St. John's wort attenuates irinotecan-induced diarrhea via down-regulation of intestinal pro-inflammatory cytokines and inhibition of intestinal epithelial apoptosis

Abstract

Diarrhea is a common dose-limiting toxicity associated with cancer chemotherapy, in particular for drugs such as irinotecan (CPT-11), 5-fluouracil, oxaliplatin, capecitabine and raltitrexed. St. John's wort (Hypericum perforatum, SJW) has anti-inflammatory activity, and our preliminary study in the rat and a pilot study in cancer patients found that treatment of SJW alleviated irinotecan-induced diarrhea. In the present study, we investigated whether SJW modulated various pro-inflammatory cytokines including interleukins (IL-1β, IL-2, IL-6), interferon (IFN-γ) and tumor necrosis factor-α (TNF-α) and intestinal epithelium apoptosis in rats. The rats were treated with irinotecan at 60 mg/kg for 4 days in combination with oral SJW or SJW-free control vehicle at 400 mg/kg for 8 days. Diarrhea, tissue damage, body weight loss, various cytokines including IL-1β, IL-2, IL-6, IFN-γ and TNF-α and intestinal epithelial apoptosis were monitored over 11 days. Our studies demonstrated that combined SJW markedly reduced CPT-11-induced diarrhea and intestinal lesions. The production of pro-inflammatory cytokines such as IL-1β, IFN-γ and TNF-α was significantly up-regulated in intestine. In the mean time, combined SJW significantly suppressed the intestinal epithelial apoptosis induced by CPT-11 over days 5–11. In particular, combination of SJW significantly inhibited the expression of TNF-α mRNA in the intestine over days 5–11. In conclusion, inhibition of pro-inflammatory cytokines and intestinal epithelium apoptosis partly explained the protective effect of SJW against the intestinal toxicities induced by irinotecan. Further studies are warranted to explore the potential for STW as an agent in combination with chemotherapeutic drugs to lower their dose-limiting toxicities.

Introduction

St. John's wort (Hypericum perforatum, SJW) is one of the most commonly used herbal medicines for the treatment of mild to moderate depression (Di Carlo et al., 2001). SJW is also used as an antihypertensive and mild anti-inflammatory agent. SJW contains over two dozens of constituents, among which hyperforin, hypericin and quercetin are the major active components. Hyperforin is potent reuptake inhibitor of serotonin, dopamine, noradrenaline and γ-amino-n-butyric acid, contributing to the antidepressant activity of SJW (Di Carlo et al., 2001). In contrast to the large number of reports on the antidepressive effects of SJW, data on the molecular basis of its anti-inflammatory action are scanty. Several in vitro and animal studies revealed that SJW had anti-inflammatory activity (Fiebich et al., 2001, Tedeschi et al., 2003, Gobbi et al., 2004). The anti-inflammatory effects of SJW or its ingredients have been attributed to the inhibition of nuclear factor-κB activation, protein kinase C, the signal transducer and activator of transcription-1α (STAT-1α) and inducible nitric-oxide synthase (Tedeschi et al., 2003). SJW extracts also inhibited substance P-induced interleukin (IL)-6 production in a dose-dependent manner in human astrocytoma cells (Fiebich et al., 2001), and a study in IL-6 knockout mice indicated that IL-6 was necessary to the antidepressant action of SJW through activation of the serotonin system (Calapai et al., 2001). Cytokines have been implicated in the onset and maintenance of depressive disorders (Dunn et al., 2005).

Cytokines are relatively small molecular weight polypeptides released by all nucleated cell types in the body that have specific effects on the interactions and communications between cells or on the behavior of cells. Cytokines mainly include the interleukins (ILs), lymphokines and cell signal molecules, such as tumor necrosis factor (TNF)-α and the interferon (IFN). The majority of cytokines are pleiotropic in their functional activities, and they are extracellular signaling molecules essential to host development and maturation, immune and inflammatory responses and tissue repair processes (Gura, 1996). Cytokines are highly inducible molecules with short half-lives during immunological reactions and inflammatory conditions. TNF-α, IL-1β, IL-6, IL-12 and IFN-γ are cytokines that exert predominantly pro-inflammatory effects in vitro and in vivo, among which IL-6 can also exert anti-inflammatory effect, depending on cell type and the specific physiologic (e.g. age and genetic factors) and pathologic (e.g. disease severity) state (Kishimoto et al., 1992). All these cytokines play a critical role in inflammatory diseases.

Diarrhea is a common dose-limiting toxicity associated with cancer chemotherapy, especially in treatment of colorectal cancer by use of irinotecan (CPT-11), 5-fluouracil, oxaliplatin, capecitabine or raltitrexed (Sharma et al., 2005). These chemotherapeutic agents were associated with diarrhea in 50–80% of patients when used alone or in combination in randomized phase III trials. The incidence of grade 3 or 4 diarrhea was up to 40% of patients with use of irinotecan (Rothenberg et al., 1996). Severe diarrhea causes dehydration, renal failure and thromboembolic events. Furthermore, diarrhea combined with severe neutropenia commonly leads to Gram-negative sepsis, and such complications have contributed to the high incidence of mortality for patients who received irinotecan-based regimens. The mechanisms for anticancer drug-induced diarrhea are unclear, but it appears to be associated with intestinal exposure to these drugs which induce epithelial apoptosis characterized by the generation of DNA fragments through the action of endogenous endonucleases (Thompson, 1995). A number of cytotoxic drugs cause severe intestinal inflammatory damage with hypersecretion of pro-inflammatory cytokines.

Invariably, high-dose loperamide is recommended to manage irinotecan-induced diarrhea, consisting of an initial dose of 4 mg followed by 2 mg every 2 h until there has been 12 h without loose motions (Benson et al., 2004). However, a number of patients do not respond to this agent. Therefore, new and effective agents are needed to alleviate irinotecan-induced diarrhea. Our preliminary study in the rat clearly demonstrated that pretreatment with SJW significantly reduced the diarrhea induced by use of irinotecan (Hu et al., 2005). Interestingly, a recent pilot study in 5 cancer patients found that oral treatment of SJW at 900 mg/day for 18 days alleviated irinotecan-induced diarrhea (Mathijssen et al., 2002). However, the mechanism for this is unknown. In the present study, we tested the hypothesis that the inhibition of pro-inflammatory cytokines and intestinal epithelium apoptosis contributed to the protective effects of SJW against the intestinal toxicity of irinotecan. Our data indicate that SJW efficiently inhibited the intestinal inflammation induced by irinotecan accompanied with a reduction in pro-inflammatory cytokines and intestinal epithelium apoptosis.