In vitro expression of tumor necrosis factor-alpha, interleukin 1beta, and interleukin 8 mRNA by bovine macrophages following exposure to Porphyromonas levii.

The objective was to evaluate the pro-inflammatory response of bovine macrophages towards Porphyromonas levii, an etiologic agent of acute interdigital phlegmon, by evaluating the mRNA expression of tumor necrosis factor-alpha (TNF-alpha), interleukin 1beta (IL-1beta), and interleukin 8 (IL-8). Bovine macrophages detect the presence of bacteria, such as P. levii, and respond by upregulating transcription of the genes for pro-inflammatory cytokines TNF-alpha and IL-1beta in addition to the neutrophil chemoattractant IL-8. Monocytes were isolated from blood obtained from Holstein steers. These cells were cultured and differentiated into macrophages over 7 d, followed by exposure to P. levii, Escherichia coli lipopolysaccharide (LPS), or tissue culture medium for 1, 1.5, 2, 4, 6, 8,12, or 24 h. Total RNA was extracted, and reverse transcriptase polymerase chain reaction was conducted to examine the presence of TNF-alpha, IL-1beta, or IL-8 mRNA. Products were visualized on agarose gels to determine the presence or absence of cytokine mRNA amplified DNA. Bovine macrophages, when exposed to P. levii or E. coli LPS, produced mRNA for TNF-alpha, IL-1beta, and IL-8. Expression of all 3 cytokines was higher in the P. levii and LPS-exposed macrophages at all time points examined, compared with tissue culture medium-treated cells. Expression of these cytokines by macrophages is likely directly involved in orchestration of the immune response, and particularly in neutrophil recruitment to affected tissues in acute interdigital phlegmon.