Association of Tagging Single Nucleotide Polymorphisms on 8 Candidate Genes in Dopaminergic Pathway with Schizophrenia in Croatian Population

Aim

To perform a comprehensive evaluation of association of common genetic variants in candidate genes in the dopaminergic pathway with schizophrenia in a sample from Croatian population.

Methods

A case-control association study was performed on 104 unrelated patients with schizophrenia recruited from a psychiatric hospital in Zagreb and 131 phenotypically normal Croatian subjects. Forty-nine tagging single nucleotide polymorphisms (tagSNPs) in 8 candidate genes in the dopaminergic pathway were identified from the HapMap database and tested for association. Genotyping was performed using the SNPlex platform. Statistical analysis was conducted to assess allelic and genotypic associations between cases and controls using a goodness of fit χ² test and trend test, respectively; adjustment for multiple testing was done by permutation based analysis.

Results

Significant allele frequency differences between schizophrenia cases and controls were observed at 4 tagSNPs located in the genes DRD5, HTR1B1, DBH, and TH1 (P < 0.005). A trend test also confirmed the genotypic association (P < 0.001) of these 4 tagSNPs. Additionally, moderate association (P < 0.05) was observed with 8 tagSNPs on SLC6A3, DBH, DRD4, SLC6A4, and COMT.

Conclusions

Common genetic variants in genes involved in the dopaminergic pathway are associated with schizophrenia in the populations of Caucasian descent.Schizophrenia is a chronic, severe, and disabling brain disease affecting about 1% of the global population (1). There is substantial evidence that genetic factors are involved in the etiology of the disease (2). High heritability (~ 80%) and higher concordance in monozygotic (~ 50%) than in dizygotic (~ 17%) twins are strong indicators for an inherited basis of schizophrenia (3-5). During the past decade, numerous loci and plausible candidate genes have been identified by linkage and association studies. However, the findings have remained inconclusive (2,6). Like other complex diseases, a complex genetic etiology compounded by involvement of other non-genetic factors has hindered the precise identification of schizophrenia gene variants. Second, a major limitation in most association studies has been testing of a few variants within a gene of interest rather than a thorough assessment of the entire gene region. With the availability of the sequence of the genome and large body of data on human genetic variation from the HapMap project (7), it is now possible to undertake more comprehensive association studies.Genes involved in the dopamine pathway are biologically plausible candidates in schizophrenia susceptibility. In this study, we report on the association of single nucleotide polymorphisms (SNPs) in 8 dopaminergic genes (DRD4, DRD5, SLC6A3, SLC6A4, HTR1B, DBH, TH, and COMT) with schizophrenia in a Caucasian sample from Croatia. We performed a comprehensive association study using tagging SNPs (tagSNPs). Overall, 49 tagSNPs were identified from the HapMap database (7), 4 of which showed strong evidence of association with schizophrenia susceptibility.     

Chronic hyperammonemia, glutamatergic neurotransmission and neurological alterations

This mini-review focus on our studies on alterations in glutamatergic neurotransmission and their role in neurological alterations in rat models of chronic hyperammonemia and hepatic encephalopathy (HE). Hyperammonemia impairs the glutamate-nitric oxide (NO)-cGMP pathway in cerebellum, which is responsible for reduced learning ability. We studied the underlying mechanisms and designed treatments to restore the pathway and learning. This was achieved by treatment with: phosphodiesterase 5 inhibitors, cGMP, anti-inflammatories (ibuprofen), p38 inhibitors or GABA_A receptor antagonists (bicuculline). Hyperammonemia alters signal transduction associated to metabotropic glutamate receptors (mGluRs). Hypokinesia in hyperammonemia and HE is due to increased extracellular glutamate and mGluR1 activation in substantia nigra; blocking this receptor restores motor activity. The motor responses to mGluRs activation in nucleus accumbens (NAcc) are altered in hyperammonemia and HE, with reduced dopamine and increased glutamate release. This leads to activation of different neuronal circuits and enhanced motor responses. These studies show that altered responses to activation of NMDA receptors and mGluRs play essential roles in cognitive and motor alterations in hyperammonemia and HE and provide new treatments restoring cognitive and motor function.     

Regulatory T cells interfere with the development of bronchus-associated lymphoid tissue

Presence and extent of bronchus-associated lymphoid tissue (BALT) is subject to considerable variations between species and is only occasionally observed in lungs of mice. Here we demonstrate that mice deficient for the chemokine receptor CCR7 regularly develop highly organized BALT. These structures were not present at birth but were detectable from day 5 onwards. Analyzing CCR7(-/-)/wild-type bone marrow chimeras, we demonstrate that the development of BALT is caused by alterations of the hematopoietic system in CCR7-deficient mice. These observations together with the finding that CCR7-deficient mice possess dramatically reduced numbers of regulatory T cells (T reg cells) in the lung-draining bronchial lymph node suggest that BALT formation might be caused by disabled in situ function of T reg cells. Indeed, although adoptive transfer of wild-type T reg cells to CCR7-deficient recipients resulted in a profound reduction of BALT formation, neither naive wild-type T cells nor T reg cells from CCR7(-/-) donors impair BALT generation. Furthermore, we provide evidence that CCR7-deficient T reg cells, although strongly impaired in homing to peripheral lymph nodes, are fully effective in vitro. Thus our data reveal a CCR7-dependent homing of T reg cells to peripheral lymph nodes in conjunction with a role for these cells in controlling BALT formation.     

Genetic analysis of the dihydrofolate reductase-thymidylate synthase gene from geographically diverse isolates of Plasmodium malariae

Plasmodium malariae, the parasite responsible for quartan malaria, is transmitted in most areas of malaria endemicity and is associated with significant morbidity. The sequence of the gene coding for the enzyme dihydrofolate reductase-thymidylate synthase (DHFR-TS) was obtained from field isolates of P. malariae and from the closely related simian parasite Plasmodium brasilianum. The two sequences were nearly 100% homologous, adding weight to the notion that they represent genetically distinct lines of the same species. A survey of polymorphisms of the dhfr sequences in 35 isolates of P. malariae collected from five countries in Asia and Africa revealed a low number of nonsynonymous mutations in five codons. In five of the isolates collected from southeast Asia, a nonsynonymous mutation was found at one of the three positions known to be associated with antifolate resistance in other Plasmodium species. Five isolates with the wild-type DHFR could be assayed for drug susceptibility in vitro and were found to be sensitive to pyrimethamine (mean 50% inhibitory concentration, 2.24 ng/ml [95% confidence interval, 0.4 to 3.1]).     

Hydrotherapy versus conventional land-based exercise for the management of patients with osteoarthritis of the knee: a randomized clinical trial

BACKGROUND AND PURPOSE: This study was designed to evaluate the effectiveness of hydrotherapy in subjects with osteoarthritis (OA) of the knee compared with subjects with OA of the knee who performed land-based exercises. SUBJECTS AND METHODS: Sixty-four subjects with OA of the knee were randomly assigned to 1 of 2 groups that performed exercises for 18 weeks: a water-based exercise group and a land-based exercise group. The outcome measures included a visual analog scale (VAS) for pain in the previous week, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), pain during gait assessed by a VAS at rest and immediately following a 50-foot (15.24-m) walk test (50FWT), walking time measured at fast and comfortable paces during the 50FWT, and the Lequesne Index. Measurements were recorded by a blinded investigator at baseline and at 9 and 18 weeks after initiating the intervention. RESULTS: The 2 groups were homogenous regarding all parameters at baseline. Reductions in pain and improvements in WOMAC and Lequesne index scores were similar between groups. Pain before and after the 50FWT decreased significantly over time in both groups. However, the water-based exercise group experienced a significantly greater decrease in pain than the land-based exercise group before and after the 50FWT at the week-18 follow-up. DISCUSSION AND CONCLUSION: Both water-based and land-based exercises reduced knee pain and increased knee function in participants with OA of the knee. Hydrotherapy was superior to land-based exercise in relieving pain before and after walking during the last follow-up. Water-based exercises are a suitable and effective alternative for the management of OA of the knee.     

Treatment of pruritus of primary biliary cirrhosis with rifampin

Pruritus can be a debilitating symptom in patients with chronic cholestasis. Based on previous reports of its efficacy, we evaluated the impact of rifampin on the pruritus associated with primary biliary cirrhosis. Fourteen patients were included in a randomized, crossover study. After a 15-day washout period, subjects were followed for three weeks. During the first and third week, patients received 600 mg of rifampin or placebo; no treatment was administered during the second week. Pruritus was subjectively scored on a scale from 0 to 100. With rifampin, pruritus disappeared in 11 patients and partially improved in three; with placebo, only two had a partial response (P<0.001). Six patients with a prior poor or no response to cholestyramine improved with rifampin. No changes in biochemical tests or side effects were observed during this period. We conclude that short-term administration of rifampin relieves pruritus in primary biliary cirrhosis. When administered over a period of eight months in an open study, the relief of pruritus was maintained, while one individual developed an allergic reaction. Rifampin appears to be a safe drug in the management of the pruritus of primary biliary cirrhosis.     

Dynamics of T cells subsets and lymphoproliferative responses during structured treatment interruption cycles and after definitive interruption of HAART in early chronic HIV type-1-infected patients

Little is known about the consequences of short cycles of structured treatment interruption or definitive interruption of HAART for both T cell subset dynamics and T lymphoproliferative responses (LPR). Immunological follow-up was performed in 45 early chronical HIV-1-infected patients during short STI cycles during the first 12 weeks after the definitive interruption of HAART (DTI) and, thereafter, until VL reached a plateau. During STI cycles, CD8(+), CD8(+), CD28(+), activation markers and naive CD4(+) T cells increased significantly (p < 0.0001), while both naive CD8(+) and memory CD4(+) T cells decreased. During DTI, CD8(+) CD28(+) T cells fell and CD4(+) naive T cells stabilized and the rest of the T cell subsets presented changes similar to those during STI cycles. Despite a transient increase in LPR to recall antigens and HIV proteins during STI cycles, LPR to polyclonal stimuli and pathogens decreased over the study. Differences in T cell subset dynamics and LPR observed throughout the study suggest that multiple exposures to low levels of antigen could improve the immune system, mainly by driving T cell maturation. Conversely, higher and longer viral replication after cessation of HAART overwhelms the immune system. These data may help to guide future immune-based therapies.