Background/Aims: Inflammation of the mammary gland (mastitis) caused by invading pathogens is common among lactating dairy cows and causes great economic losses. We recently demonstrated that Chinese propolis (CP), a resinous substance collected by honeybees, can positively influence anti-inflammatory processes and antioxidant defense systems in vivo but little is known about how propolis treatment of mastitis in dairy cows may influence these activities.
Methods: We investigated the potentially protective effects of CP on aspects of mastitis by usingan in vitro model ofmastitis-induced cell damage involving cultured bovine mammary epithelial cells (MAC-T) which received a range of mastitis pathogen-related insults. Cell viability was measured by cell counting kit (CCK)-8 cell viability assay and expression of inflammatory/antioxidant genes were measured by qPCR. Using a cell-based reporter assay system, we evaluated CP and its main constituents’ on NF-κB and Nrf2-ARE transcription activity.
Results: Treatment of cells withcell wall components lipopolysaccharide (LPS), heat inactivated E. coli and S. aureus, but not TNF-α or lipoteichoic acid (LTA), significantly decreased cell viability (p<0.01). CP pretreatment (15μg/ml) significantly (p<0.05) protected cell viability losses CP pretreatment of MAC-T cells resulted in less impact on IL-6 and TNF-α mRNA expressions but increased expression of antioxidant genes HO-1, Txnrd-1 and GCLM. CP and its polyphenolic active components (mainly CAPE and quercetin) had strong inhibitive effects against NF-κB and increased the transcriptional activation of the Nrf2-ARE pathway.
Conclusions: Our findings support the usage of dietary propolis for the treatment of bovine mastitis.
Funding source: NSFC