Association of a myeloperoxidase promoter polymorphism with multiple sclerosis

The Roles of Neutrophil-Derived Myeloperoxidase (MPO) in Diseases: The New Progress

Myeloperoxidase (MPO) is a heme-containing peroxidase, mainly expressed in neutrophils and, to a lesser extent, in monocytes. MPO is known to have a broad bactericidal ability via catalyzing the reaction of Cl- with H2O2 to produce a strong oxidant, hypochlorous acid (HOCl). However, the overproduction of MPO-derived oxidants has drawn attention to its detrimental role, especially in diseases characterized by acute or chronic inflammation. Broadly speaking, MPO and its derived oxidants are involved in the pathological processes of diseases mainly through the oxidation of biomolecules, which promotes inflammation and oxidative stress. Meanwhile, some researchers found that MPO deficiency or using MPO inhibitors could attenuate inflammation and tissue injuries. Taken together, MPO might be a promising target for both prognostic and therapeutic interventions. Therefore, understanding the role of MPO in the progress of various diseases is of great value. This review provides a comprehensive analysis of the diverse roles of MPO in the progression of several diseases, including cardiovascular diseases (CVDs), neurodegenerative diseases, cancers, renal diseases, and lung diseases (including COVID-19). This information serves as a valuable reference for subsequent mechanistic research and drug development.

Case report: Chorea and cognitive decline in a young woman: instrumental and genetic assessment of a case originally diagnosed as multiple sclerosis

We describe the case of a young woman affected by debilitating chorea and rapidly progressive cognitive decline. While her original diagnosis was multiple sclerosis, we performed a full instrumental and genetic assessement, though which we identified multiple genetic variants, including a novel variant of the APP gene. We propose some possible mechanisms by which such variants may contribute to neuroinflammation and ultimately lead to this devastating clinical course.

Non-Canonical Functions of Myeloperoxidase in Immune Regulation, Tissue Inflammation and Cancer

Myeloperoxidase (MPO) is one of the most abundantly expressed proteins in neutrophils. It serves as a critical component of the antimicrobial defense system, facilitating microbial killing via generation of reactive oxygen species (ROS). Interestingly, emerging evidence indicates that in addition to the well-recognized canonical antimicrobial function of MPO, it can directly or indirectly impact immune cells and tissue responses in homeostatic and disease states. Here, we highlight the emerging non-canonical functions of MPO, including its impact on neutrophil longevity, activation and trafficking in inflammation, its interactions with other immune cells, and how these interactions shape disease outcomes. We further discuss MPO interactions with barrier forming endothelial and epithelial cells, specialized cells of the central nervous system (CNS) and its involvement in cancer progression. Such diverse function and the MPO association with numerous inflammatory disorders make it an attractive target for therapies aimed at resolving inflammation and limiting inflammation-associated tissue damage. However, while considering MPO inhibition as a potential therapy, one must account for the diverse impact of MPO activity on various cellular compartments both in health and disease.

A novel near-infrared fluorescent probe for rapid sensing of HClO in living cells and zebrafish

Reactive oxygen species (ROS) are significant active species in living organisms, and their coordination maintains the function of organelles to resist the invasion of foreign substances. Hypochlorous acid (HClO) is not only an eventful signaling species but also a kind of ROS, which plays an irreplaceable role in the immune system. However, its abnormal levels can cause cell damage or even apoptosis, which in turn leads to the onset of a series of diseases such as inflammation, neurological diseases, and even cancer. Based on this, we designed a near-infrared fluorescent probe with a large Stokes shift for ultrafast response to HClO. Furthermore, the probe exhibits excellent sensitivity and selectivity toward HClO over other species. The probe was successfully applied to visualize endogenous and exogenous HClO in living cells and in zebrafish. This unique study is the key to providing a trustworthy tool for imaging based on the in vitro and in vivo imaging of endogenous HClO, which possesses great potential for the use in future studies of HClO-related biology and pathology.

Genetics in aphasia recovery

Considerable research efforts have been exerted toward understanding the mechanisms underlying recovery in aphasia. However, predictive models of spontaneous and treatment-induced recovery remain imprecise. Some of the hitherto unexplained variability in recovery may be accounted for with genetic data. A few studies have examined the effects of the BDNF val66met polymorphism on aphasia recovery, yielding mixed results. Advances in the study of stroke genetics and genetics of stroke recovery, including identification of several susceptibility genes through candidate-gene or genome-wide association studies, may have implications for the recovery of language function. The current chapter discusses both the direct and indirect evidence for a genetic basis of aphasia recovery, the implications of recent findings within the field, and potential future directions to advance understanding of the genetics-recovery associations.

Myeloperoxidase: A new player in autoimmunity

Myeloperoxidase (MPO) is the most toxic enzyme found in the azurophilic granules of neutrophils. MPO utilizes H2O2 to generate hypochlorous acid (HClO) and other reactive moieties, which kill pathogens during infections. In contrast, in the setting of sterile inflammation, MPO and MPO-derived oxidants are thought to be pathogenic, promoting inflammation and causing tissue damage. In contrast, evidence also exists that MPO can limit the extent of immune responses. Elevated MPO levels and activity are observed in a number of autoimmune diseases including in the central nervous system (CNS) of multiple sclerosis (MS) and the joints of rheumatoid arthritis (RA) patients. A pathogenic role for MPO in driving autoimmune inflammation was demonstrated using mouse models. Mechanisms whereby MPO is thought to contribute to disease pathogenesis include tuning of adaptive immune responses and/or the induction of vascular permeability.

Association of apolipoprotein E and myeloperoxidase genotypes to clinical course of familial and sporadic multiple sclerosis

The importance of apolipoprotein E (ApoE) and myeloperoxidase (MPO) genotypes in the clinical characteristics of multiple sclerosis (MS) has been recently emphasized. In a large group of Polish patients we have tested the hypothesis that polymorphism in ApoE and MPO genes may influence the course of the disease. G enotypes were determined in 117 MS patients (74 females and 43 males; 99 sporadic and 18 familial cases) with mean EDSS of 3.6, mean age of 44.1 years, mean duration of the disease 12.8 years and mean onset of MS at 31.2 years, and in 100 healthy controls. The relationship between ApoE and MPO genes’ polymorphism and the MS activity as well as the defect of remyelination (diffuse demyelination) and brain atrophy on MRI were analysed. The ApoE o4 allele was not related to the disease course or the ApoE o2 to the intensity of demyelination on MRI. The genotype MPO G/G was found in all familial MS and in 57% (56/99) of sporadic cases. This genotype was also related to more pronounced brain atrophy on MRI. The MPO G/G subpopulation was characterized by a significantly higher proportion of patients with secondary progressive MS (PB- 0.05) and by a higher value of EDSS. A ccording to our results the MPO G allele is frequently found (in 96% of cases) among Polish patients with MS. More severe nervous tissue damage in the MPO G/G form can be explained by the mechanism of accelerated oxidative stress. It seems that MPO G/G genotype may be one of the genetic factors influencing the progression rate of disability in MS patients.

Functional polymorphism of the myeloperoxidase gene (G-463A) in depressive patients

Gałecki P, Florkowski A, Bobińska K, Śmigielski J, Bieńkiewicz M, Szemraj J. Functional polymorphism of the myeloperoxidase gene (G-463A) in depressive patients.

OBJECTIVE

Myeloperoxidase (MPO) is an enzyme involved in the production of hypochloric acid as well as other reactive oxygen species. This enzyme plays a significant role in inflammatory processes. In view of the observed associations between depression and such inflammatory processes, as well as of the reports that confirm the presence of oxidative stress in depression, this study was designed to assess the correlation, if any, between the single nucleotide polymorphism G-463A of the MPO gene and the risk of recurrent depressive disorders (DD).

METHODS

The study was carried out in a group of 149 patients with recurrent DD and 149 healthy control subjects. Genotyping was performed by PCR/restriction fragment length polymorphism.

RESULTS

A comparison between healthy controls and depressive patients showed a statistically significant difference in genotype distribution and allele frequency in the studied groups. Genotype distribution and allele frequency did not correlate with clinical variables of the patients.

CONCLUSION

The obtained results of the study allow us to draw a cautious conclusion about the role of the analysed G-463A MPO polymorphism in recurrent DD development, which, however, requires eventual confirmation in further studies.

Myeloperoxidase: molecular mechanisms of action and their relevance to human health and disease

Myeloperoxidase (MPO) is a heme-containing peroxidase abundantly expressed in neutrophils and to a lesser extent in monocytes. Enzymatically active MPO, together with hydrogen peroxide and chloride, produces the powerful oxidant hypochlorous acid and is a key contributor to the oxygen-dependent microbicidal activity of phagocytes. In addition, excessive generation of MPO-derived oxidants has been linked to tissue damage in many diseases, especially those characterized by acute or chronic inflammation. It has become increasingly clear that MPO exerts effects that are beyond its oxidative properties. These properties of MPO are, in many cases, independent of its catalytic activity and affect various processes involved in cell signaling and cell-cell interactions and are, as such, capable of modulating inflammatory responses. Given these diverse effects, an increased interest has emerged in the role of MPO and its downstream products in a wide range of inflammatory diseases. In this article, our knowledge pertaining to the biologic role of MPO and its downstream effects and mechanisms of action in health and disease is reviewed and discussed.

Genomic regulation of CTLA4 and multiple sclerosis

The cytotoxic T lymphocyte antigen 4 gene (CTLA4) is a critical regulator of T-cell activation and it is an important therapeutic target for cancer and autoimmune diseases. Here, we analyzed the genomic regulation of CTLA4 gene expression in order to identify single nucleotide polymorphisms (SNPs) that affect its expression and splicing, and to assess their association with Multiple Sclerosis (MS). We analyzed 152 healthy subjects and 146 patients with MS, of which 52 controls and 51 patients were used for gene expression analysis. We genotyped 17 SNPs in the CTLA4 gene using the SNaPshot Multiplex Kit, and in addition gene expression of the soluble (sCTLA4) and full length (flCTLA4) isoforms was quantified by real-time PCR, while protein levels of sCTLA4 were measured by ELISA. We found that the SNPs at -1577, +6230, +10242, +10717 and +12310 influence CTLA4 expression and the combination of the -1577 GG and +6230 GG genotypes provokes the strongest decrease in CTLA4 gene expression. We found that the SNP at -658 only acted as a regulatory SNP in patients with MS, suggesting the existence of epigenetic changes due to this disease. We also identified a decrease in CTLA4 gene expression levels in patients receiving chemotherapy, although no association was observed between MS and any of the polymorphisms studied. In conclusion, we have identified several SNPs in the CTLA4 gene and studied their influence on its genetic regulation. The involvement of CTLA4 in the pathogenesis of MS may be subtle and related to the functional changes in its pathway rather than predisposing genetic polymorphisms.

The genetics of clinical outcome in multiple sclerosis

Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system (CNS), the clinical course of which varies considerably between patients. Genetic complexity and interactions with as yet unknown environmental factors have hindered researchers from fully elucidating the aetiology of the disease. In addition to influencing disease susceptibility, epidemiological evidence suggests that genetic factors may affect phenotypic expression of the disease. Genes that affect clinical outcome may be more effective therapeutic targets than those which determine susceptibility. We present in this review a comprehensive survey of the genes (both MHC- and non-MHC-related) that have been investigated for their role in disease outcome in MS. Recent studies implicating the role of the genotype and epistatic interactions in the MHC in determining outcome are highlighted.

Mammalian heme peroxidases: from molecular mechanisms to health implications

A marked increase in interest has occurred over the last few years in the role that mammalian heme peroxidase enzymes, primarily myeloperoxidase, eosinophil peroxidase, and lactoperoxidase, may play in both disease prevention and human pathologies. This increased interest has been sparked by developments in our understanding of polymorphisms that control the levels of these enzymes, a greater understanding of the basic chemistry and biochemistry of the oxidants formed by these species, the development of specific biomarkers that can be used in vivo to detect damage induced by these oxidants, the detection of active forms of these peroxidases at most, if not all, sites of inflammation, and a correlation between the levels of these enzymes and a number of major human pathologies. This article reviews recent developments in our understanding of the enzymology, chemistry, biochemistry and biologic roles of mammalian peroxidases and the oxidants that they generate, the potential role of these oxidants in human disease, and the use of the levels of these enzymes in disease prognosis.

NQO1, MPO, and the risk of lung cancer: a HuGE review

The aim of this study is to summarize the available molecular epidemiologic studies of lung cancer and metabolic genes, such as NAD(P)H quinone reductase 1 (NQO1) and myeloperoxidase (MPO). NQO1 plays a dual role in the detoxification and activation of procarcinogens whereas MPO has Phase I activity by converting lipophilic carcinogens into hydrophilic forms. Variant genotypes of both NQO1 Pro187 Ser and MPO G-463A polymorphisms may be related to low enzyme activity. The Pro/Ser and Ser/Ser genotypes combined of NQO1 was significantly associated with decreased risk of lung cancer in Japanese [random effects odds ratio (OR) = 0.70, 95% confidence interval (CI) = 0.56-0.88] among whom the variant allele is common. The variant genotype of MPO was associated with decreased risk of lung cancer among Caucasians (random effects OR = 0.70, 95% CI = 0.47-1.04). Gene-environment interactions in both polymorphisms may be hampered by inaccurate categorization of tobacco exposure. Evidence on gene-gene interactions is extremely limited. As lung cancer is a multifactorial disease, an improved understanding of such interactions may help identify individuals at risk for developing lung cancer. Such a study should include larger sample size and other polymorphisms in the metabolism of tobacco-derived carcinogens and address interactions with smoking status. The effects of polymorphisms are best represented by their haplotypes. In future studies on lung cancer, the development of haplotype-based approaches will facilitate the evaluation of haplotypic effects, either for selected polymorphisms physically close to each other or for multiple genes within the same drug-metabolism pathway.

An association study of two functional promotor polymorphisms in the myeloperoxidase (MPO) gene in multiple sclerosis

Multiple sclerosis (MS) is a chronic neurological disease affecting the central nervous system (CNS). The disease is characterised by demyelination and axonal loss caused by abnormal immunological responses resulting in accumulating neurological disabilities. MS is considered a complex disease, with both genetic and environmental factors contributing to the pathogenesis. In this study, we have investigated the genetic role of the myeloperoxidase (MPO) gene encoding myeloperoxidase in MS. MPO is an enzyme found in myeloid cells which catalyses the production of hypochlorus acid, a potent microbicidal agent. It also plays an important role in inflammatory processes, where migrating neutrophiles may release active MPO and cause tissue damage. In this study, we investigated two polymorphisms located in the promotor region of the MPO gene, known to influence the expression of MPO, in a large case/control material consisting of 871 Swedish MS patients and 532 Swedish healthy controls. No association was observed with risk of MS. Multiple Sclerosis 2007; 13: 697-700. http://msj.sagepub.com

Chlorinative stress: an under appreciated mediator of neurodegeneration?

Oxidative stress has been implicated as playing a role in neurodegenerative disorders, such as ischemic stroke, Alzheimer's, Huntington's, and Parkinson's disease. Persuasive evidences have shown that microglial-mediated oxidative stress contributes significantly to cell loss and accompanying cognitive decline characteristic of the diseases. Based on the facts that (i) levels of catalytically active myeloperoxidase are elevated in diseased brains and (ii) myeloperoxidase polymorphism is associated with the risk of developing neurodegenerative disorders, HOCl as a major oxidant produced by activated phagocytes in the presence of myeloperoxidase is therefore suggested to be involved in neurodegeneration. Its association with neurodegeneration is further showed by elevated level of 3-chlorotyrosine (bio-marker of HOCl in vivo) in affected brain regions as well as HOCl scavenging ability of neuroprotectants, desferrioxamine and uric acid. In this review, we will summary the current understanding concerning the association of HOCl and neuronal cell death where production of HOCl will lead to further formation of reactive nitrogen and oxygen species. In addition, HOCl also causes tissue destruction and cellular damage leading cell death.

Upregulation of myeloperoxidase in patients with opticospinal multiple sclerosis: Positive correlation with disease severity

To clarify the role of myeloperoxidase (MPO) in multiple sclerosis (MS), we measured serum MPO levels in 86 Japanese patients with relapsing remitting MS, 47 with opticospinal MS (OSMS) and 39 with conventional MS (CMS), and 85 healthy subjects by sandwich enzyme immunoassays and analyzed relationships with clinical features. We found a significant increase in serum MPO in OSMS patients at relapse and remission, and in CMS patients at remission compared with controls. By logistic regression analysis, the clinical variable associated with high level of MPO at remission in OSMS patients (higher than the mean+/-2 S.D. of healthy controls) was only Kurtzke's Expanded Disability Status Scale (EDSS) score in blood sampling (p=0.0245); that is, a greater EDSS scores in the high MPO group, whereas in CMS none were associated. The results of our study suggest that MPO levels in remission are related with severe tissue destruction in OSMS.

Genetic variation in the myeloperoxidase gene and cognitive impairment in multiple sclerosis

There is evidence that multiple sclerosis (MS) may associated with cognitive impairment in 25 to 40% of cases. The gene encoding myeloperoxidase (MPO) is involved in molecular pathways leading to beta-amyloid deposition. We investigated a functional biallelic (G/A) polymorphism in the promoter region (-463) of the MPO gene in 465 patients affected by MS, divided into 204 cognitively normal and 261 impaired. We did not find significant differences in allele or genotype distributions between impaired and preserved MS patients. Our findings suggest that MPO polymorphism is not a risk factor for cognitive impairment in MS.

Biosynthesis, processing, and sorting of human myeloperoxidase

Exclusively synthesized by normal neutrophil and monocyte precursor cells, myeloperoxidase (MPO) functions not only in host defense by mediating efficient microbial killing but also can contribute to progressive tissue damage in chronic inflammatory states such as atherosclerosis. The biosynthetic precursor, apoproMPO, is processed slowly in the ER, undergoing cotranslational N-glycosylation, transient interactions with the molecular chaperones calreticulin and calnexin, and heme incorporation to generate enzymatically active proMPO that is competent for export into the Golgi. After exiting the Golgi the propeptide is removed prior to final proteolytic processing in azurophil granules, resulting in formation of a symmetric MPO homodimer linked by a disulfide bond. Some proMPO escapes granule targeting and becomes constitutively secreted to the extracellular environment. Although the precise mechanism is unknown, the pro-segment is required for normal processing and targeting, as propeptide-deleted MPO precursor is either degraded or constitutively secreted. Characterizing the molecular consequences of naturally occurring mutations that cause inherited MPO deficiency provides unique insight into the structural determinants of MPO involved in biosynthesis, processing and targeting.

Polymorphisms of tumor necrosis factor and myeloperoxidase genes in patients with chronic renal failure on peritoneal dialysis

BACKGROUND

Analyzing the molecular variants of immunological system genes helps to develop our understanding of the pathogenesis of several diseases. The tumor necrosis factor (TNF) is an important cytokine of cellular response and inflammation. The TNF gene is located within the MHC region on chromosome 6p21.3. Single nucleotide polymorphisms in the TNF gene, such as the one at a position -308, probably have a direct influence on TNF production. Myeloperoxidase, a heme enzyme, participates in micro-organism killing. The myeloperoxidase (MPO) gene is located on chromosome 17. In the promoter region, at position -463, G to A transition has been found, which causes decreased gene expression.

AIM

The aim of our study was to analyze the genetic polymorphisms of the TNF and MPO genes in patients with chronic renal failure.

METHODS

The study included 95 patients with chronic renal failure and 115 healthy individuals. All participants were genotyped for TNF-308 and MPO promoter region polymorphisms by PCR, followed by digestion and gel electrophoresis. Genotype distribution was compared between patients and controls. For statistical analysis the Statistica PL 6.0 program was used. The Kruskal-Wallis and median test were employed; to evaluate relationship between quantitative data chi-square test was used.

RESULTS

There were no significant differences in genotype distribution of TNF or MPO polymorphisms between patients and controls. Some differences may be associated with gender because the TNF1/TNF1 genotype was significantly more common in healthy women in comparison with women with chronic renal failure (p < 0.05). In men, no such differences were found. For MPO polymorphism, in men with renal failure the GG genotype was significantly more frequent than in healthy men (p < 0.05). Comparing the MPO genotype distribution in diabetic nephropathy patients and nondiabetic patients, we found a statistically significant difference: GG and AA genotypes were more frequent in diabetic nephropathy than in other renal diseases (73 versus 60% and 10.8 versus 1.7%, respectively; p < 0.05). The genotype distribution in patients with other renal diseases was similar to the control group. There was a correlation between the TNF genotype and the age of onset of glomerulonephritis. For myeloperoxidase, there was a significant association between genotype and the age of onset of renal disease. There was no relationship between the TNF and MPO genotypes and time to end-stage renal disease.

CONCLUSION

Our studies show that the TNF and MPO genes may play a role in chronic renal failure. The relationship observed between polymorphisms of the TNF and MPO genes and chronic renal failure may depend on the pathophysiological changes in different diseases underlying renal failure.

Myeloperoxidase G-463A polymorphism and Alzheimer's disease in the ApoEurope study

Alzheimer's disease (AD) is the most common cause of dementia in the elderly. Epidemiological and molecular genetic studies have shown the existence of several genes associated with increased risk of AD, the major genetic susceptibility locus coding for apolipoprotein E (apoE). A polymorphism in the myeloperoxidase gene (MPO) has previously been associated with AD susceptibility. However, results in the literature are controversial and seem to be dependent on several factors such as gender, apoE polymorphism or the genetic structure of the population. We investigated MPO G-463A and apoE polymorphism in 265 cases and 246 controls from the ApoEurope Study. In females, we found a significant association between MPO genotype and AD (P=0.034), GG genotype frequency being lower in cases (52.4%) as compared to controls (64.2%). In men, there was no significant effect of MPO polymorphism. No interaction was found between MPO polymorphism and apoE epsilon 4 allele. In conclusion, the G-463A polymorphism of MPO was statistically associated with AD in a gender-specific manner. However, given the low significance of P value we suggest no causal effect of the MPO gene in AD, as also evidenced in a recent meta-analysis. Our results support the hypothesis of a possible linkage disequilibrium between the MPO G-463A gene polymorphism and another functional variant involved in AD.

Myeloperoxidase polymorphisms in brain infarction. Association with infarct size and functional outcome

Myeloperoxidase (MPO) has been shown to contribute to several diseases and more particularly to atherosclerosis through excessive ROS production via the MPO/H(2)O(2)/Cl(-) oxidation system. The aim of this study was to determine whether there is an association between MPO polymorphisms and brain infarction (BI), one of the main consequences of atherosclerosis. We investigated MPO G-463A and G-129A polymorphisms in 450 patients with BI confirmed by magnetic resonance imaging (MRI) and 450 controls of the GENIC (Génétique de l'Infarctus Cérébral) Study. Genotype determination of MPO was performed by polymerase chain reaction and allele-specific oligonucleotide hybridization (ASO). Genotype distributions for each of both MPO polymorphisms were found to be similar between cases and controls overall, and according to etiologic subtypes or gender. The frequency of the A allele of the G-463A polymorphism was 22% (95% confidence interval, 19.4 to 24.9) and the frequency of the A allele of the G-129A polymorphism was 6.8% (95% confidence interval, 5.3 to 8.6). The odds ratio (OR) for BI in carriers of the A allele of the G-129A polymorphism was 0.92 (95% confidence interval, 0.61 to 1.39), and the OR for BI in carriers of the A allele of the G-463A polymorphism was 1.15 (95% confidence interval, 0.88 to 1.52). No association between the main risk factors for BI such as hypertension, cholesterol, diabetes and MPO polymorphisms was found. In analyses restricted to cases, we identified an association between the A allele of the G-129A polymorphism and the size of the brain infarct (P=0.01). Furthermore, the A allele of the G-463A polymorphism was associated with a poorer functional short-term outcome as evaluated by the Rankin score (P=0.02). In conclusion, MPO polymorphisms were associated with the extent of brain damage and the functional outcome rather than with the risk of developing a BI.

Interleukin 1 genotypes in multiple sclerosis and relationship to disease severity

We studied the association between clinical outcome in MS and allelic variants single nucleotide polymorphisms (SNPs) of interleukin-1alpha (IL-1alpha), IL-1beta and a variable number tandem repeat (VNTR) in IL-1 receptor antagonist (IL-1RN). A total of 377 patients with MS were studied. Significant associations between IL-1 genotypes and clinical outcome were found using logistic regression after correction for gender, onset age and disease duration. The same trends were subsequently demonstrated in a second independent group of 67 primary progressive patients. Our results suggest that genetically determined immunomodulation mediated by IL-1 influences long-term prognosis in multiple sclerosis (MS).

Genetics of multiple sclerosis: linkage and association studies

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system caused by an interplay of environmental and genetic factors. The only genetic region that has been clearly demonstrated by linkage and association studies to contribute to MS genetic susceptibility is the human leukocyte antigen (HLA) system. The majority of HLA population studies in MS have focused on Caucasians of Northern European descent, where the predisposition to disease has been consistently associated with the class II DRB1*1501-DQA1*0102-DQB1*0602 haplotype. A positive association with DR4 was detected in Sardinians and in other Mediterranean populations. Moreover DR1, DR7, DR11 have been found to be protective in several populations. Systematic searches aimed at identifying non-HLA susceptibility genes were undertaken in several populations by means of linkage studies with microsatellite markers distributed across the whole genome. The conclusion of these studies was that there is no major MS locus, and genetic susceptibility to the disease is most likely explained by the presence of different genes each conferring a small contribution to the overall familial aggregation. The involvement of several candidate genes was tested by association studies, utilizing either a population-based (case control) or a family-based (transmission disequilibrium test) approach. Candidate genes were selected mainly on the basis of their involvement in the autoimmune pathogenesis and include immunorelevant molecules such as cytokines, cytokine receptors, immunoglobulin, T cell receptor subunits and myelin antigens. With the notable exception of HLA, association studies met only modest success. This failure may result from the small size of the tested samples and the small number of markers considered for each gene. New tools for large scale screening are needed to identify genetic determinants with a low phenotypic effect. Large collaborative studies are planned to screen several thousands of patients with MS with several thousands of genetic markers. The tests are increasingly based on the DNA pooling procedure.

Identifying disease modifying genes in multiple sclerosis

Evidence is mounting that genetic variation influences not only susceptibility to multiple sclerosis (MS), but also its course and severity. Identification of disease modifying genes, however, poses unique challenges, especially on how to classify the course and outcome of the disease in ways that may be relevant to analysis of biological factors that might be influenced by genes. The power of the statistical approaches to detect small effects of individual genes in complex disorders such as MS is problematic, and approaches to estimate power must be appropriate for the data. Nonetheless, using contemporary schemes of classification, genetic variants that influence disease course have been found; in fact, a small number have been confirmed to influence disease course in two or more independent studies. This review addresses strategies relevant to identification of disease modifying genes in MS, and summarizes and critically evaluates the current state of knowledge in this area.

Myeloperoxidase -463 (G-->A) polymorphism associated with lower risk of lung cancer

OBJECTIVE

To study the association of the myeloperoxidase (MPO) -463 (G-->A) polymorphism with lung cancer risk.

PATIENTS AND METHODS

We performed a paired case-control analysis of 307 patients with primary lung cancer and an equal number of age-, sex-, and ethnicity-matched controls to evaluate the effect of the MPO -463 (G-->4A) polymorphism on disease susceptibility. We also performed conditional logistic regression analyses to evaluate the effect of the polymorphism adjusted for smoking status and chronic obstructive pulmonary disease, 2 established risk factors. We used 2 models for these analyses: one to compare homozygous (AA) genotypes with wild type (GG) and heterozygous (GA) genotypes and one to compare carriers (heterozygotes and AA homozygotes) with GG genotypes. Finally, we combined the results from the published studies of this putative association and performed a stratified analysis.

RESULTS

The AA genotype was inversely associated with susceptibility to lung cancer (odds ratio [OR], 0.39; 95% confidence interval [CI], 0.15-1.00). There was no association in heterozygotes. However, in the stratified analysis, we found an association between patients with the AA (OR, 0.44; 95% CI, 0.27-0.68) and GA (OR, 0.77; 95% CI, 0.64-0.93) genotypes vs the GG genotype.

CONCLUSION

Our results are consistent with previous reports and show that homozygotes of the less common A allele of MPO -463 polymorphism have a 2.6-fold lower risk of lung cancer.

Growing significance of myeloperoxidase in non-infectious diseases

Myeloperoxidase (MPO) is a glycoprotein released by activated polymorphonuclear neutrophils, which takes part in the defense of the organism through production of hypochlorous acid (HOCl), a potent oxidant. Since the discovery of MPO deficiency, initially regarded as rare and restricted to patients suffering from severe infections, MPO has attracted clinical attention. The development of new technologies allowing screening for this defect has permitted new advances in the comprehension of underlying mechanisms. Apart from its implications for host defense, the expression of MPO restricted to myeloid precursors makes MPO mRNA a good marker of acute myeloid leukemia. In addition, during the last few years, involvement of MPO has been described in numerous diseases such as atherosclerosis, lung cancer, Alzheimer's disease and multiple sclerosis. Both strong oxidative activity and MPO genetic polymorphism have been involved. This review summarizes the broad range of diseases involving MPO and points out the possible use of this protein as a new clinical marker and a future therapeutic target.

Association between Alzheimer's disease and a functional polymorphism in the Myeloperoxidase gene

A polymorphism in the Myeloperoxidase gene (MPO) has previously been demonstrated to be associated with gender-specific risk in an Alzheimer's Disease (AD) autopsy sample. We have investigated this polymorphism in our own samples of 226 Caucasian cases and 166 controls and 59 Hispanic cases and 75 controls. In Caucasians we find a significant association between MPO genotype and AD (P = 0.03), although we do not observe any effects of gender or any interaction with the APOE gene. Specifically, the MPO GG genotype contributes a 1.57-fold increased risk for AD. In Hispanics there was no effect of MPO genotype, or of MPO genotype in interaction with age or gender, on diagnosis of AD.