Impact of Acetazolamide, a Carbonic Anhydrase Inhibitor, on the Development of Intestinal Polyps in Min Mice.

Colorectal cancer is a common cancer worldwide. Carbonic anhydrase (CA) catalyzes the reversible conversion of carbon dioxide to bicarbonate ion and a proton, and its inhibitor is reported to reduce cancer cell proliferation and induce apoptosis. Therefore, we asked whether acetazolamide, a CA inhibitor, could inhibit intestinal carcinogenesis. Five-week-old male Apc-mutant mice, Min mice, were fed a AIN-76A diet containing 200 or 400 ppm acetazolamide. As a result, acetazolamide treatment reduced the total number of intestinal polyps by up to 50% compared to the control group. In addition, the acetazolamide-treated group had low cell proliferation and a high apoptosis ratio in the intestinal polyp epithelial cells. Moreover, the mRNA expression level of proinflammatory cytokines, such as IL-6, involved in the cell proliferation was decreased in the polyp part of the acetazolamide-treated group. Next, we examined the effects of acetazolamide on the activation of several transcriptional factors (AP-1, HIF, HSF, NF-κB, NRF2, p53, and STAT3) using a reporter gene assay in human colon cancer cells, Caco-2 cells. Among the examined transcriptional factors, NRF2 transcriptional activation was strongly induced. NRF2-targeting genes, γGCS, GPx1, HO-1, and NQO-1, were also elevated in the intestinal polyps of acetazolamide-treated Min mice. Our results suggested that CA is involved in intestinal carcinogenesis. Acetazolamide could inhibit polyp formation through suppressing local/general cytokine levels, i.e., IL-6, via NRF2 activation.

Sesamol suppresses cyclooxygenase-2 transcriptional activity in colon cancer cells and modifies intestinal polyp development in Apc (Min/+) mice.

Excessive prostaglandin production by cyclooxygenase-2 in stromal and epithelial cells is a causative factor of colorectal carcinogenesis. Thus, compounds which inhibit cyclooxygenase-2 transcriptional activity in colon epithelial cells could be candidates for anti-carcinogenic agents. A cyclooxygenase-2 transcriptional activity in the human colon cancer cell line DLD-1 has been measured using a ß-galactosidase reporter gene system. Using this system, we demonstrated that the decrease in basal cyclooxygenase-2 transcriptional activities at 100 µM sesamol, one of the lignans in sesame seeds, was 50%. Other compounds in sesame seeds such as sesamin, sesamolin, ferulic acid, and syringic acid did not exhibit significant suppression of cyclooxygenase-2 transcriptional activity at up to 100 µM. In a following experiment, 6-week-old male Min mice, Apc-deficient mice, were divided into a non-treated and 500 ppm sesamol groups. At the age of 15 weeks, it was found that treatment with sesamol decreased the number of polyps in the middle part of small intestine to 66.1% of the untreated value. Moreover, sesamol suppressed cyclooxygenase-2 and cytosolic prostaglandin E2 synthase mRNA in the polyp parts. The present findings may demonstrate the novel anti-carcinogenetic property of sesamol, and imply that agents that can suppress cyclooxygenase-2 expression may be useful cancer chemopreventive agents.

Novel compound SK-1009 suppresses interleukin-6 expression through modulation of activation of nuclear factor-kappaB pathway.

Although interleukin-6 (IL-6) is an important biological mediator playing an indispensable role in inflammation and cancer, few inhibitors and suppressors are known. In the present study, the underlying mechanisms of a novel chemically synthesized compound SK-1009, which has suppressive properties on IL-6 production in human macrophage cells, were examined. SK-1009 suppressed IL-6 mRNA levels in human colon cancer cells. Thus, the influence of SK-1009 on transcription factor, nuclear factor-kappaB (NF-κB), which is involved in expression of the IL-6 gene was assessed. SK-1009 was found to suppress degradation of I-κB, an NF-κB inhibitory factor, and consequently inhibited the NF-κB activation pathway. The inhibitory property was almost the same as other NF-κB inhibitors, such as 5HPP-33. Thus, SK-1009 exerts a potent inhibitory effect on IL-6 expression, apparently mediated by modulation of activation of NF-κB transcription factor.

Bi-directional regulation between adiponectin and plasminogen activator-inhibitor-1 in 3T3-L1 cells.

BACKGROUND: Adiponectin (APN) and plasminogen activator inhibitor-1 (Pai-1) are adipocytokines, and low levels of serum APN and high levels of PAI-1 are observed in obese patients. Moreover, both APN and Pai-1 are known to be involved in colorectal carcinogenesis. Recently, we demonstrated that serum Pai-1 levels are elevated in APN-deficient mice. We hypothesized that Pai-1 expression levels could be depressed by APN. Thus, we aimed to clarify the bi-directional regulatory mechanisms between APN and Pai-1. MATERIALS AND METHODS: We investigated the expression levels of APN and Pai-1 during 3T3-L1 pre-adipocyte differentiation, and examined the role of AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor (PPAR)-γ on APN and Pai-1 expression at early and late differentiation stages. RESULTS: In the early phase of differentiation, Pai-1 expression increased and APN slightly decreased. Reduction of Pai-1 or activation of PPARγ resulted in elevation of APN, and supplementation of APN with activation of AMPK resulted in reduction of Pai-1. In the late phase of differentiation, APN increased its expression and Pai-1 decreased. Supplementation of Pai-1 resulted in a slight reduction of APN. CONCLUSION: It is suggested that APN and Pai-1 expressions are inversely-regulated. Understanding of the regulatory system between APN and Pai-1 may lead to finding novel methods for colorectal cancer prevention.