Current Molecular Medicine - Volume 9, Issue 3, 2009

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies that can form immune complexes and deposit in tissues, causing inflammation and organ damage. There is evidence that interferons and some interleukins can have an active role in the pathogenesis of SLE and can contribute significantly to the immune imbalance in the disease, whereas the role of some cytokines (such as TNF) is still debated. This review discusses the activity of several cytokines in SLE, their effects on the immune cells in relation to the disease pathogenesis, and the promise and limitations of cytokine- based therapies in clinical trials for lupus patients.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder of the motor neurons in the spinal cord, brainstem, and motor cortex. Ten percent of ALS cases are familial, with both autosomal dominant and recessive modes of inheritance reported. Mutations in the copper/zinc superoxidedismutase- 1 (SOD-1) gene, the first gene linked with ALS, result in the classical ALS phenotype. To date, 135 mutations have been identified in the SOD-1 gene, accounting for ∼ 20% of familial ALS cases. Mutations are widely distributed throughout the gene with preponderance for exon 4 and 5. Although mutations result in a toxic gain of function of the SOD-1 enzyme, which normally functions as a free radical scavenger, the mechanisms underlying motor neuron degeneration have not been clearly elucidated. Evidence is emerging of a complex interaction between genetic and molecular factors, with resultant damage of critical target proteins and organelles within the motor neuron. The clinical effectiveness afforded by anti-glutamatergic agents such as riluzole, suggests that glutamate excitotoxicity contributes to neurodegeneration in ALS, with glutamate excitotoxicity mediated via corticomotoneurons that provide a direct link between the motor cortex and the spinal motor neuron. This review provides an overview of the genetics of ALS, and describes recent advances in the understanding of the pathophysiological mechanisms underlying neurodegeneration.

Radiation therapy is a key component of the management of various pelvic tumors, including prostate, gynecological, and anorectal carcinomas. Unfortunately, normal tissues located in the vicinity of target organs are radiosensitive, and long-term cancer survivors may develop late treatment-related injury, most notably radiation-induced fibrosis (RIF) of the small bowel. The cellular mediators of intestinal fibrosis are mesenchymal cells (i.e. myofibroblasts, fibroblasts and smooth muscle cells) which, when activated, serve as the primary collagen-producing cells, and are responsible for excess deposition of extracellular matrix components, eventually leading to intestinal loss of function. For decades, the underlying mechanisms involved in chronic activation of myofibroblasts within the normal tissues were unknown, and the fibrotic process, which ensued, was considered irreversible. Recent advances in the pathogenesis of RIF have demonstrated prolonged upregulation of fibrogenic cytokines, such as Transforming growth factor-β1 (TGF-β1) and its main downstream effector, Connective tissue growth factor (CTGF), in the myofibroblasts of irradiated small bowel. TGF-β1-mediated activation of CTGF gene expression is controlled by Smads, but recently Rho/ROCK signaling has emerged as an alternative pathway involved in the control of CTGF expression in intestinal fibrosis. This article underlines the clinical relevance of RIF as it relates to damage to the small bowel, provides insight to its molecular biology, and finally unveils the potential role of Rho-ROCK inhibitors as emerging strategies to promote RIF reversal.

Type 2 Diabetes occurs as a result of defects in insulin secretion and its function. Although mechanisms of disease are not fully elucidated, it is recognized that a progressive decline in insulin secretory capacity is responsible for its occurrence and natural course. Metabolic syndrome, known to be a precursor of Type 2 diabetes, is characterized by a constellation of vascular risk factors, with obesity playing a central role. Obesity contributes to impaired insulin function and abnormal glucose metabolism. MicroRNAs (miRNA) are highly conserved, small, RNA molecules encoded in the genomes of plants and animals and they regulate the expression of many other genes either by RNA interference (RNAi) or RNA activation (RNAa). miRNAs have been found to regulate multiple genes and seem to be crucial factors in many cellular pathways, including development, cell differentiation, proliferation and apoptosis. Pancreatic islet cell specific miRNAs which regulate insulin secretion, and adipocyte specific miRNAs which regulate adipocyte differentiation, are examples of miRNAs that are predicted to have crucial roles in governing glucose homeostasis. Further understanding of the roles of miRNAs in glucose metabolism may unravel better understanding of pancreatic cell biology and diabetes pathophysiology, allowing for newer therapeutic targets and strategies. In this review, we will be discussing about the role/function of miRNAs in insulin secretion and regulation, lipid metabolism and conditions like hypertension and cardiovascular diseases and the potential use of miRNA in therapy.

Cardiovascular disease is one of the leading causes of morbidity and mortality around the world. Even after successful revascularization in coronary artery disease, cell death continues and the loss of cardiomyocytes eventually leads to progressive ventricular dilation and heart dysfunction. The notion of repairing or regenerating lost myocardium via cell-based therapies remains highly appealing. The recent identification of human stem cells, including embryonic stem cells and adult stem cells, has raised optimism for the development of a new therapy. This new cell-therapy and the concept of regenerative medicine is aimed at restoring the damaged myocardium, both vasculature and muscle. Here, we review the stem cell field and other available cell sources for myocardial regeneration, focusing on the up-to-date status of stem cell biology, recent laboratory advances and the current clinical applications. In addition, the limitations and practical hurdles that need urgent solution before more extensive applications become feasible are also discussed.

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of common hepatic disorders in western countries, with multiple consequences and its incidence is paralleling the increasing numbers of overweight and obese individuals worldwide. The pathogenesis of NAFLD is thought to be related mainly with insulin resistance (IR) syndrome and oxidative stress; the latter resulting from mitochondrial fatty acids (FFAs) oxidation, nuclear factor-kappaB (NFκB)-dependent inflammatory cytokine expression and adipocytokines may promote hepatocellular damage, inflammation, fibrosis and progressive liver disease. Adipocytokines and other recognized cytokines produced partially by inflammatory cells infiltrating adipose tissue, play an important role in the pathogenesis of IR and NAFLD, through complex and interactive paracrine and endocrine mechanisms. Some adipocytokines, including adiponectin and leptin decrease IR, while others, including tumor necrosis factor (TNF)-α, interleukin (IL)-6 and resistin enhance IR. The multi-hit hypothesis provides a model that summarizes the complex factors and interactions leading from adipocytokines, FFAs metabolism and IR to NAFLD. This review outlines the pathways involved in adipocytokines, IR and NAFLD sequence; the first part describes the impaired IR pathway leading to NAFLD and the second part the mechanisms by which adipocytokines influence IR and NAFLD development and progression. Understanding these complex mechanisms has evoked new therapeutic approaches, which may provide promising results to date.

Folic acid plays an important role in neuroplasticity and in the maintenance of neuronal integrity. Folate is a co-factor in one-carbon metabolism during which it promotes the regeneration of methionine from homocysteine, a highly reactive sulfur-containing amino acid. Methionine may then be converted to Sadenosylmethionine (SAM), the prinicpal methyl donor in most biosynthetic methylation reactions. On the cellular level, folate deficiency and hyperhomocysteinemia exert multiple detrimental effects. These include induction of DNA damage, uracil misincorporation into DNA and altered patterns of DNA methylation. Low folate status and elevated homocysteine increase the generation of reactive oxygen species and contribute to excitotoxicity and mitochondrial dysfunction which may lead to apoptosis. Strong epidemiological and experimental evidence links derangements of one-carbon metabolism to vascular, neurodegenerative and neuropsychiatric disease, including most prominently cerebral ischemia, Alzheimer's dementia and depression. Although firm evidence from controlled clinical trials is largely lacking, B-vitamin supplementation and homocysteine reduction may have a role especially in the primary prevention of stroke and dementia as well as as an adjunct to antidepressant pharmacotherapy.

Toll-like receptors (TLR) constitute one of the components of the innate immunity, based on the recognition of conserved molecular structures found in large groups of pathogens. A total of 11 Toll-like receptors have now been described in humans. Toll-like receptors are expressed on virtually every type of cell, including immunocompetent cells. Ligand binding triggers signaling cascade that leads to the induction of key proinflammatory mediators that contribute to an immune response. Additionally, TLR induction results in the activation and shaping of the adaptive immune reaction. TLRs have also been identified as potential therapeutic targets. Their capability to augment antigen presentation or induce the expression of target molecules has rendered them plausible therapeutic agents. Recently, synthetic ligands have been described and some of them have already been established in the treatment of skin cancer (TLR7 agonist) and as anti-hepatitis B virus vaccine adjuvants (TLR4 agonists). Furthermore, many clinical trials on TLR agonists as potent enhancers of antitumor response in solid tumors are currently on going. Considering that TLRs are widely expressed on transformed cells of the immune system (from blasts to memory cells), they may become a promising candidate for developing effective therapeutic options in hematologic malignancies as many in vitro studies have shown the intact functionality of TLRs in transformed cells. Moreover, a few clinical trials investigating the safety of synthetic TLR agonists are currently ongoing. Therefore, it is necessary to conduct further studies in order to assess the clinical relevance of the applicability of TLR-aimed therapy in the treatment of hematologic malignancies.

Cerebrovascular disease is one of the commonest causes of disability and mortality worldwide. Over the past two decades, a tremendous amount of research has been undertaken into developing effective therapeutic strategies for the treatment of acute stroke. Unfortunately, many neuroprotective agents that have shown successful results in treating animal models of acute stroke have failed to translate into clinical treatments. Only tissue-plasminogen activator (t-PA) is currently licensed for use in the treatment of acute ischaemic stroke. One of the important pathophysiological mechanisms involved during the acute phase of stroke is neuroinflammation. This review article will discuss the molecular aspects of neuroinflammation in acute ischaemic stroke and potential therapeutic strategies as part of translational medicine research.

The epidermis is the stratified epithelium that covers and protects the body from external damage. This tissue undergoes continuous cell renewal throughout the life of the individual at the expense of a pool of pluripotent cells, some of them lie in a well defined niche in the hair follicle known as the bulge. Epidermal tumours are the most frequent type of cancer in human populations, as a consequence, the development and progression of these tumours have been extensively characterised and a number of mouse models generated. Over the last years several findings suggest that a subset of cells, named cancer stem cells, could play an important role in tumour development; however, the identity of these cells remains unknown in most cases. Understanding the biology of these cells and their implication in tumour development and progression is crucial to design therapies aimed to target cancer stem cells. In this scenario, the epidermis emerges as a good model to gain deeper insight into the role of adult stem cells in carcinogenesis. Here we summarise recent findings in the field using genetically manipulated mice and how these can be translated to humans.

Toll-like receptors (TLRs) form a large family of pattern recognition receptors with at least 11 members in human and 13 in mouse. TLRs recognize a wide variety of microbial components and potential hostderived agonists that have emerged as key mediators of innate immunity. TLR signaling also plays an important role in the activation of the adaptive immune system by inducing proinflammatory cytokines and upregulating costimulatory molecules of antigen presenting cells. The dysregulation of TLR signaling may cause autoimmunity. This review discusses the contribution of TLR signaling to the initiation and progression of autoimmune diseases, such as rheumatoid arthritis, experimental autoimmune encephalitis, myocarditis, hepatitis, kidney disease, systemic lupus erythematosus, diabetes, obesity, and experimental autoimmune uveitis as well as aging. The involvement of TLR signaling in the pathogenesis of autoimmune diseases may provide novel targets for the development of therapeutics.

Mutations in humans are associated with several forms of inherited retinal dystrophies, such as Retinitis Pigmentosa which lead to retinal cell death and irreversible loss of vision. Genes involved in affected patients mainly encode proteins related to vision physiology including visual cycle and light-dependent phototransduction cascade. As reported in spontaneous and genetically engineered mouse models, apoptosis is a common fate in retinal degeneration, although the triggered signals to retinal apoptosis remain largely unraveled. Several studies highlighted that many of the molecular pathways involved in ocular diseases rely on caspase- dependent or -independent apoptotic mitochondrial pathway involving the Bcl-2 family of proteins. Antiand pro-apoptotic Bcl-2 members are present in retinal tissues and are thought to play a role in the pathogenesis of several retinal disorders. Since almost no efficient treatments are available so far, it remains a great challenge to decipher the molecular pathways involved in retinal dystrophies and to develop alternative therapies to prevent or inhibit eye defect. Toward this goal, mutation-independent strategies such as molecular therapy provides promising and exciting approaches to deliver anti-apoptotic molecules targeting the Bcl-2 pathway through the use of cell permeable transport peptides. Modulation of common apoptotic signaling pathways may be of outstanding potential to target multiple retinal dystrophies regardless of the primary genetic defect.

Asthma is an inflammatory disorder of the airways that has been typified by its bronchospastic component. New attention has been directed to the long-term changes in asthmatic airways as indicated by the accelerated rate of lung function decline occurring in these patients despite therapy with inhaled corticosteroids. These structural changes in the airway wall, termed airway remodeling, are now thought to be a key component in the pathophysiology of asthma. Airway remodeling is characterized by thickening of the lamina reticularis with deposition of collagen and other extracellular matrix proteins leading to subepithelial fibrosis and increased airway goblet cells causing mucus hypersecretion. Of note, there is myofibroblast proliferation and increased airway smooth muscle mass caused by both hyperplasia and hypertrophy of smooth muscle cells. While an important role for cysteinyl leukotrienes (CysLTs) in the pathogenesis of airway inflammation and bronchoconstriction in asthma has been well-established, the specific role of CysLTs in airway remodeling is less clear. This aim of this review is to summarize the data from mouse models of asthma as well as limited human studies that demonstrate a key role for CysLTs in allergen-induced mucus hypersecretion, thickening of the lamina reticularis, and subepithelial fibrosis in the lungs. We will also focus on the interaction between CysLTs and cytokines/growth factors that mediate these changes in epithelial cells, smooth muscle cells, vasculature, and other structural components of the lungs in patients with asthma.

p66Shc is the only known proapoptotic member of the Shc protein family of molecular adaptors. Through its redox activity, p66Shc oxidates cytochrome-c, leading to increased ROS production and, eventually, to apoptosis. p66Shc has been implicated in the control of oxidative stress and life span in mammals. In this review the multifaceted role of p66Shc in redox regulation will be discussed, with a focus on the mechanisms underlying p66Shc-dependent apoptosis and its role in oxidative stress-related diseases.