Effects of laxative and N-acetylcysteine on mucus accumulation, bacterial load, transit, and inflammation in the cystic fibrosis mouse small intestine

Am J Physiol Gastrointest Liver Physiol. 2007 Sep;293(3):G577-84. doi: 10.1152/ajpgi.00195.2007. Epub 2007 Jul 5.


The accumulation of mucus in affected organs is characteristic of cystic fibrosis (CF). The CF mouse small intestine has dramatic mucus accumulation and exhibits slower interdigestive intestinal transit. These factors are proposed to play cooperative roles that foster small intestinal bacterial overgrowth (SIBO) and contribute to the innate immune response of the CF intestine. It was hypothesized that decreasing the mucus accumulation would reduce SIBO and might improve other aspects of the CF intestinal phenotype. To test this, solid chow-fed CF mice were treated with an osmotic laxative to improve gut hydration or liquid-fed mice were treated orally with N-acetylcysteine (NAC) to break mucin disulfide bonds. Treatment with laxative or NAC reduced mucus accumulation by 43% and 50%, respectively, as measured histologically as dilation of the intestinal crypts. Laxative and NAC also reduced bacterial overgrowth in the CF intestine by 92% and 63%, respectively. Treatment with laxative normalized small intestinal transit in CF mice, whereas NAC did not. The expression of innate immune response-related genes was significantly reduced in laxative-treated CF mice, whereas there was no significant effect in NAC-treated CF mice. In summary, laxative and NAC treatments of CF mice reduced mucus accumulation to a similar extent, but laxative was more effective than NAC at reducing bacterial load. Eradication of bacterial overgrowth by laxative treatment was associated with normalized intestinal transit and a reduction in the innate immune response. These results suggest that both mucus accumulation and slowed interdigestive small intestinal transit contribute to SIBO in the CF intestine.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcysteine / pharmacology*
  • Acetylcysteine / therapeutic use
  • Animals
  • Bacteria / drug effects*
  • Bacteria / genetics
  • Bacteria / growth & development
  • Body Weight / drug effects
  • Cathartics / pharmacology*
  • Cathartics / therapeutic use
  • Cystic Fibrosis / drug therapy*
  • Cystic Fibrosis / metabolism
  • Cystic Fibrosis / microbiology
  • Cystic Fibrosis / physiopathology
  • Disease Models, Animal
  • Expectorants / pharmacology*
  • Expectorants / therapeutic use
  • Gastric Emptying / drug effects
  • Gastrointestinal Transit / drug effects*
  • Gene Expression Regulation / drug effects
  • Immunity, Innate / drug effects
  • Immunity, Innate / genetics
  • Inflammation / drug therapy*
  • Inflammation / metabolism
  • Inflammation / microbiology
  • Inflammation / physiopathology
  • Intestine, Small / drug effects*
  • Intestine, Small / metabolism
  • Intestine, Small / microbiology
  • Intestine, Small / physiopathology
  • Mice
  • Mice, Inbred CFTR
  • Mucus / metabolism*
  • Polyethylene Glycols / pharmacology*
  • Polyethylene Glycols / therapeutic use
  • RNA, Bacterial / metabolism
  • RNA, Ribosomal, 16S / metabolism


  • Cathartics
  • Expectorants
  • RNA, Bacterial
  • RNA, Ribosomal, 16S
  • Polyethylene Glycols
  • Acetylcysteine