Aquaporin 5 Interacts with Fluoride and Possibly Protects Against Caries

Aquaporins (AQP) are water channel proteins and the genes coding for AQP2, AQP5, and AQP6 are clustered in 12q13. Since AQP5 is expressed in serous acinar cells of salivary glands, we investigated its involvement in caries. DNA samples from 1,383 individuals from six groups were studied. Genotypes of eight single nucleotide polymorphisms covering the aquaporin locus were tested for association with caries experience. Interaction with genes involved in enamel formation was tested. The association between enamel microhardness at baseline, after creation of artificial caries lesion, and after exposure to fluoride and the genetic markers in AQP5 was tested. Finally, AQP5 expression in human whole saliva, after exposure to fluoride in a mammary gland cell line, which is known to express AQP5, and in Wistar rats was also verified. Nominal associations were found between caries experience and markers in the AQP5 locus. Since these associations suggested that AQP5 may be inhibited by levels of fluoride in the drinking water that cause fluorosis, we showed that fluoride levels above optimal levels change AQP5 expression in humans, cell lines, and rats. We have shown that AQP5 is involved in the pathogenesis of caries and likely interact with fluoride.Fil: Anjomshoaa, Ida. University of Pittsburgh; Estados UnidosFil: Briseño Ruiz, Jessica. University of Pittsburgh; Estados UnidosFil: Deeley, Kathleen. University of Pittsburgh; Estados UnidosFil: Poletta, Fernando Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET.; ArgentinaFil: Mereb, Juan C.. Provincia de Río Negro. Ministerio de Salud. Hospital de Área El Bolsón ; ArgentinaFil: Leite, Aline L.. Universidade de Sao Paulo; BrasilFil: Barreta, Priscila A. T.. Universidade de Sao Paulo; BrasilFil: Silva, Thelma L.. Universidade de Sao Paulo; BrasilFil: Dizak, Piper. University of Pittsburgh; Estados UnidosFil: Ruff, Timothy. University of Pittsburgh; Estados UnidosFil: Patir, Asli. İstanbul Medipol Üniversitesi; TurquíaFil: Koruyucu, Mine. İstanbul Üniversitesi; TurquíaFil: Abbasoğlu, Zerrin. Yeditepe Üniversitesi; TurquíaFil: Casado, Priscila L.. Universidade Federal Fluminense; BrasilFil: Brown, Andrew. University of Pittsburgh; Estados UnidosFil: Zaky, Samer H.. University of Pittsburgh; Estados UnidosFil: Bayram, Merve. İstanbul Medipol Üniversitesi; TurquíaFil: Küchler, Erika C.. University of Pittsburgh; Estados UnidosFil: Cooper, Margaret E.. University of Pittsburgh; Estados UnidosFil: Liu, Kai. University of Pittsburgh; Estados UnidosFil: Marazita, Mary L.. University of Pittsburgh; Estados UnidosFil: Tanboğa, İlknur. Marmara Üniversitesi; TurquíaFil: Granjeiro, José M.. Universidade Federal Fluminense; Brasil. Instituto Nacional de Metrologia, Qualidade e Tecnologia; BrasilFil: Seymen, Figen. İstanbul Üniversitesi; TurquíaFil: Castilla, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET.; Argentina. Fundación Oswaldo Cruz; BrasilFil: Orioli, Iêda M.. Universidade Federal do Rio de Janeiro; BrasilFil: Sfeir, Charles. University of Pittsburgh; Estados UnidosFil: Owyang, Hongjiao. Marmara Üniversitesi; TurquíaFil: Rabelo Buzalaf, Marilia Afonso. Universidade de Sao Paulo; BrasilFil: Vieira, Alexandre R.. University of Pittsburgh; Estados Unido

<i>AQP5</i> expression in whole saliva based on caries experience in teenagers (above) and adults (below).

<p>The expression is higher when individuals have lower caries experience. The increased expression in adults classified as high caries experience likely corresponds to lack of caries activity as assessed by the increased number of missing teeth rather that active decayed teeth. Caries experience was defined as “Very Low,” “Low,” “Moderate,” and “High” according to our previous work [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143068#pone.0143068.ref017" target="_blank">17</a>]. These discreet groups include caries experience levels taking into consideration ages, since DMFT scores tend to increase in individuals as they get older.</p

Linkage disequilibrium plot illustrating the aquaporin locus on 12q13 region investigated.

<p>The single nucleotide polymorphisms are located in their approximate geographic positions in the chromosome and are distributed among the three genes. The relationship between two SNPs is represented by the intersection between the two squares and may present different colors (or color intensity) based on the value obtained for each pair. Red indicates D’ = 1 and LOD ≥ 2. Blue indicates D’ = 1 and LOD < 2. Shades of red/pink indicate D’< 1 and LOD ≥ 2. White indicates D’< 1 and LOD < 2. Markers selected for this studied include rs457487, rs467323, rs10875989, rs2878771, rs3759129, rs296759, rs296763, and rs1996315.</p

Arrows indicate sites where saliva samples were collected in Argentina.

<p>Red arrows indicate sites with very high frequency of cases with moderate to severe fluorosis and blue arrows sites where virtually no fluorosis cases were found.</p

<i>AQP5</i> expression in whole saliva is lower [N = 12 children (ch) and teenagers (teen)] in individuals with moderate to severe fluorosis [N = 34 children (ch) and teenagers (teen)].

<p><i>AQP5</i> expression in whole saliva is lower [N = 12 children (ch) and teenagers (teen)] in individuals with moderate to severe fluorosis [N = 34 children (ch) and teenagers (teen)].</p

Summary of all individuals analyzed in tests of association, gene expression, and enamel microhardness, and their genotypes^*.

<p>^a Decayed, Missing due to caries, Filled Teeth</p><p>^b Standard Deviation</p><p>* Totals may not match with sample sizes due to PCR failure.</p><p>Summary of all individuals analyzed in tests of association, gene expression, and enamel microhardness, and their genotypes^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143068#t001fn003" target="_blank">*</a>}.</p

Criteria used to define caries experience in the samples from Niterói, Brazil.

<p>Criteria used to define caries experience in the samples from Niterói, Brazil.</p

<i>AQP5</i> expression in mammary gland/breast adenocarcinoma cell line HTB-22^™ after exposure to higher concentrations of fluoride decreases.

<p><i>AQP5</i> expression in mammary gland/breast adenocarcinoma cell line HTB-22^™ after exposure to higher concentrations of fluoride decreases.</p