MAB3828 Sigma-AldrichAnti-Mucin 5B Antibody, clone 15.5B

This study investigated the expression of MUC5B by AMs in the lungs of cigarette smokers and nonsmokers. We analyzed MUC5B expression by measuring the levels of apomucin and mRNA in human BALF cells from 50 subjects (20 nonsmokers, 17 patients with CB, and 13 patients with COPD). apoMUC5B was observed in BALF mononuclear cells in 60% of all subjects, but a significantly higher frequency of apoMUC5B(+) cells was found in subjects with CB (95% CI, 4.5-24.9) or COPD (95% CI, 6.2-39.6) than in nonsmokers (95% CI, 0.5-2.5). apoMUC5B(+) mononuclear cells showed strong expression of CD163, confirming their identity as AMs. MUC5B mRNA expression was detected by ISH in AMs of subjects investigated, and real-time qPCR analysis confirmed MUC5B mRNA expression. In conclusion, MUC5B is expressed in a subset of lung AMs and long-term cigarette smoking may increase the level of MUC5B produced by these cells.

Thioredoxin (Trx) decreases viscosity of cystic fibrosis (CF) sputum. In this study reduced Trx increased the solubility and decreased the size of MUC5B glycoprotein while reducing disulfide bonds in sputum. Because Trx used as a mucolytic would enter airways, this study determined the effects of intratracheal instillation of reduced recombinant human thioredoxin (rhTrx) in naïve rat airways. Reduced rhTrx increased neutrophils and the cytokines TNFalpha, CINC2beta, and MIP3alpha in airways after 4 h. The effect of rhTrx was concentration-dependent. Exposure to saline, human serum albumin, or oxidized rhTrx at equal molarities did not increase airway neutrophils or cytokines. Instilling CF sputum (50 microl) into the lung before reduced rhTrx delivery attenuated these responses. This suggests that rhTrx reduces disulfide bonds present in CF sputum, limiting the reduction of other lung constituents. Together these findings indicate that the chemotactic and cytokine responses are due to the reducing potential of rhTrx and that the potential for inflammation in non-CF and CF patients given aerosolized rhTrx may differ. In parallel studies, increased amounts of the p65 subunit of NF-kappaB were present in nuclear extracts from rat lungs administered reduced rhTrx, suggesting a role for NF-kappaB in these proinflammatory responses.

The MG1 population of mucins was isolated from human whole salivas by gel chromatography followed by isopycnic density gradient centrifugation. The reduced and alkylated MG1 mucins, separated by anion exchange chromatography, were of similar size (radius of gyration 55-64 nm) and molecular weight (2.5-2.9 x 10(6) Da). Two differently-charged populations of MG1 subunits were observed which showed different reactivity with monoclonal antibodies to glycan epitopes. Monosaccharide and amino acid compositional analyses indicated that the MG1 subunits had similar glycan structures on the same polypeptide. An antiserum recognizing the MUC5B mucin was reactive across the entire distribution, whereas antisera raised against the MUC2 and MUC5AC mucins showed no reactivity. Western blots of agarose gel electrophoresis of fractions across the anion exchange distribution indicated that the polypeptide underlying the mucins was the product of the MUC5B gene. Amino acid analysis and peptide mapping performed on the fragments produced by trypsin digestion of the two MG1 populations yielded data similar to that obtained for MUC5B mucin subunits prepared from respiratory mucus (Thornton et al., 1997) and confirmed that the MUC5B gene product was the predominant mucin polypeptide present. Isolation of the MG1 mucins from the secretions of the individual salivary glands (palatal, sublingual, and submandibular) indicate that the palatal gland is the source of the highly charged population of the MUC5B mucin.