Human mitochondrial DNA diseases

The mitochondrial encephalomyopathies are a genetically heterogeneous group of disorders associated with impaired oxidative phosphorylation. Patients may exhibit a wide range of clinical symptoms and experience significant morbidity and mortality. There is currently no curative treatment. At present the majority of genetically defined mitochondrial encephalomyopathies are caused by mutations in mitochondrial DNA. The underlying molecular mechanisms and the complex relationship between genotype and phenotype in these mitochondrial DNA diseases remain only partially understood. We describe the key features of mitochondrial DNA genetics and outline some of the common disease phenotypes associated with mtDNA defects. A classification of pathogenic mitochondrial DNA point mutations which may have therapeutic implications is outlined.     

Drugs for rare diseases: mixed assessment in Europe

(1) Worldwide, there are an estimated 6000 to 7000 rare diseases. Patients face special difficulties in obtaining an accurate diagnosis, adequate information about the disease, and access to qualified specialists. (2) Drug companies do not spontaneously conduct research on drugs for rare diseases, mainly because of the limited market for each indication. Only a few dozen of these drugs were available in France before 2000. (3) In 2000 the European Union adopted a Regulation, based on experience in the United States, aimed at promoting the development of drugs for patients suffering from rare diseases, i.e. 'orphan drugs'. (4) In Europe, orphan drug status can be granted when the prevalence of the disease does not exceed 5 cases per 10 000 inhabitants (or when it is more frequent but profitability is likely to be inadequate). (5) Companies that market an orphan drug receive a variety of financial assistance as well as a 10-year marketing monopoly. (6) Between April 2000 and April 2005, 268 medicinal products received European orphan drug status and 22 were granted European marketing authorization. (7) Access to these drugs varies greatly from one European Union Member State to another, mainly because of the high annual treatment costs (up to 300 000 euros per patient). Worldwide sales of the orphan drug imatinib reached more than two thousand million dollars in 2005. (8) Our systematic analyses (see the New Products column of our French edition la revue Prescrire) show that only 5 drugs which received European orphan drug status before May 2005 were for diseases for which there had previously been no treatment. (9) Clinical evaluation of orphan drugs is hindered by the small number of patients available for clinical trials. Some orphan drugs are adequately tested before being brought to market. Others are not compared to existing treatments. In many cases, surrogate criteria are used instead of clinical endpoints. These methodological flaws are in no way limited to orphan drugs. (10) Not all orphan drugs represent therapeutic advances. Clinical research and evaluation should continue after marketing authorization has been granted. (11) More drugs, with better-documented efficacy and safety, are now available for patients who previously had no effective treatment options. Yet there is too much duplication and too little evaluation, and too many drugs are extremely expensive, meaning that patients in many European countries cannot benefit. And many rare diseases are still neglected.     

Role and treatment of mitochondrial DNA-related mitochondrial dysfunction in sporadic neurodegenerative diseases

Several sporadic neurodegenerative diseases display phenomena that directly or indirectly relate to mitochondrial function. Data suggesting altered mitochondrial function in these diseases could arise from mitochondrial DNA (mtDNA) are reviewed. Approaches for manipulating mitochondrial function and minimizing the downstream consequences of mitochondrial dysfunction are discussed.     

Drugs for the treatment of allergic diseases

Many kinds of drugs are used for the treatment of allergic diseases. Glucocorticoids are the most efficacious drugs and widely used for the treatment of allergic diseases. Recently, effectiveness of inhaled glucocorticoids for the treatment of bronchial asthma has been established. Beclomethasone dipropionate and fluticasone propionate, which are degraded easily after absorption, are applied by inhalation. Histamine is one of the most important mediators in allergic reactions and antihistamines have widely been applied for the treatment of allergic skin diseases. In Japan, over 20 antiallergic drugs, such as mediator release inhibitors, mediator antagonists and mediator synthesis inhibitors, have been developed. Recently developed compounds such as pranlukast and suplatast are very effective. To relieve the asthmatic attack, bronchodilators such as beta2-adrenoceptor agonists, theophylline and anti-cholinergic drugs are used. Clinical application of tacrolimus ointment has just started for the treatment of atopic dermatitis. Recently the number of allergic patients has increased. The onset and development of allergic diseases are considered to be dependent on both the genetic factors and the environmental factors. For the successful treatment of patients with allergic diseases, it is also important to consider the control of environmental factors.     

Targeting autophagy and mitophagy for mitochondrial diseases treatment

Introduction: Mitochondrial diseases are a group of rare genetic diseases with complex and heterogeneous origins which manifest a great variety of phenotypes. Disruption of the oxidative phosphorylation system is the main cause of pathogenicity in mitochondrial diseases since it causes accumulation of reactive oxygen species (ROS) and ATP depletion.

Areas covered: Current evidences support the main protective role of autophagy and mitophagy in mitochondrial diseases and other diseases associated with mitochondrial dysfunction.

Expert Opinion: The use of autophagy and/or mitophagy inducers may allow a novel strategy for improving mitochondrial function for both mitochondrial diseases and other diseases with altered mitochondrial metabolism. However, a deeper investigation of the molecular mechanisms behind mitophagy and mitochondrial biogenesis is needed in order to safely modulate these processes. In the coming years, we will also see an increase in awareness of mitochondrial dynamics modulation that will allow the therapeutic use of new drugs for improving mitochondrial function in a great variety of mitochondrial disorders.     

Drugs targeting mitochondrial functions to control tumor cell growth

Mitochondria, the power houses of the cell, are at the cross-road of many cellular pathways. They play a central role in energy metabolism, regulate calcium flux and are implicated in apoptosis. Mitochondrial dysfunctions have been associated with various physiopathological disorders, especially neurodegenerative diseases and cancer. Structurally diverse pharmacological agents have shown direct effects on mitochondria ultra-structures and functions, either at the DNA level or upon targeting proteins located in the inner or outer mitochondrial membranes. The brief review deals with the molecular targets and mechanisms of action of chemically diverse small molecules acting on specific mitochondrial loci, such as the respiratory chain, DNA biogenesis, potassium channels, the Bcl-2 protein and the permeability transition pores (PTP). Drugs, which specifically compromise the structural and functional integrity of mitochondria, may provide novel opportunities to combat cancer cell proliferation, providing that these molecules can be selectively delivered to tumor sites. Different examples reported here show that mitochondrial insult or failure can rapidly lead to inhibition of cell survival and proliferation. Mitochondrial impairment may be a successful anti-cancer strategy.     

Type 2 transglutaminase in neurodegenerative diseases: the mitochondrial connection

"Tissue" or type 2 Transglutaminase (TG2) is a peculiar multifunctional enzyme able to catalyse Ca(2+)-dependent post-translational modification of proteins, by establishing covalent bonds between peptide-bound glutamine residues and either lysine residues or mono- and poly-amines. In addition, it may act also as a G protein in transmembrane signalling, as a kinase, as a protein disulphide isomerase and as a cell surface adhesion mediator. The vast array of biochemical functions exerted by TG2 characterises and distinguishes it from all the other members of the transglutaminase family. Multiple lines of evidence suggest an involvement of the enzyme in neurodegenerative diseases, such as Huntington's (HD) and Parkinson (PD), and that its inhibition, either via drug treatments or genetic approaches, might be beneficial for the treatment of these syndromes. This review will exploit the recent developments in the comprehension of the role played by type 2 transglutaminase in eukaryotic cells, focusing on the role exerted by TG2 on mitochondrial physiology and on the regulation of cell death pathways at the basis of neurodegenerative diseases.     

Optimal treatment of leptospirosis: queries and projections

Although the global burden of leptospirosis remains enormous and new aspects of the disease are constantly recognised, little progress has been achieved in the field of leptospirosis therapeutics and queries regarding the utility of antibiotics in the late severe form of the disease remain. From the currently existing data, conclusions on the efficacy of antibiotic administration in severe or late disease cannot easily be drawn, since clinical trials have different selection criteria and may focus on Leptospira serovars with different virulence. However, as a rule the benefit of the doubt should apply. Moreover, new options, such as ceftriaxone, have a superior safety profile to penicillin. In vitro studies have outlined potential antimicrobial candidates such as macrolides and ketolides. Development of a globally accepted subunit vaccine for humans is warranted but is not expected in the near future.     

Drugs and brain mitochondrial enzymatic activities during post-natal development in rat.

The enzymatic activities of two mitochondrial enzymes, i.e. succinate dehydrogenase and NADH-cytochrome c reductase were investigated in the brain of rats at different stages of post-natal development. In addition, the effect of the pharmacological treatment with two drugs, nicergoline and bamethan, able to interact with the alpha or the beta receptors respectively, was evaluated. The results show that both the enzymatic activities rapidly increase in the first days of extra-uterine life, thus indicating an adaptation of mitochondrial oxidative processes to post-natal environmental conditions. The pharmacological treatment with the two drugs does not induce any changes in the enzymatic activities tested.     

线粒体靶向给药系统用于线粒体疾病治疗的研究进展

线粒体是细胞内具有一定结构和功能特性的细胞器,线粒体功能失调将导致机体疾病的发生,它在调节细胞凋亡方面也发挥着重要作用。为了修复线粒体功能的损伤,研究线粒体靶向给药系统显得尤为重要。本文对国内外的研究情况做简要综述。     

Recent advances in mitochondrial diseases: From molecular insights to therapeutic perspectives

Mitochondria are double-membraned cytoplasmic organelles that are responsible for the production of energy in eukaryotic cells. The process is completed through oxidative phosphorylation (OXPHOS) by the respiratory chain (RC) in mitochondria. Thousands of mitochondria may be present in each cell, depending on the function of that cell. Primary mitochondria disorder (PMD) is a clinically heterogeneous disease associated with germline mutations in mitochondrial DNA (mtDNA) and/or nuclear DNA (nDNA) genes, and impairs mitochondrial structure and function. Mitochondrial dysfunction can be detected in early childhood and may be severe, progressive and often multi-systemic, involving a wide range of organs. Understanding epigenetic factors and pathways mutations can help pave the way for developing an effective cure. However, the lack of information about the disease (including age of onset, symptoms, clinical phenotype, morbidity and mortality), the limits of current preclinical models and the wide range of phenotypic presentations hamper the development of effective medicines. Although new therapeutic approaches have been introduced with encouraging preclinical and clinical outcomes, there is no definitive cure for PMD. This review highlights recent advances, particularly in children, in terms of etiology, pathophysiology, clinical diagnosis, molecular pathways and epigenetic alterations. Current therapeutic approaches, future advances and proposed new therapeutic plans will also be discussed.     

线粒体功能障碍在心血管疾病中作用机制的研究进展

摘要：线粒体是细胞的能量代谢中心,其通过氧化磷酸化产生能量以满足心脏的高能量需求。心脏许多重要的 生理活动,如心肌收缩和细胞内稳态的维持均需要线粒体产生的三磷酸腺苷（ATP）。因此,完整的线粒体结构和功 能是心脏进行正常生理活动的前提和基础。以呼吸链功能异常和ATP合成障碍为特征的线粒体功能障碍是许多心 血管疾病的发病原因。因此,在疾病早期进行线粒体质量控制、减少线粒体功能障碍和氧化应激成为心血管疾病治 疗的新靶标。本文对线粒体功能障碍在心血管疾病中的作用机制以及相关的新型治疗策略展开综述。