The purinergic system in allotransplantation

The purine nucleotide adenosine triphosphate (ATP) is a universal source of energy for any intracellular reaction. Under specific physiological or pathological conditions, ATP can be released into extracellular spaces, where it binds and activates the purinergic receptors system (i.e. P2X, P2Y and P1 receptors). Extracellular ATP (eATP) binds to P2X or P2Y receptors in immune cells, where it mediates proliferation, chemotaxis, cytokine release, antigen presentation and cytotoxicity. eATP is then hydrolyzed by ectonucleotidases into adenosine diphosphate (ADP), which activates P2Y receptors. Ectonucleotidases also hydrolyze ADP to adenosine monophosphate and adenosine, which binds P1 receptors. In contrast to P2X and P2Y receptors, P1 receptors exert mainly an inhibitory effect on the immune response. In transplantation, a prominent role has been demonstrated for the eATP/P2X7R axis; the targeting of this pathway in fact is associated with long-term graft function and reduced graft versus host disease severity in murine models. Novel P2X receptor inhibitors are available for clinical use and are under assessment as immunomodulatory agents. In this review, we will focus on the relevance of the purinergic system and on the potential benefits of targeting this system in allograft rejection and tolerance.

Laser capture microdissection as a new tool to assess graft-infiltrating lymphocytes gene profile in islet transplantation

Innovative tolerogenic protocols in transplantation would take advantage of the development of new tools capable of evaluating the impact of these treatments on the immune system. These assays have potential for clinical application. Currently, many of these studies are based on the analysis of peripheral lymph nodes and blood-derived cells, where the percentage of alloantigen-specific cells can be low or even unpredictable. We combined a laser capture microdissection (LCM) technique with real-time PCR (RT-PCR) to evaluate gene profile of islet-infiltrating lymphocytes. Donor Lewis rats islets were transplanted under the kidney capsule in diabetic Brown Norway rats. Administration of anti-LFA1 mAb or anti-CD28 F(Ab)' was able to prolong islet survival, while the combined treatment resulted in indefinite survival. The analysis of gene expression profile for IL-2, IFN-gamma, and IL-10 production of graft-infiltrating cells revealed high IL-2, IFN-gamma, and IL-10 in untreated rats; on the contrary, the combined treatment selectively abrogated IL-2- and IFN-gamma-producing cells infiltrate. The comparison between cytokine profile in periphery (even during an allogenic extra stimulus) and in the graft revealed the dichotomy between graft and peripheral cytokine assessment. We thus propose that direct analysis of graft-infiltrating cells should be used whenever possible to evaluate the effects of a new immunomodulatory protocol.

The mitochondrial superoxide dismutase A16V polymorphism in the cardiomyopathy associated with hereditary haemochromatosis

The A16V mitochondrial targeting sequence polymorphism influences the antioxidant activity of MnSOD, an enzyme involved in neutralising iron induced oxidative stress. Patients with hereditary haemochromatosis develop parenchymal iron overload, which may lead to cirrhosis, diabetes, hypogonadism, and heart disease. The objective of this study was to determine in patients with haemochromatosis whether the presence of the Val MnSOD allele, associated with reduced enzymatic activity, affects tissue damage, and in particular heart disease, as MnSOD knockout mice develop lethal cardiomyopathy. We studied 217 consecutive unrelated probands with haemochromatosis, and 212 healthy controls. MnSOD polymorphism was evaluated by restriction analysis. The frequency distribution of the polymorphism did not differ between patients and controls. Patients carrying the Val allele had higher prevalence of cardiomyopathy (A/A 4%, A/V 11%, V/V 30%, p = 0.0006) but not of cirrhosis, diabetes, or hypogonadism, independently of age, sex, alcohol misuse, diabetes, and iron overload (odds ratio 10.1 for V/V, p = 0.006). The frequency of the Val allele was higher in patients with cardiomyopathy (0.67 v 0.45, p = 0.003). The association was significant in both C282Y+/+ (p = 0.02), and in non-C282Y+/+ patients (p = 0.003), and for both dilated (p = 0.01) and non-dilated stage (p = 0.04) cardiomyopathy, but not for ischaemic heart disease. In patients with hereditary haemochromatosis, the MnSOD genotype affects the risk of cardiomyopathy related to iron overload and possibly to other known and unknown risk factors and could represent an iron toxicity modifier gene.

The mitochondrial superoxide dismutase A16V polymorphism in the cardiomyopathy associated with hereditary haemochromatosis

The A16V mitochondrial targeting sequence polymorphism influences the antioxidant activity of MnSOD, an enzyme involved in neutralising iron induced oxidative stress. Patients with hereditary haemochromatosis develop parenchymal iron overload, which may lead to cirrhosis, diabetes, hypogonadism, and heart disease. The objective of this study was to determine in patients with haemochromatosis whether the presence of the Val MnSOD allele, associated with reduced enzymatic activity, affects tissue damage, and in particular heart disease, as MnSOD knockout mice develop lethal cardiomyopathy. We studied 217 consecutive unrelated probands with haemochromatosis, and 212 healthy controls. MnSOD polymorphism was evaluated by restriction analysis. The frequency distribution of the polymorphism did not differ between patients and controls. Patients carrying the Val allele had higher prevalence of cardiomyopathy (A/A 4%, A/V 11%, V/V 30%, p = 0.0006) but not of cirrhosis, diabetes, or hypogonadism, independently of age, sex, alcohol misuse, diabetes, and iron overload (odds ratio 10.1 for V/V, p = 0.006). The frequency of the Val allele was higher in patients with cardiomyopathy (0.67 v 0.45, p = 0.003). The association was significant in both C282Y+/+ (p = 0.02), and in non-C282Y+/+ patients (p = 0.003), and for both dilated (p = 0.01) and non-dilated stage (p = 0.04) cardiomyopathy, but not for ischaemic heart disease. In patients with hereditary haemochromatosis, the MnSOD genotype affects the risk of cardiomyopathy related to iron overload and possibly to other known and unknown risk factors and could represent an iron toxicity modifier gene.

Haemochromatosis in patients with beta-thalassaemia trait

Severe iron overload has been reported in patients with the beta-thalassaemia trait. Studies performed before the discovery of the haemochromatosis gene (HFE) have yielded conflicting results: some suggest that iron overload might arise from the interaction of the beta-thalassaemia trait with heterozygosity for haemochromatosis, some with homozygosity for haemochromatosis and others that it was unrelated to haemochromatosis. We have studied the clinical phenotype, iron indices and HFE genotypes of 22 unrelated patients with the beta-thalassaemia trait and haemochromatosis, the inheritance of chromosome 6p and 1q haplotypes in families of non-homozygous C282Y probands and serum measures of iron status in relatives heterozygous for C282Y with or without the beta-thalassaemia trait. We demonstrate that the beta-thalassaemia trait aggravates the clinical picture of C282Y homozygotes, favouring higher rates of iron accumulation and the development of severe iron-related complications. We suggest that the coexistence of the beta-thalassaemia trait might also increase the risk of iron overload in patients with HFE genotypes at a mild risk of haemochromatosis. Our findings do not support the hypothesis that the association of the beta-thalassaemia trait with a single C282Y or H63D allele might lead to iron overload and suggest that other non-HFE-related inherited factors are present in haemochromatosis patients with incomplete HFE genotypes.

Radial artery wall alterations in genetic hemochromatosis before and after iron depletion therapy

Iron overload is believed to have an adverse influence on the cardiovascular system and animal studies have shown that iron may be involved in the events that lead to atherosclerosis via an enhancement of smooth muscle cell proliferation, lipid oxidation, and free radical production. There are no data on the effect of iron overload on arterial structural and mechanical properties in humans. We measured wall thickness and distensibility (D) by ultrasonography of the radial artery in 12 patients with uncomplicated genetic hemochromatosis (GH) who were normotensive and without atherosclerotic plaques. Twelve age- and sex-matched patients were taken as controls. Nine patients were evaluated also after iron depletion. Wall thickness was greater in patients with GH than in controls (+50%, P <.01) whereas D was slightly reduced in the former group compared with the latter group, though the difference was not statistically significant. After iron depletion, a significant reduction of wall thickness and a significant increase in D were observed (-24% and +33%, P <.05 for both). Thus, in patients with hemochromatosis, arterial wall thickness is increased before the onset of cardiovascular complications. This alteration is reverted by iron depletion, which also can improve the initial and modest radial artery wall stiffening associated with this condition. Thus, functional and structural alterations in midsize muscle arteries may be an early abnormality of hemochromatosis.

Two novel nonsense mutations of HFE gene in five unrelated italian patients with hemochromatosis

BACKGROUND & AIMS

Most hemochromatosis patients of Northern European descent are homozygous for the C282Y mutation of HFE gene. In Italy, many patients with iron overload are not homozygous for C282Y, and the presence of other mutations or other genetic determinant has been suggested.

METHODS

Five unrelated Italian patients heterozygous for C282Y with the classic hemochromatosis phenotype were studied. The entire coding sequence and the exon-intron boundaries of the HFE gene were analyzed. Chromosome 6p haplotypes were defined in each patient by analysis of D6S265, D6S105, and D6S1281 microsatellites.

RESULTS

Two novel nonsense HFE mutations were identified in exon 3 in the C282Y negative chromosome. The first one, a G-to-T transition at codon 168, was detected in 3 probands; the second, a G-to-A transition at codon 169, was detected in the others.

CONCLUSIONS

The 2 nonsense mutations in the compound heterozygous state with C282Y result in the classic hemochromatosis phenotype in several unrelated Italian patients. This confirms that hemochromatosis in Italy is not as homogeneous as in northern Europe and suggests that other mutations can exist in C282Y or H63D heterozygotes with iron overload. These findings have practical implications for diagnostic and screening strategies for hemochromatosis.

Semiquantitative and qualitative assessment of hepatic iron in patients with chronic viral hepatitis: relation with grading, staging and haemochromatosis mutations

BACKGROUND

Hepatic iron overload is a common but still poorly characterized finding in patients with chronic viral hepatitis.

AIM

To evaluate lobular and cellular distribution of iron in patients with chronic viral hepatitis, the relation between hepatic iron distribution, grading and staging, and the frequency of haemochromatosis gene mutations.

PATIENTS

Thirty-four patients with chronic viral hepatitis and iron overload; 34 matched chronic viral hepatitis controls without iron overload; 139 healthy controls.

METHODS

Hepatic iron was assessed by hepatic iron concentration and Deugnier's score, histological grading and staging by Ishak's score, and frequency of haemochromatosis gene mutations by polymerase chain reaction-restriction assays.

RESULTS AND CONCLUSIONS

Iron deposits were found in hepatocytes (94% of the patients), sinusoidal tracts (88%) and portal cells (59%). In 41%, iron deposits were homogeneously distributed in the hepatic specimen. Hepatocytic iron showed a decreasing gradient from Rappaport's zone 1 to 3. Heavy alcohol intake influenced the distribution rather than the amount of hepatic iron by increasing sinusoidal iron. Haemochromatosis gene mutations were more frequent in chronic viral hepatitis patients with iron overload than in those without iron overload and in healthy controls suggesting they contribute to pathogenesis of hepatic iron accumulation. The correlation between hepatic fibrosis and portal iron supports the fibrogenetic role of iron in chronic viral hepatitis.

Hepatic iron overload in patients with chronic viral hepatitis: role of HFE gene mutations

Mild to moderate hepatic iron overload is frequent in patients with chronic viral hepatitis (CH). We evaluated the role of hemochromatosis (HFE) gene mutations and other acquired factors in the development of iron overload in these patients. We studied 110 patients with chronic B or C viral hepatitis (31 women, 79 men), including 20 with cirrhosis, and 139 controls. Hepatic iron was evaluated by semiquantitative analysis in all the patients, and hepatic iron concentration (HIC) was determined in 97 of them (26 women, 71 men). C282Y and H63D mutations were sought in all the subjects by a polymerase chain reaction-restriction assay. The frequency of HFE genotypes and alleles did not differ in patients and controls. No relation was detected between hepatic iron stores and HFE gene mutations in women. In men, all C282Y heterozygotes had iron overload, and the H63D mutation was significantly more frequent in patients with more marked hepatic siderosis than in those with mild or no siderosis (P = .0039) and in controls (P = .0008). Heavy alcohol intake and hepatic cirrhosis were also associated with increased hepatic iron stores in the men. In the 71 men in whom HIC was measured, multiple regression analysis showed that this variable was related independently only to alcohol intake and HFE gene mutations. We suggest that in patients with CH, iron accumulates in the liver as the result of an interplay between genetic and acquired factors, and that increased liver iron stores may influence progression toward liver fibrosis.

Heterogeneity of hemochromatosis in Italy

BACKGROUND & AIMS

Patients with hemochromatosis show variable phenotype expression. We evaluated the frequency of hemochromatosis gene (HFE) mutations and the contribution of HFE genotype, ancestral haplotype, ethnic background, and additional factors (alcohol intake, hepatitis viruses, and beta-thalassemia trait) to the severity of iron overload in a large series of Italian patients with a hemochromatosis phenotype.

METHODS

HFE genotype was studied in 188 patients. Phenotype evaluation was available in 153 men and 20 women and was based mainly on iron removed. HFE genotype was determined by a polymerase chain reaction restriction assay and ancestral haplotype through D6S265 and D6S105 microsatellite analysis.

RESULTS

The frequency of C282Y homozygotes was 64%, with a decreasing gradient from north to south. C282Y homozygotes showed more severe iron overload than the other HFE genotypes. In the same group, ancestral haplotype was associated with a more severe phenotype. Additional factors may favor the development of a relatively mild hemochromatosis phenotype in patients nonhomozygous for the C282Y mutation.

CONCLUSIONS

Hemochromatosis in Italy is a nonhomogenous disorder in which genetic and acquired factors are involved. In patients with a single or no HFE mutation, further studies will enable a differentiation between true genetic disorders and interactions between genetic and acquired factors.

High prevalence of the His63Asp HFE mutation in Italian patients with porphyria cutanea tarda

Sporadic porphyria cutanea tarda (PCT) is caused by a reduced activity of uroporphyrinogen decarboxylase (URO-D) in the liver. Mild to moderate iron overload is common in PCT, as iron is one of the factors which trigger the clinical manifestations of the disease through the inactivation of URO-D. A role for genetic hemochromatosis in the development of iron overload in sporadic PCT has been hypothesized in the past. The aim of this work was to investigate whether mutations of HFE, which is a candidate gene for hemochromatosis, play the role of genetic susceptibility factors for PCT in Italian patients, who have a high prevalence of acquired triggering factors, such as hepatitis C virus (HCV) chronic infection and alcohol. We determined HFE genotypes of 68 male patients with PCT. Our data do not confirm an association of PCT with the Cys282Tyr HFE mutation, strongly associated with hemochromatosis in Northern European countries. A second mutation of HFE, His63Asp, however, had a significantly increased frequency as it was present in half of the patients. Surprisingly, the presence of the His63Asp mutation was not related to the iron status of patients, suggesting that a subtle abnormality of iron metabolism induced by this mutation could escape detection by the standard parameters of iron status. In PCT patients with liver disease, the presence of the mutation could contribute to the inactivation of URO-D, either directly or through a synergistic action with other factors that cause liver damage.

Electrophysiological and MRI evaluation of neurological involvement in Behçet's disease

Eight patients with stable Behçet's disease were studied by means of multimodality evoked potentials and magnetic resonance imaging to evaluate the possibility of an earlier and objective demonstration of clinical and subclinical Central Nervous System (CNS) involvement. It was shown that both diagnostic techniques are useful for quantitative evaluation of neurological involvement in Behçet's disease; of particular interest was the demonstration of subclinical CNS changes.