Evaluation of Plantago lanceolata (Ribwort Plantain) and StrepCough Plantain-Dry Cough Syrup in In Vitro Models of Pharyngitis and Cough

Symptoms of respiratory tract infections (RTI) caused by viral or bacterial triggers include sore throat and cough. Plantago lanceolata (ribwort plantain) is used in herbal medicine to treat symptoms of RTI. This study evaluated the pharmacological actions of P. lanceolata extract (PL) and StrepCough Plantain-Dry cough syrup (PLS) in in vitro models of sore throat and cough. Human tonsil epithelial cells (HTEpiC) cells were stimulated with a combination of lipoteichoic acid and peptidoglycan in the presence or absence of PL or PLS. Levels of TNF-α, IL-6, PGE₂, and COX-2 were measured using ELISA, while phospho-p65 protein levels were measured using Lumit® immunoassay. The effects of PL and PLS on bradykinin-induced inflammation and increased intracellular Ca²+ were investigated in bronchial epithelial cells (BEAS-2B), cells over-expressing TRPV1. Results showed that the pre-treatment of HTEpiC cells with PL and PLS resulted in a significant (p < 0.05) reduction in the LTA + PGN-induced increased production of TNFα, IL-6, PGE₂, as well as COX-2 and phospho-p65 protein levels. Bradykinin-induced increased levels of TNFα, IL-6, and PGE₂ in BEAS-2B cells over-expressing TRPV1 were also reduced by PL and PLS, while reducing levels of intracellular Ca²+. This study has demonstrated that extract of P. lanceolata and StrepCough Plantain-Dry cough syrup reduce inflammation in human tonsil epithelial cells. The extract and syrup also reduced TRPV1-mediated inflammation and increased intracellular Ca2+ in BEAS-2B bronchial epithelial cells. This study has provided pharmacological evidence for the use of P. lanceolata in healthcare interventions to treat symptoms of respiratory tract infection.