A Survey of Therapeutic Effects of Artemisia capillaris in Liver Diseases

Artemisia capillaris has been recognized as an herb with therapeutic efficacy in liver diseases and widely used as an alternative therapy in Asia. Numerous studies have reported the antisteatotic, antioxidant, anti-inflammatory, choleretic, antiviral, antifibrotic, and antitumor activities of A. capillaris. These reports support its therapeutic potential in various liver diseases such as chronic hepatitis B virus (HBV) infection, cirrhosis, and hepatocellular carcinoma. In addition, several properties of its various constituents, which provide clues to the underlying mechanisms of its therapeutic effects, have been studied. This review describes the scientific evidence supporting the therapeutic potential of A. capillaris and its constituents in various liver diseases.


Introduction
The liver plays a vital role in the metabolic maintenance of homeostasis and toxic excretion of endogenous and exogenous metabolites such as those associated with drugs, alcohols, viral and fungal infections, and various noxious materials [1]. Because of this important hepatic function, liver impairment can induce the development of a variety of pathological and clinical conditions such as hepatic steatosis, inflammation, fibrotic change, and tumors. Although a considerable number of conventional medicines have been used for liver dysfunction, unanticipated side effects such as hepatic or renal toxicity, intolerance to drugs, and poor treatment occur in clinical settings. These limitations have led to the search for alternative remedies among the various herbal formulas. These herbal remedies have existed for a long time and have been useful in the management of hepatic diseases, and A. capillaris is one of the medicinal herbs that are frequently used for liver diseases [2,3].
Despite the various medicinal applications that have been suggested for A. capillaris through a large number of surveys, there has been no review article that provides useful information with a well-organized collation of the pharmacological effects of A. capillaris and its compounds. Therefore, to meet this need, we researched a wide range of studies on therapeutic activities of A. capillaris and its constituents in liver diseases. In addition, we arranged these results based on the key activities that occur during the pathological developmental stages from liver dysfunction to hepatocarcinogenesis ( Figure 1).

Therapeutic Effects of A. capillaris
For a variety of activities from A. capillaris relevant to liver diseases, we organized various therapeutic effects that have been reported for this plant according to each pathological step from oxidative stress to carcinogenesis (Table 1).

Antioxidant Effects.
The liver is very susceptible to oxidative stress and plays an important role in controlling the balance between the antioxidant defense system and enhanced oxidative stress [30]. Excessive production of deleterious reactive oxygen species (ROS) could lead to liver dysfunction symptoms such as steatosis [17], alcoholic degeneration [19], cholestasis [18], and fibrosis [16] as a result of hepatocellular damage. Therefore, many studies related to the antioxidant effects of A. capillaris in hepatotoxicity have been conducted using chemical toxins, alcohol, fatty acids, bile duct ligation, and so forth. Oxidative injury to the liver can be confirmed by monitoring the malondialdehyde (MDA), which represents lipid peroxidative products. A. capillaris has been shown to significantly reduce the MDA content in the liver of rats with bile duct ligation ( < 0.5) [18] and 50 and 100 mg/kg of its water extract notably decreased serum levels of MDA in alcohol-pyrazole-fed rats [19]. A. capillaris was also revealed to restore significantly reduced levels of antioxidant enzymes including superoxide dismutase (SOD), glutathione (GSH), GSH-peroxidase (Px), GSH-reductase (Rd), and catalases (CAT) under conditions of oxidative stress in in vivo rat models [17][18][19]. Furthermore, the antioxidant potential of A. capillaris was shown to extend to liver fibrosis [18] and hepatoprotection [16,17,19,30] by observing hydroxyproline, a mark of an increase in collagen synthesis and liver function enzymes including aspartate transaminase (AST) and alanine transaminase (ALT). Therefore, A. capillaris is a possible candidate agent for use in the reduction of oxidative toxicities and for hepatoprotection and in liver function recovery.

Antisteatotic Effect.
The hepatic accumulation of lipids, a characteristic feature of fatty liver disease and steatohepatitis, is strongly associated with insulin resistance [31], fibrogenic activities [32], oxidative stress [33], and lipoapoptosis [13]. Therefore, alternative therapeutic options with antisteatotic activities which can prevent oxidative and apoptotic changes in liver induced by lipids are desirable. A. capillaris was reported to markedly decrease the accumulated fat volume in free fatty acid-treated HepG2 cells and 3T3-L1 adipocytes [13,14]. A. capillaris also conspicuously improved the lipid profile including the triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) levels in obese rats [20]. These antilipidemic activities of A. capillaris can be attributed to its inhibition of apoptosis via the deactivation of phosphorylated (p) c-Jun N-terminal kinases (JNK) [13] or the increase in mitochondrialoxidation [14], but more studies are needed to apply it as one of the lipid-lowering agents.

Anti-Inflammatory Effects.
Chronic inflammatory responses in the liver are often induced by viral infection, alcohol abuse, fat accumulation, and toxic agents. Chronic inflammation causes pathological changes in liver function and, therefore, might progress to severe problems such as liver cirrhosis or cancer [34]. For this reason, controlling acute or chronic inflammation is desirable in liver disease management. Studies identifying the anti-inflammatory effect of A. capillaris have mainly been conducted by evaluating the levels of inflammatory cytokines. For instance, the aqueous extract of A. capillaris decreased the production of tumor necrosis factor-(TNF-) by deactivating nuclear factor kappa-light-chain enhancer of activated B-cells (NF-B) in both lipopolysaccharide-(LPS-) and ethanol-treated HepG2 cells [21,22]. A. capillaris also suppressed secretion of proinflammatory cytokines such as interleukin-(IL-) 1 , IL-1 , IL-6, and IL-8 from HepG2, RAW 264.7 cells, and rat liver [6,22,35]. In addition, cyclooxygenase-(COX-) 2 and nitric oxide were downregulated in HepG2, RAW 264.7, RGM-1, rat insulinoma, splenocytes, and liver cells [6, 21-23, 35, 36]. These immunosuppressive effects of A. capillaris can be beneficial for various kinds of inflammatory conditions that occur in the liver.

Antiviral
Effects. Viral hepatitis has the propensity to progress and possibly aggravate to liver cirrhosis or hepatocellular carcinoma. It has been revealed as a serious public  health problem that affects people worldwide. Despite the available conventional therapies such as nucleoside and nucleotide analogues or interferon, these agents are fraught with challenging limitations including toxicity, drug resistance, recurrence, and unsatisfactory treatment outcomes [18,25,37,38]. Traditional herbal medicines, therefore, like Rheum palmatum, Scutellaria baicalensis, and Salvia miltiorrhiza, have also been used for the treatment of hepatitis B virus (HBV) infections [38]. In particular, previous investigations suggested that the antiviral effects of A. capillaris were attribu-  [24]. In addition, a recent study revealed that the compound 2f, which is a derivative of p-hydroxyacetophenone from A. capillaris, showed inhibitory effects with IC 50 of 5.8 M and SI of 160.3 against HBV DNA replication [25]. Consequently, A. capillaris, which contained components with antiviral activity, was thought to be an adequate therapeutic candidate for the control of viral infections of the liver, although previous studies of this plant were mostly limited to HBV infections.

Choleretic Effects.
Jaundice which is one of the symptoms induced by cholestasis turns skin, conjunctival membranes, and urine yellowish and is frequently seen in liver diseases such as hepatitis, liver cirrhosis, bile duct obstruction, and cancer. A number of studies of herbal therapies for hyperbilirubinemia have focused mainly on neonatal jaundice because of the adverse effects of drug treatment and exchange transfusions [40][41][42]. In particular, A. capillaris has been used for years in China, Japan, and Korea to alleviate jaundice and its choleretic effect and was officially implemented for use in Japan from 1981 to 1994 based on its various components [8,26,43]. Consequently, p-hydroxyacetophenone, scoparone, capillartemisin B 1 , and artepillins A and C from A. capillaris (dried flower, 50 mg/kg) were shown to increase bile flow without affecting the enterohepatic circulation or metabolism of bile acids in rat models. A significant increase in bile secretion of 169% was observed within 30 min of the administration of p-hydroxyacetophenone [26]. In addition, 3 mL of bile secretion for 6-8 h after treatment with the water extract of A. capillaris [8] might suggest the potential therapeutic benefits of A. capillaris on cholestatic liver dysfunctions.

Antifibrotic Effects.
Liver fibrosis is a healing process that occurs in damaged liver tissues and can progress to liver cirrhosis or carcinoma [7,44,45]. The accumulation of fibrotic factors like collagen-1 and -smooth muscle actin ( -SMA) Evidence-Based Complementary and Alternative Medicine 5 in the liver is attributable to hepatic stellate cells induced by the tumor growth factor-(TGF-) or platelet-derived growth factor (PDGF) [46]. However, conventional drugs that can block the progression of fibrogenesis or prevent liver fibrosis have not been developed yet. Concerning the antifibrotic effects of A. capillaris, there existed results effective against liver fibrosis in rat models. Han et al. demonstrated that 50 mg/kg dose of the water extract of A. capillaris had antihepatofibrotic effects in rats with bile duct ligation and regulated fibrogenic mediators such as -SMA, PDGF-, TGF-, collagen, type I, alpha 1 (Col1A1), and tissue inhibitor of metalloproteinases TIMP1 and TIMP2 [27]. The water extract of A. capillaris also suppressed PDGF-, TGF-, and connective tissue growth factor (CTGF), which are three major profibrotic cytokines, in a carbon tetrachloride-(CCl 4 -) induced liver fibrosis rat model. However, the statistical significance was not proven, and Artemisia iwayomogi rather than A. capillaris was more effective against the fibrotic changes [3]. The -sitosterol derived from A. capillaris administered at 120 M and 40 mg/kg significantly regulated Col1A1 and -SMA in LX2 cells and dimethylnitrosamine-(DMN-) induced fibrotic mice [7]. This effect was mediated by activating caspase-3, caspase-9, and Bcl-2-associated X protein (BAX) and inhibiting B-cell lymphoma 2 (Bcl-2), myeloid cell leukemia-(Mcl-) 1, phosphorylation of mitogen-activated protein kinase (MEK), and extracellular signal-regulated kinases (ERK) [7].

Antitumor Effects.
Primary liver cancer originating from the liver remains a serious health problem. Although the range of the geographical distribution and incidence rates are diverse with countries, gender-wise it is more prevalent in males than in females [47]. There are numerous reports on the various antitumor effects of curative treatment options like chemicals, proton, and immune therapy [48,49]. Most studies of the inhibitory effect of A. capillaris against hepatoma cells have focused on apoptotic effects. Articles in Taiwan and China reported that A. capillaris showed growth-inhibitory effects in SMMC-7721 (human hepatoma cell line), HepG2, Huh-7, HeLa, and mouse liver cells by inducing tumor cell apoptosis [29,50,51]. These results are opposed to the inhibition of TGF-1 induced apoptosis [52], but A. capillaris prevented apoptotic morphological changes of normal hepatocytes, not tumor cells in this study. Moreover, A. capillaris was also found to promote the apoptotic process in cancer cells like the human leukemia HL-60 cells or nasopharyngeal carcinoma cells (CNE-2 cells), even though they are not related to the liver [28,53]. In view of these results, intensive studies are required to expand the possible application of the antitumor effects of A. capillaris to other forms of cancer.

Medicinal Effects of Various Constituents of A. capillaris
There are a number of substances isolated from A. capillaris, which exhibit diverse medicinal effects applicable to different liver-related diseases ( Table 2). Among those bioactive constituents, 6 compounds with remarkable medicinal effects were selected and discussed (Figures 2 and 3).

Scoparone.
Scoparone, a derivative of 6,7-dimethoxycoumarin (coumarin) isolated from A. capillaris, showed antioxidant properties by reducing the MDA and ALT levels in coldreserved rat hepatocytes, thereby preventing ischemic injury induced by liver transplantation [56]. The anti-inflammatory activities of scoparone were revealed by its inhibition of the expression of IL-8, monocyte chemotactic protein-1, and NF-B subunits via I-B activation in U 937 human monocytes [75]. Therefore, scoparone could be a potential candidate for the therapy of hepatitis or biliary tract infection [57].

Isochlorogenic Acids. Isochlorogenic acids isolated from
Laggera alata significantly inhibited the expressions of HBsAg, HBeAg, and cccDNA but not HBV DNA levels and induced heme oxygenase-1, a repressor of HBV replication, in HepG2.2.15 cells [54]. This result indicates that isochlorogenic acids may act at the translational and not transcriptional step of viral proliferation [70]. In addition, they showed antiinflammatory effects, which were mediated by increasing antioxidant enzymes like SOD and GSH-Px [68,71]. Furthermore, the antitumor effect of isochlorogenic acids was investigated by inducing apoptosis in murine sarcoma 180 cells via the activation of NF-B signaling and production of nitric oxide [72].

Conclusion
A. capillaris has a wide spectrum of pharmacologically effective constituents for various liver diseases ranging from fatty liver disease to liver cancer. Our findings provided at least partial and plausible explanations of the therapeutic properties of A. capillaris that are applicable in liver diseases. In particular, various compounds isolated from A. capillaris are beneficial for treating liver diseases including scoparone, scopoletin, chlorogenic acid, isochlorogenic acid, and umbelliferone. These constituents are effective for liver dysfunctions like fatty liver. In addition, scoparone, scopoletin, isochlorogenic acid, and pumilaside A are effective for hepatitis including steatohepatitis, alcoholic hepatitis, and viral hepatitis. Furthermore, scoparone, capillartemisin, capillarisin, scopoletin, isoscopoletin, artepillin, p-hydroxyacetophenone, esculetin, and -sitosterol are effective for liver cirrhosis while scoparone, capillartemisin, capillarisin, capillin, scopoletin, isoscopoletin, artepillin, p-hydroxyacetophenone, esculetin, isochlorogenic acid, and quercetin are effective in liver cancer ( Figure 3). In addition, Yin-Chen-Hao-Tang decoction including A. capillaris significantly decreased -SMA, TGF-1 , and procollagen 1 by suppressing apoptosis in rats with hepatic fibrosis [76,77]. Therefore, studies elucidating the pharmacological effects of A. capillaris in liver diseases are required. Hence, more studies considering diverse extraction methods, experiment techniques, efficient dosage, and related metabolism are required to verify pharmacological effects of A. capillaris, its constituents, and decoction in liver diseases.