education in China. Furthermore, there are higher requirements for information teaching. Teachers and students cannot adapt to the web-based teaching mode. The lack of interaction is a problem in the web-based teaching. To adapt to the rapid development of information technology, medical colleges and universities must consider the COVID-19 epidemic as an opportunity to quickly update educational concepts, train teachers' Internet thinking, innovate the web-based teaching mode, and make full use of the network platform to provide better teaching and services. Moreover, medical colleges and universities should eliminate the weaknesses of web-based teaching and improve the quality and connotation of teaching.

Effects of the prebiotic inulin-type fructans on post-antibiotic reconstitution of the gut microbiome

AIMS

Interventions using prebiotic inulin-type fructans (ITFs) are widely prescribed to modulate the gut microbiota composition and activity to promote health. However, the impacts of ITFs on post-antibiotic reconstitution of the gut microbiome remain incompletely understood. The aim of the present study was to investigate the effects of ITFs supplementation on intestinal inflammation, the composition of the intestinal microbiota and the colonic transcriptome after antibiotic treatment.

METHODS AND RESULTS

Male BALB/c mice were subjected to an antibiotic cocktail (ABx) treatment for 7 days, and their microbiomes were then reconstituted either spontaneously or with ITFs supplementation (5%) for 14 days. Our data showed that ITFs supplementation delayed the recovery of antibiotic-induced colitis compared with the spontaneous recovery. Neither ITFs supplementation nor spontaneous recovery could restore the microbial community composition at the genus level back to its initial composition. ITFs supplementation increased the relative abundance of some beneficial bacteria and butyrate levels, but resulted in selective blooms of some opportunistic pathogens and elevated the pathways associated with diseases linked to gut microbiota function. Both ITFs supplementation and spontaneous recovery could restore the colonic transcriptome nearly to the initial profile to a certain extent; however, ITFs supplementation delayed the restoration of the immunoglobulin genes compared to spontaneous recovery.

CONCLUSION

These data showed that post-antibiotic ITFs consumption did not always lead to beneficial effects but might lead to potential adverse effects in the context of dysbiosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings highlighted that caution is required when supplementing ITFs to restore intestinal homeostasis in the context of dysbiosis resulting from broad-spectrum antibiotics.

[Research progress in regulation of exercise on mitochondrial respiratory chain spercomplex]

The mitochondrial respiratory chain supercomplex (mitoSC) is a complex super-assembly formed by free complexes on the mitochondrial inner membrane respiratory chain through the interaction between their subunits, mainly including mitoSCI₁+III₂+IV_1-4, mitoSCI₁+III₂, mitoSCIII₂+IV_1-2, high molecular weight mitoSC (HMW mitoSC) and mitochondrial metacomplex (mitoMC). mitoSC has been shown to improve the efficiency of electron transport in the respiratory chain and reduce the production of reactive oxygen species. The species and content of mitoSC change in different tissues in aging and many mitochondria-related diseases. By summarizing the structure and function of mitoSC in different tissues of human and mammals, and the changes of mitoSC under conditions of aging, heart disease, type 2 diabetes, cancer and genetic defects, this review focuses on the effects of exercise on mitoSC and its related regulation mechanisms in order to offer an insight for exercise interventions in mitochondria-related diseases.

Post-mortem findings in a patient with avian influenza A (H5N6) virus infection

Avian influenza A (H5N6) has been found to infect humans, and has resulted in ten cases with six deaths in China since 2014. Here, we describe the systematic post-mortem pathology of a patient fatally infected with H5N6 virus and evaluate the associated pathogenesis compared with H1N1 pdm09 fatal cases. The most prominent histopathological features were diffuse alveolar damage and pulmonary vasculitis in the lungs of the patient. The virus disseminated to extrapulmonary organs, including the brain. Compared with H1N1 pdm09 fatal infection, H5N6 infection induced a more exacerbated immune response involving overt pulmonary inflammation, which led to alveolar damage and respiratory failure.

[Exercise training in hypoxia prevents hypoxia induced mitochondrial DNA oxidative damage in skeletal muscle]

This study was undertaken to investigate the effect of exercise training on mitochondrial DNA (mtDNA) oxidative damage and 8-oxoguanine DNA glycosylase-1 (OGG1) expression in skeletal muscle of rats under continuous exposure to hypoxia. Male Sprague-Dawley rats were randomly divided into 4 groups (n = 8): normoxia control group (NC), normoxia training group (NT), hypoxia control group (HC), and hypoxia training group (HT). The hypoxia-treated animals were housed in normobaric hypoxic tent containing 11.3% oxygen for consecutive 4 weeks. The exercise-trained animals were exercised on a motor-driven rodent treadmill at a speed of 15 m/min, 5% grade for 60 min/day, 5 days per week for 4 weeks. The results showed that, compared with NC group, hypoxia attenuated complex I, II, IV and ATP synthase activities of the electron transport chain, and the level of mitochondrial membrane potential in HC group (P < 0.05 or P < 0.01). Moreover, hypoxia decreased mitochondrial OGG1, MnSOD, and GPx activities (P < 0.05 or P < 0.01), whereas elevated reactive oxygen species (ROS) generation and the level of 8-oxo-deoxyguanosine (8-oxodG) in mtDNA (P < 0.01). Furthermore, hypoxia attenuated muscle and mitochondrial [NAD⁺]/ [NADH] ratio, and SIRT3 protein expression (P < 0.05 or P < 0.01). Compared with HC group, exercise training in hypoxia elevated complex I, II, IV and ATP synthase activities, and the level of mitochondrial membrane potential in HT group (P < 0.05 or P < 0.01). Moreover, exercise training in hypoxia increased MnSOD and GPx activities and mitochondrial OGG1 level (P < 0.01), whereas decreased ROS generation and the level of 8-oxodG in mtDNA (P < 0.01). Furthermore, exercise training in hypoxia increased muscle and mitochondrial [NAD⁺]/[NADH] ratio, as well as SIRT3 protein expression (P < 0.05 or P < 0.01). These findings suggest that exercise training in hypoxia can decrease hypoxia-induced mtDNA oxidative damage in the skeletal muscle through up-regulating exercise-induced mitochondrial OGG1 and antioxidant enzymes. Exercise training in hypoxia may improve hypoxia tolerance in skeletal muscle mitochondria via elevating [NAD⁺]/[NADH] ratio and SIRT3 expression.

[Exercise and health: from evaluation of health-promoting effects of exercise to exploration of exercise mimetics]

Regular endurance exercise promotes favorable structure and metabolism adaptations in contracting organ (skeletal muscle) and "far-sited" organ (heart, brain, liver, adipose tissue). Exercise induced skeletal muscle remodeling by activating a series of signaling and transcriptional circuitry (e. g., PPARδ, AMPK, SIRT1 and PGC-1α). In addition, contracting skeletal muscle is an endocrine organ producing and releasing myokines (e. g. IL-6, BDNF and Irisin), which work in a hormone-like fashion, exerting specific endocrine effects on " far-sited" organ. It has been suggested that myokines may contribute to exercise-induced protection against several chronic disease. In this review, we discuss recent discoveries that raise the possibility of synthetically mimicking exercise with pathway-specific drugs to improve health.

Lymphatic drainage of the skull base: comparative anatomic and advanced imaging studies in the rabbit and human with implications for spread of nasopharyngeal carcinoma

This preliminary study investigated the lymphatic drainage and distribution of lymphatic structures in the skull base. Characteristics of the rabbit skull base were analyzed and compared correspondingly with those of the human skull. The lymphatic circulation in the rabbit cranial base was detected by digital subtraction angiography (DSA), and lymph drainage in the human skull base was illustrated by interstitial magnetic resonance lymphography (MRL). Lymphatic structures and their distribution in MRL were identified by comparing with contrast-enhanced MRI and clinical data on basilar metastasis of nasopharyngeal carcinoma (NPC) in the human skull base. Anatomic similarity was found between the rabbit and human basilar regions. Well-visualized lymphatic pathways were found in the rabbit cranial base, and human lymphatic structures showed high signal intensity in enhanced T1-weighted MRL images. Lymphatic tissues in the human basilar region were found mainly distributed in the areas of the jugular foramen, foramen lacerum, and petrosal section of the internal carotid artery (ICA). Their distribution in the human basilar region was similar to the distribution in the rabbit basilar region and consistent with our clinical findings of the predilection sites of NPC metastasis in the skull base. Our studies show that bilateral symmetrical lymphatic structures were distributed along the ICA, internal jugular vein, and dura of cranial base in the central part of the middle and posterior skull base.

Redefining the role of mitochondria in exercise: a dynamic remodeling

Exercise induced adaptations in muscle are highly specific and dependent upon the type of exercise, as well as its frequency, intensity, and duration. Mitochondria are highly dynamic organelles. Fusion and fission reactions lead to a continuous remodeling of the mitochondrial network, which range from reticulum of elongated and branched filaments to collections of individual organelles. Mitochondrial network dynamics are sensitive to various physiological and pathological stimuli, and mitochondrial morphological changes are no epiphenomena, but central to cell function and survival. There is a strong correlation between mitochondrial network morphology, dynamic-related protein, and energy metabolism. It is expected that alteration in cellular energy status during exercise can also be achieved through mitochondrial network dynamics. In this review, we describe mitochondrial network remodeling response to acute and endurance exercise, which is accompanied by bioenergetics and redox regulation. In addition, potential mechanisms for metabolic and redox signaling involved in mitochondrial dynamic regulation are also reviewed.

Resveratrol induces mitochondrial DNA repair enzyme downregulation and promotes pancreatic acinar cell apoptosis in rats with severe acute pancreatitis

AIM: To investigate the relationship among pancreatic acinar cell apoptosis, mitochondrial apoptosis pathway and mitochondrial DNA repair enzyme in severe acute pancreatitis (SAP).

METHODS: Thirty Sprague-Dawley rats were randomly divided into sham operation group (n = 10), model control group (SAP rats induced by retrograde injection of sodium taurocholate, n = 10), and resveratrol treatment group (SAP rats injected with resveratrol, n = 10). Serum amylase and caspase-3 and -9 activity in pancreatic acinar cells were detected. The level of 8-oxodeoxyguanosine (8-oxodG) in mitochondrial DNA (mtDNA) was measured by high-pressure liquid chromatography (HPLC). Mitochondrial cross-membrane potential (ΔΨ) was measured by monitoring the fluorescence spectrum of rhodamine 123. Pancreatic acinar cell apoptosis was detected by flow cytometry. Cytochrome c release and mitochondrial 8-oxoguanine DNA glycosylase 1 (OGG1) protein expression were determined by Western blot. Pathological damage of pancreatic tissue was scored.

RESULTS: Serum amylase level, mitochondrial cross-membrane potential, mitochondrial OGG1 protein expression level and pancreatic pathological score were lower in the resveratrol treatment group than in the model control group (4761.98 ± 501.45 vs 7428.91 ± 526.49, 18.42 ± 2.04 vs 22.01 ± 2.93, 73.97 ± 6.49 vs 159.46 ± 12.85, and 5.74 ± 0.95 vs 12.95 ± 1.54, respectively; all P < 0.05). Pancreatic acinar cell apoptosis index, cytochrome c release, 8-oxodG level and caspase-3 and -9 activity were higher in the resveratrol treatment group than in the model control group (19.63 ± 2.07 vs 12.45 ± 1.93, 174.31 ± 15.93 vs 100 ± 0.00, 0.0590 ± 0.074 vs 0.0336 ± 0.0061, 2.37 ± 0.35 vs 1.95 ± 0.19, and 2.07 ± 0.25 vs 1.62 ± 0.15, respectively; all P < 0.05).

CONCLUSION: Resveratrol can reduce pancreatic pathological damage in SAP rats possibly by downregulating mitochondrial OGG1 protein expression and inducing pancreatic acinar cell apoptosis.

Elevated expression of transmembrane IL-15 in immune cells correlates with the development of murine lupus: a potential target for immunotherapy against SLE

Presentation in trans by the Interleukin-15 receptor alpha chain (IL-15Ralpha) has been suggested as the main mechanism for IL-15 anchoring to the cell surface, but it is also evident that IL-15 can exist as a transmembrane protein. We herein demonstrate that replacement of the first 41 residues of human IL-15 (hIL-15) with Igkappa chain leader sequence resulted in secretion of most of the recombinant hIL-15 expressed in transfectant cells, thus identifying the transmembrane region of IL-15. A fusion protein (hIL-15Ralpha-Fc) between the extracellular domain of hIL-15Ralpha and the Fc fragment of IgG1 was prepared and shown to be able to bind with transmembrane IL-15 (tmIL-15). The level of tmIL-15 expression in macrophages, activated T cells and B cells from 6-month-old BXSB male mice, an animal model for systemic lupus erythematosus (SLE), was significantly increased compared with that from BXSB females or young males. In addition, hIL-15Ralpha-Fc was able to block the T cell stimulating and anti-apoptotic effect of the tmIL-15-positive BXSB macrophages in vitro. Intravenous administration of hIL-15Ralpha-Fc reduced the titre of autoantibodies against dsDNA and also proteinuria in aged BXSB males, implying that neutralization of IL-15 activity in vivo may be an effective way of treating SLE.

Upregulation of uncoupling protein-3 in skeletal muscle during exercise: a potential antioxidant function

Uncoupling protein-3 (UCP3) expression has been shown to increase dramatically in response to muscular contraction, but the physiological significance of UCP3 upregulation is still elusive. In this study, UCP3 mRNA and protein expression were investigated along with mitochondrial respiratory function, reactive oxygen species (ROS) generation, and antioxidant defense in rat skeletal muscle during and after an acute bout of prolonged exercise. UCP3 mRNA expression was elevated sharply at 45 min of exercise, reaching 7- to 8-fold above resting level at 150 min. The increase in UCP3 protein content showed a latent response but was elevated approximately 1.9-fold at 120 min of exercise. Both UCP3 mRNA and UCP3 protein gradually returned to resting levels 24 h postexercise. Mitochondrial ROS production was progressively increased during exercise. However, ROS showed a dramatic drop at 150 min although their levels remained severalfold higher during the recovery. Mitochondrial State 4 respiration rate was increased by 46 and 58% (p < 0.05) at 90 and 120 min, respectively, but returned to resting rate at 150 min, when State 3 respiration and respiratory control index (RCI) were suppressed. ADP-to-oxygen consumption (P/O) ratio and ATP synthase activity were lowered at 3 h postexercise, whereas proton motive force and mitochondrial malondialdehyde content were unchanged. Manganese superoxide dismutase gene expression was not affected by exercise except for an increase in mRNA abundance at 3 h postexercise. These data demonstrate that UCP3 expression in rat skeletal muscle can be rapidly upregulated during prolonged exercise, possibly owing to increased ROS generation. Increased UCP3 may partially alleviate the proton gradient across the inner membrane, thereby reducing further ROS production by the electron transport chain. However, prolonged exercise caused a decrease in energy coupling efficiency in muscle mitochondria revealed by an increased respiration rate due to proton leak (State 4/State 3 ratio) and decreased RCI. We thus propose that the compromise of the oxidative phosphorylation efficiency due to UCP3 upregulation may serve an antioxidant function to protect the muscle mitochondria from exercise-induced oxidative stress

Endurance training attenuates the bioenergetics alterations of rat skeletal muscle mitochondria submitted to acute hypoxia: role of ROS and UCP3

The physiological significance of skeletal muscle mitochondrial uncoupling protein 3 (UCP3) in hypoxia is elusive. In the current study, UCP3 mRNA and protein expressions were investigated along with mitochondrial respiratory function, reactive oxygen species (ROS) generation, as well as manganese superoxide dismutase (MnSOD) expression in rat skeletal muscle with or without endurance training after an acute and severe hypobaric hypoxia exposure for different time. Acute hypoxia induced a series of impairments in skeletal muscle mitochondrial bioenergetics. In untrained rats, UCP3 protein content increased by 60% above resting level at 4 h hypoxia, whereas MnSOD protein content and activity were unaltered. UCP3 upregulation increased mitochondrial uncoupling respiration thus reducing O2(.-) generation, but inevitably decreased ATP production. Training decreased acute hypoxia-induced upregulation of UCP3 protein (67% vs 42%) in rat skeletal muscle. ROS production in trained rats also showed a dramatic decrease at 2 h, 4 h and 6 h, respectively, compared with that in untrained rats. MnSOD protein contents and activities were significantly (50% and 34%) higher in trained than those in untrained rats. Training adaptation of MnSOD may enhance the mitochondrial tolerance to ROS production, and reduce UCP3 activation during severe hypoxia, thus maintaining the efficiency of oxidative phosphorylation. In trained rats, mitochondrial respiratory control (RCR) and P/O ratios were maintained relatively constant despite severe hypoxia, whereas in untrained rats RCR and P/O ratios were significantly decreased. These results indicate that (1) UCP3 mRNA and protein expression in rat skeletal muscle are upregulated during acute and severe hypobaric hypoxia, which may reduce the increased cross-membrane potential (Deltapsi) and thus ROS production; (2) Endurance training can blunt hypoxia-induced UCP3 upregulation, and improve mitochondrial efficiency of oxidative phosphorylation due to increased removal of ROS.

Regulation of mitochondrial uncoupling respiration during exercise in rat heart: role of reactive oxygen species (ROS) and uncoupling protein 2

The physiological significance of cardiac mitochondrial uncoupling protein 2 (UCP2)-mediated uncoupling respiration in exercise is unknown. In the current study, mitochondrial respiratory function, UCP2 mRNA level, UCP2-mediated respiration (UCR), and reactive oxygen species (ROS) generation, as well as manganese superoxide dismutase (MnSOD) activity were determined in rat heart with or without endurance training after an acute bout of exercise of different duration. In the untrained rats, state 4 respiration and UCR-independent respiration rates were progressively increased with exercise time and were 64 and 70% higher, respectively, than resting rate at 150 min, whereas UCR was elevated by 86% with no significant change in state 3 respiration. UCP2 mRNA level showed a 5- and 4-fold increase, respectively, after 45 and 90 min of exercise, but returned to resting level at 120 and 150 min. Mitochondrial ROS production and membrane potential (Deltapsi) increased progressively until 120 min, followed by a decrease to the resting level at 150 min. MnSOD mRNA abundance showed a 2-fold increase at 120 min but MnSOD activity did not change with exercise. Training significantly increased mitochondrial ATP synthetase activity, ADP to oxygen consumption (P/O) ratio, respiratory control ratio, and MnSOD activity, whereas exercise-induced state 4 respiration, UCR, ROS production, and Deltapsi were attenuated in the trained rats. We conclude that (1) UCP2 mRNA expression and activity in rat heart can be upregulated during prolonged exercise, which may reduce cross-membrane Deltapsi and thus ROS production; and (2) endurance training can blunt exercise-induced UCP2 and UCR, and improve mitochondrial efficiency of oxidative phosphorylation due to increased removal of ROS.

[Influence of the subglottic secretion drainage on the morbidity of ventilator associated pneumonia in mechanically ventilated patients]

OBJECTIVE

To assess the influence of the subglottic secretion drainage on the morbidity of ventilator associated pneumonia in mechanically ventilated patients.

METHODS

All cases requiring intubation in SICU were intubated with a special type endotracheal tube which has a small-bore cannula in its wall for subglottic secretion drainage. They were randomly divided into two groups received subglottic secretion drainage(SSD) and usual care(NON-SSD) respectively. Bacterial culture of samples from the oropharynx, subglottic secretions and lower respiratory tract were obtained periodically. The amount of subglottic secretion aspirated daily, ventilated days and the number of cases with VAP were recorded. Etiologic diagnosis of VAP was based on the quantitative bacterial culture of secretions obtained by protected specimen brush(PSB).

RESULTS

The morbidity of VAP in the SSD group (n = 35) (23%) was lower than that in the NON-SSD group (n = 33) (45%) (P < 0.05). The difference was due to the significant reduction of VAP caused by gram-positive cocci and Haemophilus influenzae organisms. However, no difference was observed in the incidence of VAP caused by non-fermental bacteria. After intubation the onset of VAP was delayed in SSD group (14 +/- 8 day) as compared with the NON-SSD group (6 +/- 4 day) (P < 0.05). The same organisms were isolated by PSB among 61% (14/23) patients with VAP as what were previously isolated from the subglottic secretions.

CONCLUSIONS

The presence of subglottic secretion may be an origin of the pathogenetic organisms of VAP. The morbidity of VAP in mechanically ventilated patients can be reduced by SSD, especially for VAP caused by gram-positive cocci and Haemophilus influenzae organisms. SSD may be a simple and effective method for prevention of VAP.

[Observation of biofilms inside tracheal tubes by electron microscopy and the relationship between biofilms and VAP]

OBJECTIVE

To observe the formation of biofilms inside tracheal tubes and to evaluate the effect of biofilm on the development of ventilator associated pneumonia (VAP).

METHODS

Biofilms inside tracheal tubes from intubated patients were observed by scanning electron microscopy and transmission electron microscopy, meanwhile bacteria were detected in the specimens from the lower respiratory tract and the inside of tracheal tubes.

RESULTS

76% (19/25) of inner surface of tracheal tubes was coated with a confluent amorphous matrix by scanning electron microscopy. The average duration of trach-intubation in this group [(10.7 +/- 7.9) days] was longer than that in the other group [(2.1 +/- 0.8) days] in which tracheal tubes were not coated with the confluent amorphous matrix (P < 0.05). The presence of many bacteria(14/18) within these amorphous matrix was confirmed by transmission electron microscopy. Of the sixteen tracheal tubes, eleven tubes grew the same organisms that had been isolated from the secretions of the lower respiratory tract before extubation. In some VAP patients (7/8), organisms isolated from tracheal tubes were the same organisms which were pathogenic organisms of VAP.

CONCLUSIONS

There was a close connection between the formation of bacterial BF and the long-term indwelling tracheal tubes. The presence of bacterial BF in the inner of tracheal tubes might be associated with the pathogenic organisms of VAP.

Heart rate variability following cardiac surgery fails to predict short-term cardiovascular instability

The heart rate variability of 40 patients has been examined by spectral analysis following cardiac surgery. The heart rate variability was measured upon patient arrival in ICU in both a resting supine position, and following passive straight-leg raising. After 12 hours in ICU, the patients were classified as having been cardiovascularly stable or unstable according to a specially devised inventory. Their heart rate variability data was then examined to seek any predictor of instability. Passive straight-leg raising induced a decrease in spectral power across all of the component frequency bands. The LF/HF ratio rose with passive straight-leg raising, but failed to reach significance. None of these changes were sustained. There was no significant difference in heart rate variability patterns between the stable and unstable groups, and so no predictor was identified. Initial clinical assessment was also studied, and it too provided no reliable prediction of short-term cardiovascular instability.

Variability of R-R, P wave-to-R wave, and R wave-to-T wave intervals

We analyzed the effect of changing posture from supine to standing on the variability of R-R, P-R, and R-T intervals in 10 healthy volunteers using power spectral analysis. An electrocardiogram and respiratory trace were recorded before and after posture change. Variability in the P-R and R-T intervals was much less than in the R-R interval and demonstrated a lower-frequency (LF)-to-high-frequency (HF) ratio. Changing from a supine to a standing position showed no change in indexes of vagal influence on the P-R and R-T variability, in contrast to the well-documented decrease in the indexes of vagal influence on the R-R variability (HF power decreased from 2.33 to 0.41 ms2, P = 0.003; amplitude of the respiration-to-heart rate impulse response decreased from 31.6 to 14.4 ms.ml-1.s-1, P = 0.03; and LF/HF increased from 1.96 to 5.22, P = 0.005). We concluded from this study that the effects of standing were an observed reduction in vagal influence on the heart rate variability of the R-R interval and maintenance of lung volume-related vagal modulation of the P-R and R-T intervals.