Pepstatin A

The core pathological mechanism of gastric ulcer is the damage of gastric mucosal defense barrier and the imbalance of gastric acid/pepsin digestion. Pepsin is secreted by the main cells of the stomach and activated as pepsin in the environment of gastric acid (pH<4). The latter can degrade proteins in food, but excessive activation can also digest the gastric mucosa itself, leading to ulcer formation. Research has shown that the activity of gastric protease is positively correlated with the severity of ulcers, and inhibiting its activity is one of the key strategies for treating gastric ulcers. It has extremely strong inhibitory activity against gastric protease, with an IC50 value of only 4.5 nM. Rat experiments have shown that oral administration of Pepstatin (0.5-50 mg/kg) can significantly reduce the incidence of pyloric ligation ulcers, and its mechanism is related to direct inhibition of gastric protease activity and reduction of gastric acid damage to gastric mucosa.

Further research has confirmed that Pepstatin can maintain the barrier function of gastric mucosal epithelial cells by inhibiting the degradation of tight junction proteins (such as occludin and claudin) mediated by gastric protease, thereby reducing mucosal damage caused by gastric acid reflux. Although Pepstatin has shown good anti ulcer effects in animal models, its clinical application still faces challenges. On the one hand, the oral bioavailability of natural Pepstatin is relatively low, and its stability and absorption rate need to be improved through structural modification or nano formulation technology; On the other hand, long-term use may inhibit digestive function, and the efficacy and safety need to be balanced. Currently, Pepstatin is more commonly used as a research tool to explore the mechanisms of gastric ulcers, rather than directly as a clinical drug.

GERD is a chronic disease caused by the reflux of gastric contents into the esophagus, leading to symptoms such as heartburn and acid reflux. Gastric acid (pH<2) is the main damaging factor for reflux, but when activated in an acidic environment, gastric protease can break down the mucosal barrier by degrading tight junction proteins and glycoproteins in the esophageal mucosa, leading to deep tissue damage. Research has shown that gastric protease activity is closely related to the severity of GERD and the risk of complications such as Barrett's esophagus. The study in Gastroenterology utilized acetylgastrin (Pepstatin analog) to specifically inhibit gastric protease activity, confirming that gastric protease reflux to the esophageal mucosa can break down the mucosal barrier by degrading occludin and claudin.

Pepstatin A can reduce the damage of reflux to esophageal mucosa and promote mucosal repair by inhibiting gastric protease. In addition, Pepstatin can also inhibit reflux induced apoptosis of esophageal epithelial cells, further protecting mucosal integrity. At present, the standard treatment for GERD is proton pump inhibitors (PPIs), but some patients have poor response to PPIs or develop resistance. The combination of Pepstatin A and PPI may enhance therapeutic efficacy through a dual mechanism of inhibiting gastric acid secretion and blocking gastric protease activity, especially for patients with refractory GERD. In addition, local administration of Pepstatin (such as esophageal gel) can reduce systemic side effects and improve treatment compliance.

The pathological features of IBD (including Crohn's disease and ulcerative colitis) are abnormal activation of intestinal mucosal immunity and chronic inflammation. Cathepsin D is an aspartic protease that is upregulated in the intestinal mucosa of IBD patients. It exacerbates intestinal inflammation and tissue damage by promoting the release of pro-inflammatory cytokines (such as IL-6, TNF - α) and apoptosis of intestinal epithelial cells. Pepstatin can specifically inhibit the activity of protease D, thereby blocking its pro-inflammatory effect. Animal experiments have shown that Pepstatin treatment can alleviate intestinal inflammation in DSS induced colitis model mice, manifested by reduced colon length, decreased histological damage scores, and decreased levels of pro-inflammatory cytokines. The mechanism may be related to the inhibition of NF - κ B signaling pathway activation and the reduction of intestinal epithelial cell apoptosis.

Cathepsin D is overexpressed in various digestive tract tumors, such as gastric cancer and colorectal cancer. It promotes tumor cell invasion and metastasis by degrading extracellular matrix proteins, such as collagen and laminin. In addition, protease D can activate pro angiogenic factors (such as VEGF) to promote tumor angiogenesis. Pepstatin can block the invasion and metastasis of tumor cells by inhibiting the activity of protease D. For example, in the breast cancer model, Pepstatin treatment can significantly reduce the number of lung metastases; In colorectal cancer models, it can inhibit tumor growth and angiogenesis. In addition, Pepstatin can exert anti-tumor effects by inducing tumor cell apoptosis (such as upregulating Bax/Bcl-2 ratio) and inhibiting autophagy (blocking lysosomal degradation pathway in combination with E-64d).

The combination of Pepstatin with chemotherapy drugs such as 5-FU and oxaliplatin may enhance anti-tumor efficacy through synergistic effects. But it is necessary to ensure that Pepstatin only inhibits tumor associated aspartic protease and does not affect normal cell function; Long term use may lead to tumor cells bypassing inhibition by upregulating other proteases, such as matrix metalloproteinases; Targeted delivery systems (such as nanoparticles and antibody conjugated drugs) need to be developed to increase drug concentration in tumor tissues.