A putative gene located at the MHC class I region around the D6S105 marker contributes to the setting of CD8+ T-lymphocyte numbers in humans

Higher iron stores and the HFE 187C>G variant delay onset of peripheral neuropathy during combination antiretroviral therapy

OBJECTIVE

People with HIV (PWH) continue to experience sensory neuropathy and neuropathic pain in the combination antiretroviral therapy (cART) era for unclear reasons. This study evaluated the role of iron in a previously reported association of iron-loading hemochromatosis (HFE) gene variants with reduced risk of neuropathy in PWH who received more neurotoxic cART, since an iron-related mechanism also might be relevant to neuropathic symptoms in PWH living in low-resource settings today.

DESIGN

This time-to-event analysis addressed the impact of systemic iron levels on the rapidity of neuropathy onset in PWH who initiated cART.

METHODS

Soluble transferrin receptor (sTFR), the sTFR-ferritin index of iron stores, and high-sensitivity C-reactive protein (hsCRP) levels were determined in stored baseline sera from participants of known HFE genotype from AIDS Clinical Trials Group (ACTG) Study 384, a multicenter randomized clinical trial that evaluated cART strategies. Associations with incident neuropathy were evaluated in proportional-hazards, time-to-event regression models, adjusting for potential confounders.

RESULTS

Of 151 eligible participants with stored serum who were included in the original genetic study, 43 had cART-associated neuropathy; 108 had sufficient serum for analysis, including 30 neuropathy cases. Carriers of HFE variants had higher systemic iron (lower sTFR and sTFR-ferritin index) and lower hsCRP levels than non-carriers (all p<0.05). Higher sTFR or iron stores, the HFE 187C>G variant, and lower baseline hsCRP were associated with significantly delayed neuropathy in self-reported whites (n = 28; all p-values<0.05), independent of age, CD4+ T-cell count, plasma HIV RNA, and cART regimen.

CONCLUSIONS

Higher iron stores, the HFE 187C>G variant, and lower hsCRP predicted delayed onset of neuropathy among self-reported white individuals initating cART. These findings require confirmation but may have implications for cART in HIV+ populations in areas with high endemic iron deficiency, especially those PWH in whom older, more neurotoxic antiretroviral drugs are occasionally still used.

The Herbal Bitter Drug Gentiana lutea Modulates Lipid Synthesis in Human Keratinocytes In Vitro and In Vivo

Gentiana lutea is a herbal bitter drug that is used to enhance gastrointestinal motility and secretion. Recently we have shown that amarogentin, a characteristic bitter compound of Gentiana lutea extract (GE), binds to the bitter taste receptors TAS2R1 and TAS2R38 in human keratinocytes, and stimulates the synthesis of epidermal barrier proteins. Here, we wondered if GE also modulates lipid synthesis in human keratinocytes. To address this issue, human primary keratinocytes were incubated for 6 days with GE. Nile Red labeling revealed that GE significantly increased lipid synthesis in keratinocytes. Similarly, gas chromatography with flame ionization detector indicated that GE increases the amount of triglycerides in keratinocytes. GE induced the expression of epidermal ceramide synthase 3, but not sphingomyelinase. Lipid synthesis, as well as ceramide synthase 3 expression, could be specifically blocked by inhibitors of the p38 MAPK and PPARγ signaling pathway. To assess if GE also modulates lipid synthesis in vivo, we performed a proof of concept half side comparison on the volar forearms of 33 volunteers. In comparison to placebo, GE significantly increased the lipid content of the treated skin areas, as measured with a sebumeter. Thus, GE enhances lipid synthesis in human keratinocytes that is essential for building an intact epidermal barrier. Therefore, GE might be used to improve skin disorders with an impaired epidermal barrier, e.g., very dry skin and atopic eczema.

Alzheimer's disease and HLA-A2: linking neurodegenerative to immune processes through an in silico approach

There is a controversial relationship between HLA-A2 and Alzheimer's disease (AD). It has been suggested a modifier effect on the risk that depends on genetic loadings. Thus, the aims of this study were to evaluate this relationship and to reveal genes associated with both concepts the HLA-A gene and AD. Consequently, we did first a classical systematic review and a meta-analysis of case-control studies. Next, by means of an in silico approach, we used experimental knowledge of protein-protein interactions to evaluate the top ranked genes shared by both concepts, previously found through text mining. The meta-analysis did not show a significant pooled OR (1.11, 95% CI: 0.98 to 1.24 in Caucasians), in spite of the fact that four of the included studies had a significant OR > 1 and none of them a significant OR < 1. In contrast, the in silico approach retrieved nonrandomly shared genes by both concepts (P = 0.02), which additionally encode truly interacting proteins. The network of proteins encoded by APP, ICAM-1, ITGB2, ITGAL, SELP, SELL, IL2, IL1B, CD4, and CD8A linked immune to neurodegenerative processes and highlighted the potential roles in AD pathogenesis of endothelial regulation, infectious diseases, specific antigen presentation, and HLA-A2 in maintaining synapses.

Impact of MHC class II polymorphism on blood counts of CD4+ T lymphocytes in macaque

While the number of peripheral blood T lymphocytes and of their two main subsets (CD4+CD8- and CD4-CD8+) varies little in a given healthy individual, substantial variation is observed between individuals. It was proposed that these counts could be influenced by MHC polymorphisms because of the well-established role of MHC molecules in thymic T lymphocyte maturation and presentation of antigenic peptides to peripheral T lymphocytes. To test this hypothesis, we have chosen the crab-eating macaque (Macaca fascicularis), an animal model phylogenetically close to man. We selected the Philippine macaque population because of a restriction of the MHC polymorphism in this islander population. Peripheral blood lymphocytes were counted with an automated analyzer and T lymphocyte subsets were assessed by immunolabeling and flow cytometry. The MHC polymorphism was investigated in 200 unrelated subjects using 14 microsatellites markers distributed across the MHC and the DRB locus that was genotyped by denaturing gradient gel electrophoresis and sequencing. All markers were in Hardy-Weinberg equilibrium. Allelic associations were tested with the UNPHASED software. We revealed a significant influence of the MHC class II region on CD4+ T lymphocyte blood count with the largest effect associated with a two-locus haplotypes combining the DRACA allele 274 and the DRB haplotype #8a (p < 8 × 10(-7)). Our data should stimulate a similar association study of the CD4+ T cell counts in humans.

Low numbers of CD8+ T lymphocytes in hereditary haemochromatosis are explained by a decrease of the most mature CD8+ effector memory T cells

Low CD8(+) T lymphocyte numbers have long been described in hereditary haemochromatosis (HH). Recently, two conserved haplotypes localized near the microsatellite D6S105 at the major histocompatibility complex (MHC) class I region were described predicting the clinical expression of HH and the CD8(+) T lymphocyte numbers. The A-A-T haplotype was associated with a severe clinical expression of HH and low CD8(+) T lymphocyte numbers, while the G-G-G haplotype was associated with a milder clinical expression of HH and high CD8(+) T lymphocyte numbers. As CD8(+) T lymphocytes are a very heterogeneous population, in this study we analysed the CD8(+) subpopulations of naive, central memory (T(CM)) and effector memory (T(EM)), and further subsets of CD8(+) T(EM) cells in 47 HH patients and 68 controls. In addition, association studies were conducted between the conserved haplotypes and the CD8(+) T cell subpopulations in HH. Variations of the numbers of naive and central memory cells with age were similar between HH patients and controls. For T(EM) cells and the T(EM) CD27(-)CD28(-) subset no effect of age was observed in HH [R(2) = 0.001, not significant (n.s.) and R(2) = 0.01, n.s., respectively] contrasting with the increasing of these subpopulations with age in controls (R(2) = 0.09, P = 0.017 and R(2) = 0.22, P = 0.0005, respectively). Interestingly, patients homozygous for the A-A-T haplotype have lower numbers of CD8(+) T(EM) cells due especially to lower numbers of T(EM) CD27(-)CD28(-) (0.206 +/- 0.119 and 0.066 +/- 0.067 x 10(6) cells/ml, respectively) than patients carrying the G-G-G haplotype (0.358 +/- 0.195 and 0.246 +/- 0.202 x 10(6) cells/ml, respectively). This may suggest an inability of HH patients to differentiate the CD8(+) T cells into the most mature phenotype.

A new 500 kb haplotype associated with high CD8+ T-lymphocyte numbers predicts a less severe expression of hereditary hemochromatosis

Background

Hereditary Hemochromatosis(HH) is a common genetic disorder of iron overload where the large majority of patients are homozygous for one ancestral mutation in the HFE gene. In spite of this remarkable genetic homogeneity, the condition is clinically heterogeneous, varying from a severe disease to an asymptomatic phenotype with only abnormal biochemical parameters. The recent recognition of the variable penetrance of the HH mutation in different large population studies demands the need to search for new modifiers of its phenotypic expression. The present study follows previous observations that MHC class-I linked genetic markers, associated with the setting of CD8+ T-lymphocyte numbers, could be clinically relevant modifiers of the phenotypic expression in HH, and aimed to find new markers that could be used as more reliable prognostic variables.

Methods

Haplotype analysis, including seven genetic markers within a 1 Mb region around the microsatellite D6S105 was performed in a group of 56 previously characterized C282Y homozygous Portuguese patients. Parameters analyzed in this study were total body iron stores, clinical manifestations related with HH and immunological parameters (total lymphocyte numbers, CD4+ and CD8+ T-lymphocyte numbers). An independent group of 10 C282Y homozygous patients from Vancouver, Canada, were also included in this study and analyzed for the same parameters.

Results

A highly conserved ancestral haplotype defined by the SNP markers PGBD1-A, ZNF193-A, ZNF165-T (designated as A-A-T) was found associated with both abnormally low CD8+ T-lymphocyte numbers and the development of a severe clinical expression of HH. In a small proportion of patients, another conserved haplotype defined by the SNP markers PGBD1-G, ZNF193-G, ZNF165-G (designated as G-G-G) was found associated with high CD8+ T-lymphocyte numbers and a milder clinical expression. Remarkably, the two conserved haplotypes defined in Portuguese patients were also observed in the geographically different population of Canadian patients, also predicting CD8+ T-lymphocyte numbers and the severity of disease.

Conclusion

These results may have important implications not only for approaching the question of the penetrance of the hemochromatosis gene in different world populations but also to further narrow the region of interest to find a candidate gene involved in the setting of CD8+ T-lymphocyte numbers in humans.