Association Between Surfactant Protein A And D Gene Variation And Susceptibility To Recurrent Urinary Tract Infection

Surfactant Proteins are produced and secreted by Alveolar typeⅡcells and Clare cells, including hydrophilic surfactant proteins A and D (SP-A and SP-D),and the hydrophobic surfactant proteins B and C (SP-B and SP-C). Human SP-A and SP-D genes are located on the chromosome 10q22-q23. It is suggested that SP-A consists of one SP-A1 and two SP-A2 molecules. Both SP-A1 and SP-A2 transcripts are expressed in adult human alveolar typeⅡcells. However, SP-A1 and SP-A2 genes are differentially expressed in different tissues. Both of the SP-A1 and SP-A2 transcripts have been expressed in the human small and large intestine, whereas only the SP-A2 gene was predominantly detected in the epithelium of reproductive system. Kidney is the critical interface exposed to foreign and potentially harmful substances as the lung, we presume that the kidney could be one of the site in which hydrophilic surfactant protein A and D can also be expressed.Both SP-A and SP-D belong to the C-type lectin superfamily and keep pulmonary alveoli from collapsing at the end of expiration. It has been demonstrated that these molecules can participate in innate immune response and regulate inflammatory processes The genetic variations of SP-A1, SP-A2 and SP-D genes have been reported to be related with susceptibility to several infective diseases, such as respiratory syncytial virus infection, meningitis.Urinary tract infection (UTI) remains one of the common infections affecting adult female. The host genetic factor has been considered as one of the pathogenesis of r-UTI. However, the specific genes involved remained largely unknown. Therefore, we presume theoretically the polymorphisms of SP-A and SP-D gene would be associated with the recurrence of r-UTI.To prove the hypothesis, the current study includes two parts to further explore the expression of SP-A subtypes and SP-D in human kidney and to investigate the association between genetic variants in the exonic regions of SP-A and SP-D genes and r-UTI susceptibility.Objective:To determine the SP-A subtypes and SP-D distributions and expressions in human kidney and cultured human renal tubular epithelial cells(HK-2).Methods:Immunohistochemical staining were performed using SP-A and SP-D polyclonal antibodies. RT-PCR was performed with mRNA from HK-2 cells and human kidney. The analysis of SP-A subtypes in HK-2 cells was performed by RFLP and Sequencing.Western blotting analysis for SP-A and SP-D were performed on protein from kidney and cultured HK-2 cells. Measurement and immunoreactivity of SP-A and SP-D in urine and culture medium samples of HK-2 cells was defined by enzyme-linked immunosorbent assay (ELISA) and Western blotting respectively.Results:SP-A and SP-D protein were localized in renal tubular epithelial cells of both proximal and distal convoluted tubule. Both SP-A1, SP-A2 and SP-D mRNA and protein could be detected in HK-2 cells and human kidney. The significant secretion of SP-A(Urine:106.614±72.772 pmol/mL; Culture medium:85.533±58.622 pmol/mL) and SP-D(Urine:59.112±45.585 pmol/mL; Culture medium:34.082±26.337 pmol/mL) from HK-2 cells were shown.Conclusions:Human kidney and human renal tubular epithelial cells have a significant expression of SP-A1, SP-A2 and SP-D.Objective:SP-A and SP-D play an important role in pulmonary surfactant-related function, modulation of inflammatory processes, and host defense. Recent studies have demonstrated the expression of SP-A and SP-D in kidney. We examined whether single nucleotide polymorphisms (SNPs) of human SP-A (SP-A1 and SP-A2) and SP-D were associated with recurrence of urinary tract infection in adult female in Chinese population.Methods:Genomic DNA was extracted from blood samples of 32 female patients with recurrent UTI (r-UTI) and 30 age-matched, unrelated control healthy female subjects (HS). SP-A1(Ala19Val, Leu50Val, Pro62Pro, Thr133Thr and Arg219Trp), SP-A2 (Thr9Asn, Pro91Ala, Ser140Ser and Lys223Gln) and SP-D (ThrllMet and Thr160Ala) SNPs were analyzed by sequence special primer polymerase chain reaction (PCR-SSP). Serum and urine SP-A and SP-D proteins were measured using ELISA method.Results:The allele and genotype frequencies of SP-A1-Leu50Val, SP-A1-Pro62Pro, SP-A1-Thr133Thr, SP-A1-Arg219Trp, SP-A2-Thr9Asn, SP-A2-Pro91Ala, SP-A2-Ser140Ser, SP-D-ThrllMet, SP-D-Thr160Ala loci showed no significantly difference between two groups(p> 0.05). The frequencies of Ala/Ala,Ala/Val,Val/Val genotypes were 18.8%,62.4% and 18.8% in r-UTI patients and 13.3%,36.7%,50.0% in HS subjects respectively(P< 0.05). The frequencies of Gln/Gln, Lys/Gln, Lys/Lys genotypes were 68.8%,21.9% and 9.3% in r-UTI patients and 36.7%,43.3%,20.0% in HS subjects respectively(P< 0.05). Statistical analysis indicated that the frequencies of genotypes at SP-A1-Alal9Val and SP-A2-Lys223Gln loci showed significant difference between two groups.The frequencies of 19Ala allele in SP-A1-Alal9Val and 223Gln allele in SP-A2-Lys223Gln loci were significantly higher in r-UTI patients than in HS subjects(P< 0.05). The serum SP-A and SP-D levels were significantly increased and the urine SP-A and SP-D levels were significantly decreased in r-UTI patients compared with HS subjects(P< 0.05). r-UTI patients with 19Ala/Ala or 223Gln/Gln genotype were associated with high serum and low urine SP-A levels (p< 0.05).Conclusions:The 19Ala alleles of SP-A1 gene and the 223Gln allele of SP-A2 gene are risk factors for r-UTI in Chinese Women.