LC, a novel estrone–rhein hybrid compound, concurrently stimulates osteoprotegerin and inhibits receptor activator of NF-κB ligand (RANKL) and interleukin-6 production by human osteoblastic cells

Yue Wang; Ling Zhi Li; Yong Liang Zhang; Ya Qin Zhu; Jian Wu; Wei Jia Sun

doi:10.1016/j.mce.2011.01.018

Molecular and Cellular Endocrinology 337 (2011) 43–51

Contents lists available at ScienceDirect

Molecular and Cellular Endocrinology

journal homepage: www.elsevier.com/locate/mce

LC, a novel estrone–rhein hybrid compound, concurrently stimulates

osteoprotegerin and inhibits receptor activator of NF-␬B ligand (RANKL) and

interleukin-6 production by human osteoblastic cells

Yue Wang

a,b,∗∗

, Ling Zhi Li

b,c,∗

, Yong Liang Zhang

b

, Ya Qin Zhu

a

, Jian Wu

a

, Wei Jia Sun

a

Department of Immunology, Medical College of Chinese People’s Armed Police Forces, Tianjin, People’s Republic of China

b

TianJin Key Laboratory for Biomarkers of Occupational and Environmental Hazard, Tianjin, People’s Republic of China

c

Department of Pharmaceutical Chemistry, Medical College of Chinese People’s Armed Police Forces, Tianjin, People’s Republic of China

article info

Article history:

Received 29 October 2010

Received in revised form

31 December 2010

Accepted 25 January 2011

Keywords:

LC

OPG

RANKL

IL-6

Estrogen receptor

Osteoblast

abstract

Estrogen analogues are promising drugs for postmenopausal osteoporosis, but because of their possible

side effects such as increased risk of cancer, estrogens which exert their estrogenic effects selectively on

bone are desired. It has been shown that rhein inhibits osteoclast formation and bone resorption activity

and has an antitumor role in several types of cancers. Having found that rhein had high afﬁnity for the

bone mineral, we synthesized estrone–rhein hybrid compounds and conﬁrmed that one of these hybrid

compounds, LC, exhibited a selective proﬁle in the bone and prevented bone loss but had no effect on

endometrium growth in ovariectomized rats. However, the mechanisms underlying its actions on human

bone cells have not been well deﬁned. Here we show that LC concurrently stimulates osteoprotegerin

(OPG) and inhibits receptor activator of nuclear factor-␬B ligand (RANKL) and Interleukin-6 (IL-6) pro-

duction by human osteoblastic MG-63 cells containing two estrogen receptor (ER) isotypes. Treatment

with the ER antagonist ICI 182,780 abrogates the above actions of LC on osteoblast-derived cells. Using

small interfering double-stranded RNAs (siRNA) technology, we further demonstrate that the effects of LC

on IL-6 production are mediated by both ER␣ and ER␤ but those on OPG and RANKL expression primarily

by ER␣. Furthermore, we also demonstrate that LC functions at least partially through activation of the

classic estrogen response element (ERE) pathway as well as Ras/MEK/ERK and PI3K/Akt signaling. The

effect of LC on bone is due to not only its estrogenic activity but also action of its rhein moiety. Also, this

compound shows much weaker effect on breast epithelial cell growth than that of estrone. Therefore,

using rhein for conjugating compounds is a promising method of effectively targeting estrogens to the

bone.

1. Introduction

Estrogen replacement therapy has long been an important

therapeutic modality for the prevention and treatment of post-

menopausal osteoporosis (Eastell, 1998). However, long-term

compliance with estrogen therapy is limited, and there are increas-

ing concerns regarding its safety (Eastell, 1998; Writing Group for

the Women’s Health Initiative Investigators, 2002). At present, two

approaches can be taken to create such bone-selective estrogens.

One approach is to make estrogens that act speciﬁcally on bone

∗

Corresponding author at: Department of Pharmaceutical Chemistry, Medical

College of Chinese People’s Armed Police Forces, Hedong District Chenlin Road No.

211, Tianjin 300162, People’s Republic of China. Tel.: +86 22 60578184.

∗∗

Corresponding author at: Department of Immunology, Medical College of Chi-

nese People’s Armed Police Forces, Hedong District Chenlin Road No. 211, Tianjin

300162, People’s Republic of China. Tel.: +86 22 60578099.

E-mail addresses: wy68wy68@yahoo.com.cn (Y. Wang), llzhx@tom.com (L.Z. Li).

irrespective of their distribution, with a very weak effect on repro-

ductive tissues (Gennari et al., 2007; Kulak Júnior et al., 2010).

Examples are the so-called selective estrogen-receptor modulators

(SERMs) such as tamoxifen, raloxifene, bazedoxifene, lasofoxifene

and ospemifene (Gennari et al., 2007; Kulak Júnior et al., 2010).

These compounds function as estrogen antagonists in reproduc-

tive organs, whereas they act as estrogen agonists on bone and

lipid metabolism. The second approach is to make estrogens that

distribute speciﬁcally in bone. Examples of these are hybrids

made with tetracycline (Orme and Labroo, 1994; Neale et al.,

2009), bisphosphonate (Bauss et al., 1996; Tsushima et al., 2000),

small heterocycles (Willson et al., 1996), and acidic oligopeptide

(Yokogawa et al., 2001; Yokogawa, 2006).

To obtain a highly bone-selective estrogen that distributes in the

bone effectively, we have synthesized estrone–rhein hybrid com-

pounds (Li et al., 2004). Rhein was used because it is known to have

high afﬁnity for hydroxyapatite in the bone (Cui et al., 2008; Zhang

et al., 2008) and was suggested to function as a good carrier of estro-

doi:10.1016/j.mce.2011.01.018

LC, a novel estrone–rhein hybrid compound, concurrently stimulates osteoprotegerin and inhibits receptor activator of NF-κB ligand (RANKL) and interleukin-6 production by human osteoblastic cells

Wang, Yue; Li, Ling Zhi; Zhang, Yong Liang; Zhu, Ya Qin; Wu, Jian; Sun, Wei Jia

Follow Molecular and Cellular Endocrinology , Volume 337 (1) Elsevier – Apr 30, 2011