Melissa officinalis L. protects against reflux esophagitis by attenuating NF-κB- and MAPK-mediated inflammation in rats

Ethnopharmacological relevance: Melissa officinalis L. is a medicinal plant that has long been used in traditional medicine for gastrointestinal-related conditions. This traditional background provides an ethnopharmacological rationale for investigating its potential effects on inflammatory disorders of the upper gastrointestinal tract. Nevertheless, evidence regarding its protective role in reflux esophagitis remains limited. Aim of study: This study aimed to determine the protective effects of M. officinalis L. extract against reflux esophagitis and to elucidate its underlying anti-inflammatory mechanisms. Materials and methods: The antioxidant activities and anti-inflammatory effects of M. officinalis L. extract were assessed using in vitro assays, including suppression of nitric oxide (NO) release and inflammatory mediator expression from lipopolysaccharide (LPS)-activated RAW 264.7 cells. The activation of the NF-κB and MAPK signaling pathways (ERK, p38, and JNK) and the expression of COX-2 and iNOS were analyzed by Western blotting. In vivo, M. officinalis L. extract was orally administered to rats with acute reflux esophagitis. Esophageal damage was evaluated macroscopically and histologically. The expression of MAPK signaling proteins, pro-inflammatory cytokines (TNF-α and IL-1β), and tight junction (TJ) proteins was evaluated by Western blotting. In addition, rosmarinic acid (RA), identified and quantified by HPLC as a characteristic marker compound, was evaluated for its nitric oxide inhibitory activity and its effects on NF-κB/MAPK signaling in vitro. Results: M. officinalis L. extract exhibited dose-dependent antioxidant activity and reduced nitric oxide production in LPS-stimulated RAW 264.7 cells. M. officinalis L. extract inhibited phosphorylation of NF-κB and MAPKs (ERK, p38, and JNK) and downregulated COX-2 and iNOS expression in macrophages. In rats with reflux esophagitis, M. officinalis L. extract alleviated mucosal damage and preserved tissue structure. These protective effects were associated with suppressed MAPK activation, reduced TNF-α and IL-1β expression, and restored tight junction protein levels in esophageal tissues. Rosmarinic acid showed nitric oxide inhibitory activity and modulated NF-κB/MAPK signaling in vitro. Conclusion: This study presents experimental evidence that M. officinalis L. extract attenuates reflux esophagitis by regulating NF-κB/MAPK signaling pathways and preserving mucosal integrity. These findings support the potential relevance of M. officinalis L. in the context of esophageal inflammatory conditions.