Usnic acid alleviates inflammatory responses and induces apoptotic signaling through inhibiting NF-ĸB expressions in human oral carcinoma cells.

Usnic acid (UA) is a unique bioactive substance in lichen with potential anticancer properties. Recently, we have reported that UA can reduce 7,12-dimethylbenz[a] anthracene-induced oral carcinogenesis by inhibiting oxidative stress, inflammation, and cell proliferation in a male golden Syrian hamster in vivo model. The present study aims to explore the relevant mechanism of cell death induced by UA on human oral carcinoma (KB) cell line in an in vitro model. We found that UA can induce apoptosis (cell death) in KB cells by decreasing cell viability, increasing the production of reactive oxygen species (ROS), depolarizing mitochondrial membrane potential (MMP) levels, causing nuclear fragmentation, altering apoptotic morphology, and causing excessive DNA damage. Additionally, UA inhibits the expression of Bcl-2, a protein that promotes cell survival, while increasing the expression of p53, Bax, Cytochrome-c, Caspase-9, and 3 proteins in KB cells. UA also inhibits the expression of nuclear factor-κB (NF-κB), a protein that mediates the activation of pro-inflammatory cytokines such as TNF-α and IL-6, in KB cells. Furthermore, UA promotes apoptosis by enhancing the mitochondrial-mediated apoptotic mechanism through oxidative stress, depletion of cellular antioxidants, and an inflammatory response. Ultimately, the findings of this study suggest that UA may have potential as an anticancer therapeutic agent for oral cancer treatments.

Usnic acid attenuates 7,12-dimethylbenz[a] anthracene (DMBA) induced oral carcinogenesis through inhibiting oxidative stress, inflammation, and cell proliferation in male golden Syrian hamster model.

In this study, we investigated the chemopreventive efficacy of usnic acid (UA), an effective secondary metabolite component of lichens, against 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral squamous cell carcinoma (OSCC) in the hamster model. Initially, the buccal pouch carcinogenesis was induced by administering 0.5% DMBA to the HBP (hamster buccal pouch) region about three times a week until the 10th week. Then, UA was orally treated with different concentrations (25, 50, 100 mg/kg b.wt) on alternative days of DMBA exposure, and the experimental process ended in the 16th week. After animal experimentation, we observed 100% tumor incidence with well-differentiated OSCC, dysplasia, and hyperplasia lesions in the DMBA-induced HBP region. Furthermore, the UA treatment of DMBA-induced hamster effectively inhibited tumor growth. In addition, UA upregulated antioxidant levels, interfered with the elevated lipid peroxidation by-product of thiobarbituric acid reactive substances, and changed the activities of the liver detoxification enzyme (Phase I and II) in DMBA-induced hamsters. Furthermore, immunohistochemical staining of inflammatory markers (iNOS and COX-2) and proliferative cell markers (cyclin-D1 and PCNA) were upregulated in the buccal pouch part of hamster animals induced with DMBA. Notably, the oral administration of UA significantly suppressed these markers during DMBA-induced hamsters. Collectively, our findings revealed that UA exhibits antioxidant, anti-inflammatory, antitumor, and apoptosis-inducing characteristics, demonstrating UA's protective properties against DMBA-induced HBP carcinogenesis.