Too much or not enough of a good thing — The Janus faces of autophagy in cardiac fuel and protein homeostasis

Cells respond to changes in their environment and in their intracellular milieu by altering specific pathways of protein synthesis and degradation. Autophagy is a highly conserved catabolic process involved in the degradation of long-lived proteins, damaged organelles, and subcellular structures. The process is orchestrated by the autophagy related protein (Atg) to form the double-membrane structure autophagosomes, which then fuse with lysosomes to generate autophagolysosomes where subcellular contents are degraded for a variety of cellular processes. Alterations in autophagy play an important role in diseases including cancer, neurodegenerative diseases, aging, metabolic diseases, inflammation and cardiovascular diseases. In the latter, dysregulated autophagy is speculated to contribute to the onset and development of atherosclerosis, ischemia/reperfusion injury, cardiomyopathy, diabetes mellitus, and hypertension. Autophagy may be both adaptive and beneficial for cell survival, or maladaptive and detrimental for the cell. Basal autophagy plays an essential role in the maintenance of cellular homeostasis whereas excessive autophagy may lead to autophagic cell death. The point and counterpoint discussion highlights adaptive vs. maladaptive autophagy. In this review, we discuss the molecular control of autophagy, focusing particularly on the regulation of physiologic vs. defective autophagy.     

<Emphasis Type="Italic">Chlamydia pneumoniae</Emphasis> Infections in Asthma

Chlamydia pneumoniae is an intracellular pathogen that has been suggested to play a role in the pathology of asthma. However, so far none of the studies have provided clear evidence for a causative role of C. pneumoniae infections in asthma, although there is little doubt that chronic C. pneumoniae infection does aggravate asthma and should be treated.The diagnosis of C. pneumoniae infection is still a matter of concern for it is dependent on trained skilled personnel and can vary significantly between different diagnostic laboratories. This fact is also one of the major problems encountered when comparing epidemiological studies investigating the possible role of C. pneumoniae infections and their impact on the pathogenesis of other diseases.With regard to therapy, long-term treatment with macrolides is the best available method to eradicate C. pneumoniae. Successful therapy for C. pneumoniae, however, can also be complicated by the high possibility of de novo infection as epidemiological studies have shown that the prevalence of antibodies to C. pneumoniae increases with age in all populations studied. In the northern hemisphere the prevalence of C. pneumoniae is also affected by seasonal conditions. It is too early to draw any conclusions from the equatorial belt countries. The available data on C. pneumoniae in tropical countries indicate a much faster infection rate during early adulthood with 100% serological prevalence at an age greater than 25 years. This data, if confirmed, would argue against C. pneumoniae causing asthma since the asthma prevalence in those countries does not increase in a parallel pattern.An alternative interpretation of most studies could be that the increased rate of C. pneumoniae infections in patients with asthma results from a modified susceptibility towards the microorganism, due to yet unknown changes of the host cell’s physiology. It should be kept in mind that increased prevalence of C. pneumoniae infection is not restricted to asthma.Further studies are needed to understand the role of C. pneumoniae, especially of chronic infection, in the pathogenesis of inflammatory diseases with a specific focus on the effect that the microorganism triggers in the infected host cell. Only when we understand what C. pneumoniae does to its host cell will we be able to judge its impact on the overall status of an affected patient, and this knowledge will help us to develop a successful therapy.     

The Microbiome in Obesity,Diabetes, and NAFLD: What is Your Gut Telling Us?

The gut microbiota has considerable complexity and is influenced by multiple factors including host genetics and diet as well as metabolic diseases such as obesity, diabetes, and nonalcoholic fatty liver disease (NAFLD). Despite animal studies demonstrating the gut microbiota may play a significant pathogenic role in these conditions, the exact mechanisms and host-bacterial interactions responsible remain cryptic. Reductions in the relative abundance of bacteria Clostridium leptum and coccoides groups, including Roseburia and Eubacterium spp. and Faecalibacterium prausnitzii, are implicated to protect against obesity and diabetes. The mucin-utilizing bacterium Akkermansia muciniphila has also been shown in animal models to have “protective” effects against obesity. Similarly, in animal and clinical studies of NAFLD, increased levels of Ruminococcus and Escherichia spp. have been documented, although their overall significance is unclear. Constraints in our understanding of cause- versus consequence relationships may be overcome in the future by utilizing “rationally designed” microbial consortia in small animal models.     

The search for putative unifying genetic factors for components of the metabolic syndrome

Aims/hypothesis

The metabolic syndrome is a cluster of factors contributing to increased risk of cardiovascular disease and type 2 diabetes but unifying mechanisms have not been identified. Our aim was to study whether common variations in 17 genes previously associated with type 2 diabetes or components of the metabolic syndrome and variants in nine genes with inconsistent association with at least two components of the metabolic syndrome would also predict future development of components of the metabolic syndrome, individually or in combination.

Methods

Genetic variants were studied in a large prospective study of 16,143 non-diabetic individuals (mean follow-up time 23 years) from the Malmö Preventive Project. In this study, development of at least three of obesity (BMI?≥?30 kg/m²), dyslipidaemia (triacylglycerol?≥?1.7 mmol/l and/or lipid-lowering treatment), hypertension (blood pressure?≥?140/90 mmHg and/or antihypertensive medication) and hyperglycaemia (fasting plasma glucose?≥?5.6 mmol/l and/or known diabetes) was defined as development of the metabolic syndrome. The risk of developing at least three components of the metabolic syndrome or the individual components was calculated by logistic regression adjusted for age at baseline, follow-up time and sex.

Results

Polymorphisms in TCF7L2 (rs7903146, OR 1.10, 95% CI 1.04–1.17, p?=?0.00097), FTO (rs9939609, OR 1.08, 95% CI 1.02–1.14, p?=?0.0065), WFS1 (rs10010131, OR 1.07, 95% CI 1.02–1.13, p?=?0.0078) and IGF2BP2 (rs4402960, OR 1.07, 95% CI 1.01–1.13, p?=?0.021) predicted the development of at least three components of the metabolic syndrome in both univariate and multivariate analysis; in the case of TCF7L2, WFS1 and IGF2BP this was due to their association with hyperglycaemia (p?p?=?0.0033 and p?=?0.027, respectively) and for FTO it was due to its association with obesity (p?=?0.004). A polymorphism in the GCKR gene predicted dyslipidaemia (rs1260326, OR 1.15, 95% CI 1.09–1.22, p?p?p?p?

Conclusions/interpretation

Polymorphisms in susceptibility genes for type 2 diabetes (TCF7L2, WFS1, IGF2BP2) and obesity (FTO) predispose to the metabolic syndrome by increasing the risk of one specific component of the metabolic syndrome. The findings argue against a unifying genetic component for the metabolic syndrome.

     

Identification of Biomarkers for <Emphasis Type="Italic">Schistosoma</Emphasis>-Associated Pulmonary Arterial Hypertension Based on RNA-Seq Data of Mouse Whole Lung Tissues

Background

Pulmonary arterial hypertension (PAH) is a deadly disease, and the molecular mechanism of PAH has not been clarified clearly. The objective of this study was to identify possible biomarkers and explore the potential mechanisms of Schistosoma-induced PAH.

Methods

GSE49114 RNA-Seq data developed from mouse whole lung tissues were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) between control samples and schistosomiasis-induced PAH samples were identified by the edgeR software. Gene Ontology (GO) and pathway enrichment analysis of DEGs were performed, followed by metabolic pathway network construction. Moreover, pathways with higher connectivity degrees in the metabolic pathway network were identified.

Results

Totally, 877 up- and 520 downregulated DEGs were screened. The upregulated DEGs such as IL-4 (Interleukin-4) were significantly related with immune system process, transmembrane signaling receptor activity, and signal transducer activity. Downregulated DEGs (i.e., Smad9 (SMAD family member 9), BMPR2 (bone morphogenetic protein type 2 receptor), and Eng (endoglin)) were significantly enriched in signal transducer activity, growth factor binding, and signal transduction. The top 10 metabolic pathways with highest connectivity degree were screened, including leishmaniasis (degree?=?26), antigen processing and presentation (degree?=?20), hematopoietic cell lineage (degree?=?20), chemokine signaling pathway (degree?=?18), and JAK–STAT signaling pathway (degree?=?18).

Conclusions

Smad9, BMPR2, Eng and IL4, and their relative functions such as signal transduction, signal transducer activity, and immune system process might play important roles in schistosomiasis-induced PAH. Moreover, the interaction of metabolic pathways was critical in the development of schistosomiasis-PAH.

     

Longevity-modulating effects of symbiosis: insights from <Emphasis Type="Italic">Drosophila</Emphasis>–<Emphasis Type="Italic">Wolbachia</Emphasis> interaction

Microbial communities are known to significantly affect various fitness components and survival of their insect hosts, including Drosophila. The composition of symbiotic microbiota has been shown to change with the host’s aging. It is unclear whether these changes are caused by the aging process or, vice versa, they affect the host’s aging and longevity. Recent findings indicate that fitness and lifespan of Drosophila are affected by endosymbiotic bacteria Wolbachia. These effects, however, are inconsistent and have been reported both to extend and shorten longevity. The main molecular pathways underlying the lifespan-modulating effects of Wolbachia remain unclear, however insulin/insulin-like growth factor, immune deficiency, ecdysteroid synthesis and signaling and c-Jun N-terminal kinase pathways as well as heat shock protein synthesis and autophagy have been proposed to play a role. Here we revise the current evidence that elucidates the impact of Wolbachia endosymbionts on the aging processes in Drosophila.     

Genetics of Gestational Diabetes Mellitus and Maternal Metabolism

Gestational diabetes mellitus (GDM) is defined as abnormal glucose tolerance with onset or first recognition during pregnancy. Women with a history of GDM are at long-term risk for developing type 2 diabetes (T2DM), raising the question to what extent GDM and T2DM share a common genetic architecture. Meta-analysis of candidate gene studies and genome-wide association analysis (GWAS) have identified a number of genes which are reproducibly associated with GDM, including TCF7L2, GCK, KCNJ11, KCNQ1, CDKAL1, IGF2BP2, MTNR1B, and IRS1. These genes are also associated with T2DM. Candidate gene and GWAS have also identified genes associated with maternal metabolic traits, most of which are also associated with metabolic traits in the general population. Two genes, BACE2 and HKDC1, are uniquely associated with maternal metabolic traits. These studies suggest that there are similarities and differences between the genetic architecture of GDM and T2DM and metabolic quantitative traits in pregnant and non-pregnant populations.     

Molekulargenetische Grundlagen der zystischen Fibrose als Beispiel genetischer Erkrankungen in der Pneumologie

The generalized exocrinopathy cystic fibrosis (CF) is caused by molecular lesions in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The basic defect of this autosomal-recessive disorder manifests in decreased permeability for chloride ions across the apical epithelial membrane. Of the more than 1,000 known CFTR mutations the most frequent mutation F508del occurs on about 70% of North- and Mideuropean CF chromosomes. CFTR mutations are also causatively involved in male infertility, pancreatitis and several airway diseases like disseminated bronchiectasis. The differential diagnosis between CF, other CFTR -opathies and diseases of unrelated etiology can be achieved by the assessment of clinical symptoms, CFTR mutation analysis and electrophysiological bioassays (sweat test, nasal potential difference, intestinal current measurements).     

Role of hypothalamic autophagy in the control of whole body energy balance

Autophagy is a catabolic process involving the rearrangement of subcellular membranes to sequester cytoplasm and organelles for delivery to lysosomes, where the sequestered material is degraded and recycled. Autophagy is important for maintenance of intracellular energy homeostasis and the quality control of organelles such as the endoplasmic reticulum (ER) and mitochondria, which suggests that dysregulated autophagy might play a role in the pathogenesis of metabolic disorders and diabetes. In an attempt to elucidate the role of autophagy in metabolic disorders, diverse in vivo and in vitro models have been employed. Site-specific autophagy knockout models that are autophagy-deficient specifically in pancreatic β-cells, skeletal muscle, adipose tissues or liver have been produced. These models have generated valuable information regarding the role of autophagy in body metabolism. The role of autophagy in the hypothalamus, which controls whole body energy balance, appetite and energy expenditure, has also been investigated. Thus, mice with autophagy deficiency in the hypothalamus have shown diverse phenotypes (lean vs. obese) depending on the site of autophagy deficiency or the method of autophagy abrogation.     

Interactions of <Emphasis Type="Italic">GST</Emphasis> Polymorphisms in Air Pollution Exposure and Respiratory Diseases and Allergies

Purpose of Review

The purpose of this review is to summarize the evidence from recently published original studies investigating how glutathione S-transferase (GST) gene polymorphisms modify the impact of air pollution on asthma, allergic diseases, and lung function.

Recent Findings

Current studies in epidemiological and controlled human experiments found evidence to suggest that GSTs modify the impact of air pollution exposure on respiratory diseases and allergies. Of the nine articles included in this review, all except one identified at least one significant interaction with at least one of glutathione S-transferase pi 1 (GSTP1), glutathione S-transferase mu 1 (GSTM1), or glutathione S-transferase theta 1 (GSTT1) genes and air pollution exposure. The findings of these studies, however, are markedly different. This difference can be partially explained by regional variation in the exposure levels and oxidative potential of different pollutants and by other interactions involving a number of unaccounted environment exposures and multiple genes.

Summary

Although there is evidence of an interaction between GST genes and air pollution exposure for the risk of respiratory disease and allergies, results are not concordant. Further investigations are needed to explore the reasons behind the discordancy.

     

Lymphoid hyperplasia of the colon and its association with underlying allergic airway diseases

Purpose

The purpose of this study was to determine the prevalence of lymphoid hyperplasia in the lower gastrointestinal tract and its role in patients undergoing colonoscopic examinations, particularly focusing on any allergic predisposition.

Methods

A database search performed at the Department of Gastroenterology at Onomichi Municipal Hospital identified seven patients with lymphoid hyperplasia in the large intestine (i.e., cecum, colon, and/or rectum). Data regarding the endoscopic, biological, and pathological examinations performed and the allergic histories for each patient were retrospectively reviewed from the clinical records.

Results

Median age of the patients (four males, three females) was 50 years. Lymphoid hyperplasia was seen in the cecum (n?=?5), ascending colon (n?=?2), and transverse colon (n?=?1). Six patients (85.7 %) had one of the allergic airway diseases: allergic rhinoconjunctivitis for pollen (n?=?3), bronchial asthma (n?=?1), infantile asthma (n?=?1), or allergic bronchitis (n?=?1). Drug allergy (n?=?3) and urticaria (n?=?2) were also found. All seven patients had one or more allergic diseases; however, none had a history of food allergy. Blood tests for allergens revealed that six patients (85.7 %) had positive reactions to inherent allergens, whereas only one patient had a positive reaction to food allergens.

Conclusions

Our results indicate that lymphoid hyperplasia in the large intestine may be associated with allergic airway diseases rather than with food allergies; thus, its presence may be useful to detect patients with underlying airway hyperreactivity.

     

<Emphasis Type="Italic">Fas/FasL,Bcl2</Emphasis> and <Emphasis Type="Italic">Caspase</Emphasis>-<Emphasis Type="Italic">8</Emphasis> gene polymorphisms in Chinese patients with rheumatoid arthritis

Apoptosis signals are necessary for maintaining homeostasis and an adequate immune response. Dysregulation of apoptosis-related genes in the immune system has an important impact on autoimmune diseases such as rheumatoid arthritis (RA). Thus, we investigated the association between Fas rs2234767 G/A, FasL rs763110 C/T, Bcl2 rs12454712 T/C, Bcl2 rs17757541 C/G, and Caspase-8 rs1035142 G/T polymorphisms and RA susceptibility in a Chinese population. These five single-nucleotide polymorphisms (SNPs) were studied in a Chinese population consisting of 615 patients with RA and 839 controls. Genotyping was performed using a custom-by-design 48-Plex SNP scan TM kit. Furthermore, we undertook a meta-analysis between FasL rs763110 C/T and RA. This study indicated that Fas rs2234767 and Bcl2 rs17757541 polymorphisms were risk factors for RA. No association was observed between FasL rs763110 C/T, Bcl2 rs12454712 T/C, and Caspase-8 rs1035142 G/T polymorphisms and RA in this study. The results of this meta-analysis suggested no significant association between FasL rs763110 C/T and RA. However, stratification analysis of this meta-analysis indicated that FasL rs763110 C/T increased the risk of Caucasian RA patients. In conclusion, this study demonstrated that Fas rs2234767 G/A and Bcl2 rs17757541 T/C polymorphisms might be associated with an increased risk of RA. This meta-analysis revealed that FasL rs763110 C/T was associated with an increased risk of Caucasian RA patients.     

Familial aggregation of albuminuria and arterial hypertension in an Aboriginal Australian community and the contribution of variants in <Emphasis Type="Italic">ACE</Emphasis> and <Emphasis Type="Italic">TP53</Emphasis>

Background

Aboriginal Australians are at high risk of cardiovascular, metabolic and renal diseases, resulting in a marked reduction in life expectancy when compared to the rest of the Australian population. This is partly due to recognized environmental and lifestyle risk factors, but a contribution of genetic susceptibility is also likely.

Methods

Using results from a comprehensive survey of one community (N?=?1350 examined individuals), we have tested for familial aggregation of plasma glucose, arterial blood pressure, albuminuria (measured as urinary albumin to creatinine ratio, UACR) and estimated glomerular filtration rate (eGFR), and quantified the contribution of variation at four candidate genes (ACE; TP53; ENOS3; MTHFR).

Results

In the subsample of 357 individuals with complete genotype and phenotype data we showed that both UACR (h²?=?64%) and blood pressure (sBP h²?=?29%, dBP, h²?=?11%) were significantly heritable. The ACE insertion-deletion (P?=?0.0009) and TP53 codon72 polymorphisms (P?=?0.003) together contributed approximately 15% of the total heritability of UACR, with an effect of ACE genotype on BP also clearly evident.

Conclusions

While the effects of the ACE insertion-deletion on risk of renal disease (especially in the setting of diabetes) are well recognized, this is only the second study to implicate p53 genotype as a risk factor for albuminuria - the other being an earlier study we performed in a different Aboriginal community (McDonald et al., J Am Soc Nephrol 13: 677-83, 2002). We conclude that there are significant genetic contributions to the high prevalence of chronic diseases observed in this population.

     

Coughing Precipitated by <Emphasis Type="Italic">Bordetella pertussis</Emphasis> Infection

Infections with the gram-negative bacteria Bordetella pertussis (B. pertussis) have long been recognized as a significant threat to children and are increasingly recognized as a cause of cough in adolescents and adults. Antibiotic therapy, when administered during the virulent stages of the disease, can reduce the duration and severity of symptoms. Unfortunately, there are no effective treatments for the persistent coughing that accompanies and follows the infection. The pathogenesis of B. pertussis infection is briefly reviewed. Also discussed is the evidence supporting the hypothesis that the inflammatory peptide bradykinin may be responsible for the persistent, paroxysmal coughing associated with B. pertussis-initiated illness.     

Autophagy and hippocampal neuronal injury

Background

Autophagy is a specific universal biological phenomenon in eukaryotic cells, which is characterized by cytoplasmic vacuoles in the process of degrading cellular contents in lysosomes. The hippocampus plays an important role in higher nervous activities such as emotional integration, cognition, and memory. As an area closely related to learning and memory functions of the brain, the hippocampus is particularly sensitive to injuries caused by various reasons.

Purpose

Autophagy has certain links with a variety of causes of hippocampal neuronal injury. This short review discusses and summarizes this correlation with a focus on the possible role of autophagy and mechanisms in it.

Conclusion

The current correlation between autophagy and hippocampal neuronal injury has not been completely determined by the general public alike. Further studies are needed to determine special effects of autophagy on hippocampal neuronal injury, which might accelerate the development of therapeutic interventions in hippocampal neuronal injury in many neurological disorders.     

Accumulation of glycated proteins suggesting premature ageing in lamin B receptor deficient mice

Accumulation of advanced glycation end products (AGEs) is accompanied by increased free radical activity which contributes to ageing and the development or worsening of degenerative diseases. Apart from other physiological factors, AGEs are also an important biomarker for premature ageing. Here we report protein modifications (glycation) in a mouse model of lamin B receptor deficient ic ^J /ic ^J mice displaying skin defects similar to those of classical progeria. Therefore, we analysed AGE-modifications in protein extracts from various tissues of ic ^J /ic ^J mice. Our results demonstrated that pentosidine as well as argpyrimidine were increased in ic ^J /ic ^J mice indicating a modification specific increase in biomarkers of ageing, especially derived from glycolysis dependent methylglyoxal. Furthermore, the expression of AGE-preventing enzymes (Glo1, Fn3k) differed between ic ^J /ic ^J and control mice. The results indicate that not only lamin A but also the lamin B receptor may be involved in ageing processes.     

Loss of autophagy causes a synthetic lethal deficiency in DNA repair

(Macro)autophagy delivers cellular constituents to lysosomes for degradation. Although a cytoplasmic process, autophagy-deficient cells accumulate genomic damage, but an explanation for this effect is currently unclear. We report here that inhibition of autophagy causes elevated proteasomal activity leading to enhanced degradation of checkpoint kinase 1 (Chk1), a pivotal factor for the error-free DNA repair process, homologous recombination (HR). We show that loss of autophagy critically impairs HR and that autophagy-deficient cells accrue micronuclei and sub-G1 DNA, indicators of diminished genomic integrity. Moreover, due to impaired HR, autophagy-deficient cells are hyperdependent on nonhomologous end joining (NHEJ) for repair of DNA double-strand breaks. Consequently, inhibition of NHEJ following DNA damage in the absence of autophagy results in persistence of genomic lesions and rapid cell death. Because autophagy deficiency occurs in several diseases, these findings constitute an important link between autophagy and DNA repair and highlight a synthetic lethal strategy to kill autophagy-deficient cells.The preservation of genome integrity is critical for the prevention of human disease. In addition, the maintenance of proteome integrity is also considered central to healthy cellular homeostasis. Macroautophagy, hereafter referred to as autophagy, is a process that is paramount in counteracting damage to cytoplasmic constituents (1). Upon initiation of autophagy, double-membraned vesicles termed “autophagosomes” form to encapsulate cargoes including damaged or misfolded proteins and organelles. These vesicles ultimately fuse with lysosomes and the acidic hydrolases provided by the lysosome degrade cargoes into constituent parts, which can be recycled into biosynthetic pathways or in some situations, further catabolized to produce energy for the cell (1). Autophagy functions at basal levels in virtually all cells and is a major mechanism for protein turnover and the only known mechanism for degradation of organelles (1). Due to its crucial role in maintaining cytoplasmic and therefore cellular homeostasis, perturbations in autophagy have been reported to be an important contributing factor in a spectrum of diseases, including Crohn’s disease, lysosomal storage disorders, neurodegenerative diseases, and cancer (2–6).Autophagy operates in the cytoplasm and yet studies have shown that autophagy-deficient cells accumulate DNA damage (5). The reasons behind this observation, however, are not completely clear. Because the cellular environment of autophagy-deficient cells will cause accrual of damaged proteins with abnormal function and as a result accumulation of reactive oxygen species, it is easily conceivable that this will ultimately lead to a higher incidence of genetic lesions. However, even when autophagy is competent, our cells are already subject to an extremely high frequency of spontaneous DNA damage. The fact that this damage does not persist is due to highly efficient processes of DNA repair that serve to maintain genomic integrity (7, 8). We hypothesized, therefore, that the accumulation of genetic lesions in autophagy-deficient cells may be critically driven by a defect in DNA repair. We show that loss of autophagy leads to decreased levels of checkpoint kinase 1 (Chk1) and a greatly diminished ability to repair DNA double-strand breaks by homologous recombination (HR). As a result, autophagy-deficient cells are more reliant on nonhomologous end joining (NHEJ) for DNA repair, which uncovers a unique synthetic lethality-based strategy to kill cells that may be applicable to the treatment of various forms of human disease.