Relationship Between 5-HTR1A C(-1019)G And G-Protein β3 Subunit C825T Polymorphisms And Post-Stroke Depression

IntroductionPost-stroke depression is a common complication after stroke, for the main performance of continual depressive disorders, lack of interest and pleasure. PSD will affect patients with neurological recovery, activities of daily living and cause social withdrawal. It also can longer length of hospital stay, and increase disability and mortality. Therefore, more and more medical professionals focus on this aspect.Varing in previous studies, the prevalence of PSD was reported by 20% to 79%, majourity around 40% to 50%. The data is diverse in different periods. A systematic evaluation summarized 51 research based on population, hospital or rehabilitation facility, which were during 1977-2002. The prevalence of PSD were different from each other, after merger analysis in all stroke survivors prealence of depression was 33% during follow-up. Varies sample selection bias and depression evaluation method can partly explain the difference of morbidity among the studies. Overall, PSD is prevalent, it increases disability and fatality in stroke survivors. So it has important strategic significance to verify its pathogenesis in preventing PSD.The pathogenesis of PSD is uncertainty.There are two prevailing hypothesis. One is biological mechanism, considering that brain vascular lesions caused monoamine neurotransmitters and emotional adjustment nerve pathways function abnormality; the other is psychological mechanism, claims that the social and psychological factors are the main etiology. Although function disabled may cause people's emotional responses, early controlled study found the PSD incidence far higher than similar disability degree of orthopaedic or other diseases. It indicated that biological factors had participated in the pathogenesis besides psychological reaction. Monoamine system, such as norepinephrine and serotonin, plays roles in regulating mood and emotion. Noradrenergic and serotonergic neurons originate in the dorsal and median raphe nucleus of the brainstem. Going through hypothalamus and basal ganglia, the axons surround callosum and corona radiata, then reach throughout frontal cortex. When cerebrovascular lesions affect these structures, the monoamine balances is broken, resulting in depression. Animal research found declined serotonin, norepinephrine and dopamine in cortex, corpus striatum and hippocamp after ischemia and reperfusion, and suggested it may be associated with PSD incidence. Clinical studies also reported that serotonin, norepinephrine and dopamine decreased in plasma and cerebrospinal fluid of PSD patients. It also told that serotonin transporter gene-linked promotor region polymorphism is relevant to PSD. Lots of evidences confirmed serotonin system dysfunction implicated in the PSD.As one of the most abundantly expressed 5-HT receptors subtypes in central nervous system,5-HT1A receptors play an important role in regulation of neurotransmission.5-HT1A receptors are present in various regions of brain. The 5-HT1A atuoreceptors are located presynaptically on the soma and dendrites of serotonergic neurons in the raphe nucleus. Aciviation of 5-HT1A autoreceptors suppresses firing of serotonergic neurons and thus reduces activity-dependent serotonin release. They also regulate neurotransmission by negative feedback mechanism. The 5-HT1A heteroreceptors are located postsynaptically in the forebrain, such as cortex, hippocampus, septum, amygdala and hypothalamus. Activation of 5-HT1A heteroreceptors on these distinct neurons usually lead to cytomembrane hyperpolarization, resulting in reducing neuronal excitability and firing. In recently years, it was found that variation of the gene for human 5-HT1A receptors implicated in mood disorders. The single nucleotide C(-1019)G polymorphism located on 5-HTR1A promoter was widely studied, these research confirmed that (-1019)G allele and G/G genotype can predispose to depression. The C(-1019) allele was part of a 26 bp imperfect palindrome that bound transcription factors nuclear NUDR [nuclear deformed epidermal autoregulatory factor (DEAF-1)]/suppressin and Hairy/Enhancer-of split-5 (Drosophila) (Hes5) to repress 5-HT1A or heterologous promoters, whereas the (-1019)G allele abolished repression by NUDR, but only partially impaired Hes5-mediated repression, thus 5-HT1A receptors expression were regulated. So we supposed that 5-HT1A receptors promoter C(-1019)G polymorphism may be associated with post-stroke depression.Hypothesis on monoamine neurotransmitters and receptors can partly explain depressive symptom following stroke, but it can not expound the mechanism. Otherwise, a series of complex physiopathology process, such as neurons lesions and synaptic plasticity caused by stroke, may be participated in occurrence of PSD, so people threw light on signal transduction system.5-HT1A receptors belong to the G-protein coupled receptor (GPCR) family. The 5-HT1A receptors couple to G-protein to trigger downstream signaling events. Consequently, G-protein was focused as the base of transmembrane signaling and hinge of nerve pathways, especially for G-proteinβ3 subunit (GNβ3) gene. Siffert described a C825T polymorphism in the gene GNβ3, which bring about the splice variant GNP3s. Despite a deletion of 41 amino acid, GNβ3s is functionally active. In cellular level, the C825T polymorphism is associated with transformation of signal transduction, which is mediated by the inhibitory G-protein (Gi), and detected its affects on etiology of depression, as well as antidepressant therapy. Now we emphasis on the GNβ3 C825T polymorphism, which has not been reported on PSD.Objective:The purpose of this experiment was to assess whether 5-HT1A receptor gene C(-1019)G and GN03 C825T gene polymorphisms are associated with post-stroke depression(PSD) and explore the genetic mechanism of post-stroke depression.Methods:All 162 patients with first stroke were inpatients of the neurology department of Zhujiang Hospital. They were diagnosed according to the criteria on stroke from the Fourth National Cerebrovascular Diseases Conference. The extent of the depressive state was assessed by a 24-item "Hamilton Depression Rating Scale"(HAMD). Subjects, including 33 males and 20 females, were classified as post-stroke depression group when they showed a score of more than 20 on HAMD and corresponded with the DSM-IV criteria for a major depressive episode. Subjects with 73 males and 36 females were classified as stroke group when they showed a score below and did not show any symptoms of the major depression disorder in the DSM-IV criteria for more than 2 weeks. EDTA anticoagulated blood samples were collected, and genomic DNA was isolated with phenolic-chloroform. Polymerase chain reaction-restriction fragment length polymorphism technology was applied. Upstream primer 5'-GTGGCGACATAAAACCTCA-3'and downstream primer 5'-TTCTTAAATCGTGTCAGCATC-3'were used for the amplification of 5-HTR1A C(-1019)G gene, the PCR product was sequenced to detect Câ†'G polymorphism. Upstream primer 5'-TGACCCACTTGCCACCCGTGC-3'and downstream primer 5'-GCAGCAGCCAGGGCTGGC-3'were used for the amplification of GNβ3 C825T gene. BsaJI restriction endonuclease was applied to detect the Câ†'T polymorphism. SPSS 13.0 statistical package was employed in data analysis.X2 analysis was used to compare genotype frequencies between stroke patients with and without depression, as well as allele frequencies.Results:The data analysis showed that there was no significant difference in age, gender, and infarction vs haemorrhage between two groups.58.5% of PSD patients were with allele C and 41.5% with allele G, while in the stroke group 81.2% were with allele C and 18.8% with allele G. There was a significant difference between the two groups (X2=18.994, P<0.001, OR=3.064, 95%CI=1.832-5.125).The PSD groups has significant higher rate of allele G. In the case group, the genotype frequencies distributions of C/C, C/G and G/G in 5-HTR1A C(-1019)G gene were 32.1%,52.8% and 15.1% respectively, while in the control group were 69.7%,22.9% and 7.3%. There was a significant difference between the two groups (X2=20.718, P<0.001)35.8% of PSD patients were with allele C and 64.2% with allele T, while in the stroke group 47.7% were with allele C and 52.3% with allele T. There was a significant difference between the two groups(X2=4.073, P=0.044, OR=1.633,95%CI =1.012-2.632).The PSD groups has significant higher rate of allele T. In the case group, the genotype frequencies distributions of C/C, C/T and T/T in GN03 C825T gene were 15.1%,41.5% and 43.4% respectively, while in the control group were28.4%,38.5% and 33.0%. The T/T genotype frequencies of patients with PSD was higher than the patients without, but there was no significant difference between the two groups (X2=3.771, P=0.152)Combined genotype analysis showed that individuals with both 5-HTR1A (-1019)G and GNβ3825T allele (OR=5.804,95%CI=2.802-12.023) had a higher risk than those only with 5-HTR1A (-1019)G allele(OR=3.064,95%CI=1.832-5.125) or GNβ3 825T allele (OR=1.633,95%CI=1.012-2.632) for post-stroke depression. Conclusion:1. Significant differences of genotype frequencies and allele frequencies in 5-HTR1A C(-1019)G gene were found in patients with and without PSD, which indicated that 5-HTR1A C(-1019)G polymorphism may be predisposing gene of post-stroke depression, and carrying mutant gene G will increase the incidence of PSD.2. There was a significant difference of allele frequencies in GNβ3 C825T gene in PSD group and stroke group, which suggested that GNβ3 C825T polymorphism may be predisposing gene of post-stroke depression, and T allele plays a role in post-stroke depression.3. Our results suggested a significant interaction between 5-HTR1A (-1019)G allele and GNβ3 825T allele, because of the higher risk for PSD with both mutant gene.