Houttuynia cordata Extract Ameliorates Bladder Damage and Improves Bladder Symptoms via Anti‐Inflammatory Effect in Rats with Interstitial Cystitis

The mechanism of interstitial cystitis/bladder pain syndrome (IC/BPS) remains unclear to date, but reports showed that bladder inflammation and increasing number of activating mast cells in bladder tissues were common in patients with IC/BPS. Houttuynia cordata is widely used in Chinese traditional medicine, and its function of anti-inflammation has been proved. The purpose of this study was to investigate the efficacy and possible mechanisms of the Houttuynia cordata (HC) extract in the treatment of interstitial cystitis/bladder pain syndrome (IC/BPS). In the current study, a total of 30 adult female rats were randomly divided into three groups: sham group (n = 10), cyclophosphamide + saline (CYP + NS) group (n = 10), and cyclophosphamide + Houttuynia cordata extract (CYP + HC) group (n = 10). The animal model of IC/BPS was induced with cyclophosphamide (75 mg/kg, intraperitoneal injection, once every 3 days for 10 days) in the CYP + NS group and CYP + HC group, and sham rats received a volume-matched injection of saline. After anesthesia with urethane (0.8 g/kg, intraperitoneal injection), intravesical administration of either saline (1 ml) or Houttuynia cordata extract (1 ml, 2 g/ml) was continued once per day for a week in the CYP + NS group and CYP + HC group, respectively. Subsequently, urinary frequency, nociceptive behaviors, cystometry, bladder weight, histological changes, and cytokine (IL-6, IL-8, TNF-α) concentration were evaluated and compared among the three groups. Variables including inflammatory grade, mast cell number, proportion of activated mast cells, bladder weight, cytokine concentration of bladder homogenates, and frequency of urination significantly increased in the CYP + NS group compared with the sham group (P < 0.01) and CYP + HC group (P < 0.01). Besides, compared with the CYP + NS group, longer intercontraction interval, bigger bladder capacity, higher nociceptive threshold, fewer number of mast cells, and lower proportion of activated mast cells were found in the CYP + HC group (P < 0.01). Our study demonstrated that the Houttuynia cordata extract can effectively inhibit mast cell proliferation and activation and downregulate proinflammatory cytokine in a rat model of IC/BPS induced with cyclophosphamide and might be potentially valuable for the treatment of IC/BPS.