Antioxidant and antiapoptotic activities of idoxifene and estradiol in hepatic fibrosis in rats
Introduction
Parenchymal cell membrane damage could result in the release of oxygen-derived free radicals and other reactive oxygen species (ROS) derived from lipid peroxidative processes, which represent a general feature of sustained inflammatory response and liver injury, leading to apoptosis and necrosis (Houglum et al., 1990). Fortunately, cells possess antioxidant protective mechanisms, including enzymatic defense molecules such as superoxide dismutase (SOD) and glutathione peroxidase (GPx), which can react with ROS and neutralize them before inflict damage on vital components. There is large body of evidence that in humans and animals oxidative stress is implicated in chronic liver disease and serves as a link between hepatic injury and fibrosis Shimizu, 2001, Shimizu, 2003 It should be noted that estradiol (E2) is a potent endogenous antioxidant, which reduces lipid peroxide levels in liver and serum Yoshino et al., 1987, Lacort et al., 1995. We have already reported that E2 suppressed hepatic fibrosis in rat models of hepatic fibrosis induced with pig serum and dimethylnitrosamine (DMN) Shimizu et al., 1999a, Shimizu et al., 1999b, Yasuda et al., 1999, and attenuated iron-induced lipid peroxidation in rat liver mitochondria (Omoya et al., 2001). It is well known that overexpression of Bcl-2 suppresses lipid peroxidation (Hockenbery et al., 1993), prevents apoptosis and is up-regulated by estrogen in several tissues Wang and Phang, 1995, Garcia-Segura et al., 1998, Gohel et al., 1999 Bcl-2, Bcl-XL, Bad, and Bax are members of the Bcl-2 family proteins that play an important role in regulating cell survival and apoptosis. In addition to Bcl-2, Bcl-XL also prevents apoptosis in response to a wide variety of stimuli. Conversely, proapoptotic proteins, Bad and Bax can accelerate death and in some instances are sufficient to cause apoptosis. The effects of E2 on the SOD and GPx production and the Bcl-2 family protein expression in the liver, however, remain to be elucidated.
It should be pointed out that the administration of estrogen per se in women poses some potential risks including breast cancer and endometrial abnormalities (Collaborative Group on Hormonal Factors in Breast Cancer, 1997). Idoxifene is a tissue-specific selective estrogen receptor modulator (Omoya et al., 2001), which acts in breast tissue as an estrogen antagonist through the same estrogen receptor element as the natural steroid hormone. Idoxifene acts in bone as an estrogen agonist for osteoblasts, and shows negligible agonist activity in human endometrial cells (Nuttall et al., 1998). Idoxifene was originally developed for the treatment of advanced breast cancer and the prevention of postmenopausal osteoporosis. Our recent report suggests that idoxifene and E2 protect hepatocytes from inflammatory cell injury by inhibiting activation of the nuclear factor (NF)-κB proinflammatory transcription factor (Omoya et al., 2001). However, little information is available relative to the antioxidant and antiapoptotic role of idoxifene as well as E2 in the liver.
The present study was undertaken to explore the antioxidant and antiapoptotic role of idoxifene in the DMN-induced fibrotic liver in direct comparison to the natural hormone E2. In this study, in addition to their antifibrogenic role, idoxifene and E2 suppressed DMN-mediated necrosis, lipid peroxidation, the loss of SOD and GPx production, and downregulation of Bcl-2 and Bcl-XL expression and upregulation of Bad expression in the liver.
Section snippets
Preparation of animals
Adult male Wistar rats weighing about 200 g were used for the DMN model of hepatic fibrosis. The animals (n=6 in each group), which comprised groups 2 through 6 were administered a single intraperitoneal injection of 40 mg/kg DMN (Sigma, St. Louis, MO), diluted with saline Shimizu et al., 1999a, Shimizu et al., 1999b, Yasuda et al., 1999. The controls in group 1 (n=6) received a single dose of saline. The rats in groups 4, 5, and 6 received daily oral gavage of idoxifene, which was provided by
Effects of idoxifene and E2 on hepatic necrosis, serum E2 levels, and body weights in the animal model of hepatic fibrosis
When animals were given a single injection of 40 mg/kg DMN, serum LDH levels and hepatic MDA levels increased rapidly for 3 days. Serum LDH levels normalized after 14 days, and hepatic MDA levels remained significantly higher than control values for 14 days. The serum LDH level on day 3 after DMN treatment was 5.8 times the initial value of 367 ± 49 U/L (Table 1). Hepatic collagen contents gradually rose, remaining significantly higher than control values for 14 days.
Histological examination of
Discussion
It is conceivable that cellular damage, leading to apoptosis and necrosis, might be attributed to the presence of oxygen-derived free radicals and other ROS, which are by-products of the inflammatory response. Whereas cells are well equipped to neutralized the effects of ROS, by means of a series of antioxidant protective systems. Our preliminary studies have showed that idoxifene and E2 are able to inhibit ROS generation and lipid peroxidation (Inoue et al., 2003) and inactivate NF-κB (Omoya
References (30)
- et al.
Fas enhances fibrogenesis in the bile duct ligated mouse: a link between apoptosis and fibrosis
Gastroenterology
(2002) - et al.
Bcl-2 functions in an antioxidant pathway to prevent apoptosis
Cell
(1993) - et al.
Ca2+-calmodulin antagonist chlorpromazine and poly(ADP-ribose) polymerase modulators 4-aminobenzamide and nicotinamide influence hepatic expression of BCL-XL and p53 and protect against acetaminophen- induced programmed and unprogrammed cell death in mice
Free Radical Biology Medicine
(2001) - et al.
An evaluation of the novel selective estrogen receptor modulator, idoxifene, for effects on reproduction in rats and rabbits
Toxicological Sciences
(1998) - et al.
Hepatic stellate cells contain the functional estrogen receptor β but not the estrogen receptor α in male and female rats
Biochemical Biophysical Research Communications
(2001) - et al.
Regulatory effects of testosterone and 17 beta-oestradiol on the metabolism of dimethylnitrosamine by renal and hepatic microsomal enzymes from BALB/c mice
Cytobios
(1988) Breast cancer and hormone replacement therapy: collaborative reanalysis of data from 51 epidemiological studies of 52705 women with breast cancer and 108411 women without breast cancer
Lancet
(1997)- et al.
Estradiol upregulates Bcl-2 expression in adult brain neurons
Neuroreport
(1998) - et al.
Estrogen prevents glucocorticoid-induced apoptosis in osteoblasts in vivo and in vitro
Endocrinology
(1999) - et al.
Transformation-dependent susceptibility of rat hepatic stellate cells to apoptosis induced by soluble Fas ligand
Hepatology
(1998)
Major difference in the hepatocarcinogenicity and DNA adduct forming ability between toremifene and tamoxifen in female Crl:CD(BR) rats
Cancer Research
Malondialdehyde and 4-hydroxynonenal protein adducts in plasma and liver of rats with iron overload
Journal of Clinical Investigation
Idoxifene and estradiol enhance antiapoptotic activity through the estrogen receptor β in cultured rat hepatocytes
Digestive Disease and Science
Idoxifene antagonizes estradiol-dependent MCF-7 breast cancer xenograft growth through sustained induction of apoptosis
Cancer Research
Hepatocytes in the bile duct-ligated rat express Bcl-2
American Journal of Physiology
Cited by (72)
Estrogen as a key regulator of energy homeostasis and metabolic health
2022, Biomedicine and PharmacotherapyCitation Excerpt :According to experimental studies, AR signaling has been linked to fibrogenesis and carcinogenesis by inducing reactive oxygen species [182], hepatic macrophage infiltration [184], and inducing prooncogenic transforming growth factor-beta 1 (TGF-β1) [185]. This is while, according to experimental studies in male animals, ER signaling has been linked to decreased collagen deposition in the liver [186], suppressing reactive oxygen species and mitogen-activated protein kinase (MAPK) signaling, reducing TGF-β1 expression [187], nuclear factor kappa B (NF-κB) signaling and IL-6 secretion from hepatic Kupffer cells [188], as well as increased Bcl-2 factor as a survival factor [189], thus confirming the potential anti-fibrotic/carcinogenic ER signaling in males (Table 1). In female mice, ovariectomy induces hepatic steatosis and insulin resistance [190].
Estrogen receptor agonists protect against acetaminophen-induced hepatorenal toxicity in rats
2020, Life SciencesCitation Excerpt :Despite that the majority of acetaminophen overdose cases were women, and more of the women has needed critical care and presented with an increased risk of hepatic encephalopathy with respect to male patients [13], experimental studies have demonstrated that treatment with estradiol reduced oxidative hepatic damage and increased survival rate in APAP toxicity [24]. In other models of hepatic injury, estradiol was also reported to suppress lipid peroxidation and ROM production, preserve the antioxidant enzymes [22,59–61] and inhibit hepatic fibrosis [62]. In our study, depleted hepatic GSH stores in APAP-overdosed OVX-rats were replenished when they were pretreated with either ERα or ERβ agonist, while the non-specific ER agonist E2 did not demonstrate an anti-oxidant action against APAP hepatotoxicity.
Cholestasis, Contraceptives, and Free Radicals
2017, Liver Pathophysiology: Therapies and AntioxidantsSex-specific association of estrogen receptor 2 polymorphisms with hepatitis C virus infection outcomes in a high-risk Chinese Han population
2014, Infection, Genetics and EvolutionImmunomodulatory effects by oral contraceptives in normal and cholestatic female rats: Role of cytokines
2014, International ImmunopharmacologyCitation Excerpt :Notwithstanding the enhancement of LP, collagen content and cirrhosis degree by estradiol on thioacetamide-induced liver damage [89], many reports have showed that combined OC, estradiol and ethinylestradiol suppress collagen synthesis in diverse organs in a dose-dependent manner, either in vitro or in women [90–92] by modulating the TGF-β/Smad-2 transcription factor signaling pathway [93,94]. As well, estradiol has diminished the collagen synthesis, TGF-β production and oxidative stress in diverse liver damage models in rat [95–99]. Estrogens may blunt the fibrosis process by a plausible via, the inhibition on the activation of transcription factors by suppressing oxidative stress and the mitogen activated protein kinase (MAPK) pathways, also inactivates the downstream transcription process involved in TGF-β1 expression and the HSC activation, whereas progestins act in opposition to those favorable effects [100,101].
Platycodi Radix attenuates dimethylnitrosamine-induced liver fibrosis in rats by inducing Nrf2-mediated antioxidant enzymes
2013, Food and Chemical ToxicologyCitation Excerpt :Oxidative stress, which favors mitochondrial permeability transition, promotes hepatocyte injury. Chronic DMN treatment induces hepatocyte damage through increased generation of oxidative stress (Lu et al., 2004; Shimizu et al., 1999). We previously reported that DMN increases COX-2 expression via transcription factor activation, including NF-κB (Hwang et al., 2011).
- 1
Present address: Department of Anatomy, Nantong Medical College, Nantong 226001, P.R. China.