Differential expression of sheep beta-defensin-1 and -2 and interleukin 8 during acute Mannheimia haemolytica pneumonia

Microb Pathog. 2004 Jul;37(1):21-7. doi: 10.1016/j.micpath.2004.04.003.

Abstract

Beta-defensins are antimicrobial peptides produced by several cell types, including respiratory epithelia and leukocytes. Expression of some beta-defensins is increased by bacterial-induced inflammatory responses whereas expression of other beta-defensins is constitutive. Two beta-defensins are expressed in lungs of sheep (sheep beta-defensin-1 and -2; SBD-1/-2) and expression of SBD-1 is increased during parainfluenza virus type 3 (PI-3) infection. The effect of Mannheimia haemolytica, a Gram-negative bacteria known to induce expression of bovine beta-defensins and NF-kappa B in lung, has not been determined for SBD-1/-2. In this study, different concentrations of M. haemolytica were inoculated into pulmonary bronchi of lambs. SBD-1 and SBD-2 mRNA levels detected by real time reverse transcriptase polymerase chain reaction in lung homogenates did not increase. In fact, SBD-1 mRNA levels were significantly decreased with the highest administered inoculum concentration (10(9)). In contrast, mRNA levels of interleukin-8 (IL-8) were significantly increased over controls and progressively increased with M. haemolytica concentrations. Co-inoculation of M. haemolytica with xylitol, an osmotic agent, did not alter mRNA levels of SBD-1, SBD-2 or IL-8. SBD-1 mRNA expression was detected in lung epithelia, but not in leukocytes. This study suggests that SDB-1 expression occurs in epithelia and decreases during severe bacterial pneumonia, which is in contrast to the increase that occurs with PI-3 infection.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Bronchoalveolar Lavage Fluid / microbiology
  • Gene Expression
  • Interleukin-8 / biosynthesis*
  • Interleukin-8 / genetics
  • Leukocytes / immunology
  • Leukocytes / metabolism
  • Lung / immunology
  • Mannheimia haemolytica / immunology*
  • Mannheimia haemolytica / isolation & purification
  • Pasteurellaceae Infections / immunology
  • Pasteurellaceae Infections / microbiology
  • Pasteurellaceae Infections / veterinary*
  • Pneumonia, Bacterial / immunology
  • Pneumonia, Bacterial / microbiology
  • Pneumonia, Bacterial / veterinary*
  • Polymerase Chain Reaction
  • RNA, Messenger / analysis
  • RNA, Messenger / biosynthesis
  • Respiratory Mucosa / immunology
  • Sheep
  • Sheep Diseases / immunology*
  • Sheep Diseases / microbiology
  • Transcription, Genetic
  • beta-Defensins / biosynthesis*
  • beta-Defensins / genetics

Substances

  • Interleukin-8
  • RNA, Messenger
  • beta-Defensins