Abstract:
Psoriasis vulgaris is a common disease with unknown pathogenesis. The treatment of the disease remains a challenge internationally due to the remission and recurrence nature of the disease. Psoriasis vulgaris was recently reported as an independent risk factor for ischaemic heart diseases, thromboembolic events and cerebrovascular accidents due to the higher level of plasma homocysteine in these patients, the result of defective methylenetetrahydrofolate reductase (MTHFR) enzymes. If these factors are strongly associated, homocysteinaemia could be lowered by the supplementations of folic acid and vitamin B₁₂ therefore reducing the risk of ischaemic heart diseases, thromboembolic events and cerebrovascular accidents in the psoriasis vulgaris patients. Though previous studies in the Far-East (China) supported the strong association of the MTHFR 677 C > T gene polymorphism and psoriasis vulgaris, there were some contradicting studies reported in the West (Austria and the Czech Republic). Therefore, the investigation on the association of the MTHFR 677 C > T gene polymorphism (NM_005957) and psoriasis vulgaris patients amongst the Malaysian population i.e. the Chinese, Indian and Malay ethnic groups of the Asian origin would be useful. This study was designed according to the Declaration of Helsinki and was approved by the ethics committee of the International Medical University, Malaysia. Cases (n = 200) were patients with psoriasis vulgaris and controls (n = 167) were subjects that do not have any history of psoriasis vulgaris, were age- (± 5 years), gender- and race-matched with the cases. DNA was extracted from the whole blood of both the cases and controls. Polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis of the MTHFR gene were performed in the presence of Taqαl restrictive enzyme. There was no significant increase (p = 0.392) of the MTHFR gene polymorphism (677 C > T) between cases and controls in the Malaysian population. Two homozygous mutations were seen in the controls and none in the cases. Subsequently, subsets of these cases (n = 41) and controls (n = 43) were age- (± 5 years), gender- and race-matched and selected for the determination of serum homocysteine, vitamin B₁₂ and folic acid levels. Though the highest homocysteine level was seen in the cases with heterozygous mutation to the MTHFR gene, the association was not statistically significant (p = 0.27). Homocysteine levels in cases were negatively correlated with vitamin B₁₂(r = -0.173) and folic acid (r = -0.345) levels. Skin biopsies were obtained from psoriasis vulgaris patients (n = 17) and non-psoriatic voluntary subjects who were undergoing their orthopaedic surgeries (n = 6). These biopsies were immuno-stained with antibodies against vascular endothelial growth factor (VEGF) subfamily- A, B, C, D and placenta growth factor (PIGF); nerve growth factor (NGF) and von Willebrand factor (vWFr). The VEGF-C (p = 0.016) and NGF (p = 0.027) were significantly expressed in the skin of psoriatic cases when compared with the controls. The NGF was the only marker that was solely expressed in the cases and absent in all the controls. No significant correlations between the angiogenesis markers staining intensities and PASI score or homocysteine levels were seen. In conclusion, no significant association between MTHFR gene polymorphism and psoriasis vulgaris amongst the Malaysian population i.e. the Chinese, Indian and Malay ethnic groups was seen. There was no association between the homocysteine level and psoriasis vulgaris in the Malaysian population. Significant expressions of NGF and VEGF-C in the cases may imply the importance of angiogenesis and lymphangiogenesis in the pathogenesis of the disease.
