Protocatechuic acid suppresses ovalbumin-induced airway inflammation in a mouse allergic asthma model

Protocatechuic acid (PCA) has been isolated from the leaves of ilex chinenses and has numerous pharmacologic effects, including anti-inflammatory and antitumoral activities. This study aims to evaluate the antiasthma activity of PCA and investigate its possible molecular mechanisms. BALB/c mice were sensitized and challenged to ovalbumin (OVA).Then mice were intraperitoneally (i.p.) injected with PCA 1h before OVA challenge. We found that PCA treatment at 15 or 30 mg/kg significantly decreased OVA-induced airway hyper-responsiveness (AHR) to inhaled methacholine. Type 2 helper T cell (Th2) cytokines in bronchoalveolar lavage (BAL) fluid, such as interleukin-4 (IL-4), interleukin 5 (IL-5) and interleukin-13 (IL-13), and serum OVA-specific immunoglobulin E (IgE) levels, were also reduced by PCA. Moreover treatment with PCA markedly decreased the number of inflammatory cells in BALF and attenuated OVA-induced mRNA expression of CCl11, CCR3, Muc5ac, acidic mammalian chitinase (AMCase), chitinase 3-like protein 4 (Ym2) and E-selectin in lung tissues, lung histopathological studies showed that PCA inhibited inflammatory cell infiltration and mucus hypersecretion compared with the OVA-induced mice group. We then investigated the possible molecular mechanisms which might be implicated in PCA activity. Our results suggested that the protective effect of PCA might be mediated by the inhibition of the extracellular signal-regulated protein kinase (ERK), p38 Mitogen-activated protein kinase (MAPK) phosphorylation and the nuclear factor-κB (NF-κB) activation.