**3. Vitamin A and stellate cells in infammation and tumorigenesis**

#### **3.1 Decrease of vitamin A-rich stellate cells in chronic hepatitis C**

 With respect to liver disease, the number of periportal vitamin A-rich stellate cells is decreased in chronic hepatitis C patients, which is associated with aggravation of hepatitis, as indicated by elevated serum alanine aminotransferase (ALT) levels [28] (**Figure 5A**). Tis tendency was demonstrated in both vitamin A-rich and vitamin A-poor stellate cells. Additionally, the number of periportal vitamin A-rich stellate cells or of both vitamin A-rich and vitamin A-poor stellate cells combined is

### *The Role of Vitamin A-Storing Cells (Stellate Cells) in Inflammation and Tumorigenesis DOI: http://dx.doi.org/10.5772/intechopen.83523*

signifcantly decreased during the progression of chronic hepatitis C (from chronic persistent hepatitis, CPH or chronic active hepatitis, CAH2A to CAH2B) [29] (**Figure 5B**). Since vitamin A-absent stellate cells, that is, fbrotic myofbroblasts, were not counted in these studies, the change of vitamin A-storing stellate cells to myofbroblasts in chronic hepatitis was not assessed. Hepatic stellate cells in the normal human liver express both cellular retinol-binding protein-1 (CRBP-1) and αSM-actin, while myofbroblasts express only αSM-actin in fbrotic or cirrhotic liver, suggesting a change of stellate cells to myofbroblasts due to chronic infammation [30]. Tis fact indicates that the decrease of vitamin A-rich and vitamin A-poor stellate cells correlates with the severity and progression of chronic hepatitis C is in line with the chronic hepatitis-liver cirrhosis-hepatocellular carcinoma (HCC) sequence proposed epidemiologically and clinically [31–33].

 Furthermore, chronic hepatitis C patients who are habitual smokers show decreased numbers of vitamin A-rich stellate cells or vitamin A-rich and vitamin A-poor stellate cells combined, compared with those who are non-smokers [29] (**Figure 5C**). Te smoking prevalence in the CAH2B group was 54.1%, which was

#### **Figure 5.**

*Relationship between the number of periportal vitamin A-rich stellate cells (SCs) and chronic hepatitis C. (A) Chronic hepatitis C monitored by serum ALT level. Both vitamin A-rich (*≥*10 lipid droplets in a cytoplasm) and vitamin A-poor (<10 lipid droplets) or vitamin A-rich stellate cells in the periportal area are significantly decreased in Group D (ALT >80 IU/L), compared with the groups with lower ALT level [28]. (B) Chronic hepatitis C. Both vitamin A-rich and vitamin A-poor stellate cells or vitamin A-rich stellate cells in the periportal area are significantly decreased in the CAH2B group compared with the CPH and CAH2A groups [29]. (C) Habitual smoking and the number of periportal vitamin A-rich stellate cells in patients with chronic hepatitis C. Smokers with chronic hepatitis C show low numbers of both vitamin A-rich and vitamin A-poor cells or vitamin A-rich stellate cells in the periportal area compared with non-smoking patients with chronic hepatitis C [29].* 

 approximately 1.8 times that of the CPH and CAH2A groups in this study. Habitual smoking is encountered in 59.4% of patients with HCC, according to a report by the Liver Cancer Study Group of Japan [34]. Tis fact suggests that habitual smoking in CPH and CAH2A may cause the clinicopathological progression of chronic hepatitis C, in line with the results of other studies reporting that smoking is a risk factor for HCC development [35, 36]. It is possible that the decrease in the number of periportal vitamin A-rich stellate cells causes a decrease in local vitamin A content and a reduction in the anti-infammatory efect of vitamin A. It has not yet been established whether the decrease of vitamin A-rich stellate cells results from harmful chemicals such as specifc nitrosamines or benzopyrenes associated with smoking [37, 38]. Te efects of the chemicals remain to be examined in stellate cell cultures to determine whether or not they result in hypoplasia of vitamin A-rich stellate cells.

In summary, habitual smoking can be a risk factor for acceleration of chronic hepatitis C, possibly due to a decrease or hypoplasia of vitamin A-rich stellate cells, resulting in the development of HCC.

## **3.2 Inhibition of dextran sulfate sodium (DSS) colitis by vitamin A supplementation**

 As a model of ulcerative colitis, DSS colitis was induced in mice fed a vitamin A defcient-diet or a vitamin A-supplemented diet [39, 40]. Subepithelial myofbroblasts in the colonic mucosa showed signifcant presence of cytoplasmic vitamin A lipid in the vitamin A-supplemented mice, in addition to the presence of vitamin A-rich hepatic stellate cells (**Figure 6**). Further, α smooth muscle (SM)-actinpositive subepithelial myofbroblasts increased in vitamin A-supplemented mice compared with vitamin A-defcient mice (**Figures 7**, **8A**). In addition, CD11cpositive macrophages in the colonic mucosa decreased in vitamin A-supplemented mice compared with vitamin A-defcient mice (**Figure 8B**). IgA-positive cells and the ratio of IgA-positive/IgG-positive cells increased in vitamin A-supplemented mice compared with vitamin A-defcient mice (**Figure 8C**). Experimental DSS colitis, as a murine model of ulcerative colitis, showed signifcantly higher severity of colitis and colonic ulcer, and shorter colon length in vitamin A-defcient mice compared with vitamin A-supplemented mice (**Figure 9**). In addition, recovery afer DSS colitis was delayed in vitamin A-defcient mice compared with vitamin A-supplemented mice. Te severity was greater in vitamin A-defcient mice than in vitamin A-supplemented mice with repeated bouts of DSS colitis.

Dietary vitamin A is required as a precursor of retinol in tissues. Tissue retinol plays an important role in immunity and cell diferentiation. In immunity, excess T1 and insufcient T2 function occur in vitamin A defciency, resulting in helper T cell imbalance. Further, α4β7-positive memory/activated T cell generation is reduced in vitamin A-defciency [41]. Supported by retinoic acid, a vitamin A metabolite, γδ T cells produce IL-22, leading to improvement of DSS-induced colitis [42]. CD11c-positive dendritic cells in the colonic mucosa of vitamin A-defcient mice are increased, in line with results shown in a study of vitamin A-defcient rats [9]. Te increase of CD11c-positive dendritic cells may represent a compensatory response to vitamin A defciency, which induces maturation of dendritic cells [43, 44], since vitamin A defciency causes dendritic cell dysfunction in the activation of T lymphocytes. Gut-homing IgA-secreting B cells are generated by intestinal dendritic cells in the sufcient vitamin A state [41]. Accordingly, a decrease in IgA+ cells or the ratio of IgA<sup>+</sup> cells/IgG+ in the colonic mucosa is thought to be indicative of disorganized mucosal immunity in vitamin A defciency [41, 45, 46]. Additionally,

*The Role of Vitamin A-Storing Cells (Stellate Cells) in Inflammation and Tumorigenesis DOI: http://dx.doi.org/10.5772/intechopen.83523* 

#### **Figure 6.**

*Subepithelial myofibroblasts of colonic mucosa in mice fed a vitamin A-deficient or vitamin A-supplemented diet. (A) A subepithelial myofibroblast from a vitamin A-supplemented mouse contains a few lipid droplets (arrow, upper panel). Conversely, a fibroblast-like subepithelial myofibroblast from a vitamin A-deficient mouse has no lipid droplets (lower panel). (B) Lipid droplets at the crypt base of vitamin A-supplemented mice were significantly more than in vitamin A-deficient mice [40].* 

#### **Figure 7.**

*Localization and distribution of CD11c-positive dendritic cells (green) and αSM-actin (red) in the colonic mucosa of vitamin A-deficient (B, vitamin A (−)) and vitamin A-supplemented mice (A, vitamin A (+)) [40].* 

intestinal epithelial expression of retinaldehyde dehydrogenase 1 (RLDH1) difers among mouse strains. BALB/c mice, which have high RLDH1, show an increased activity for induction of IgA class switching from B cells [42]. Te severity of DSS colitis might depend on RLDH1 expression, suggesting the possibility of diferences in susceptibility to ulcerative colitis in humans. Further studies should be conducted to clarify this possibility.

 Tus, possible dysfunction of mucosal immunity and poor epithelial cell diferentiation by malfunction of colonic subepithelial myofbroblasts in vitamin A-defcient mice are presumed to accelerate DSS colitis.

#### **Figure 8.**

*(A, B) Decreased αSM-actin-positive subepithelial myofibroblasts (a) and increased CD11c-positive dendritic cells (B) are shown in vitamin A-deficient mice (vitamin A (−)) compared with vitamin A-supplemented mice (vitamin A (+)), both in the non-treated and DSS colitis-induced groups [40]. (C) Comparison of IgA/ IgG-positive cells in the right side colonic mucosa between vitamin A-deficient and vitamin A-supplemented mice. IgA/IgG-positive cells increased in vitamin A-supplemented mice (vitamin A (+)), compared with vitamin A-deficient mice (vitamin A (−)) [40].* 

#### **3.3 Inhibition of development of colonic tumors by vitamin A supplementation in a DSS colitis model of the ulcerative colitis-carcinoma sequence**

 A combination of azoxymethane (AZM) preinjection followed by induction of DSS colitis is a well-known experimental murine model of the ulcerative colitisdysplasia-adenocarcinoma sequence [47]. Vitamin A-defcient mice developed more dysplasia and adenocarcinoma than vitamin A-supplemented mice, as well as more severe colitis (**Figures 10**, **11**) [40]. Tese results demonstrate that a vitamin A-supplemented diet inhibited DSS colitis and the subsequent development of dysplasia-carcinoma seen with a vitamin A-defcient diet.

 Cytoplasmic vitamin A lipids decreased in subepithelial myofbroblasts at the colonic crypt base of vitamin A-defcient mice compared with vitamin A-supplemented mice. Furthermore, a decrease in αSM-actin-positive subepithelial myofbroblasts was also found, suggesting dysfunction of niche regulation for the protection and diferentiation of mucosal stem cells or progenitor cells [3, 23, 25].

*The Role of Vitamin A-Storing Cells (Stellate Cells) in Inflammation and Tumorigenesis DOI: http://dx.doi.org/10.5772/intechopen.83523* 

#### **Figure 9.**

*Comparison of DSS colitis between vitamin A-deficient and vitamin A-supplemented mice. Vitamin A-supplemented mice showed improvement of colon length (A, B) and colitis score (C) assessed by erosion, loss of crypts, and inflammatory cell infiltration [40].* 

#### **Figure 10.**

*Colon cancer in vitamin A-deficient mouse induced by a combination of azoxymethane (AZM) injection and DSS colitis [40].* 

 Tese fndings might indicate that dysfunction of stem cell niche regulation in subepithelial myofbroblasts causes accelerated DSS colitis, resulting in the development of colorectal neoplasia.

 Vitamin A and its metabolites, retinoids, play an important role in cell diferentiation [25, 48]. It is well known and clinically accepted that retinoids have chemopreventive efects against cancers, particularly with diferentiation therapy for acute promyelocytic leukemia [49]. In addition, there are many clinical and experimental reports that vitamin A defciency promotes cancer development and progression [50–55]. Te CYP26A1 gene, which encodes for the cytochrome P450 enzyme involved in metabolic inactivation of retinoic acid, was highly expressed in cancers of various organs and is related to cancer progression. Tis may suggest a link between intracellular retinoic acid status and tumorigenesis [56–58]. Furthermore, prolonged recovery from severe DSS colitis and the subsequent development of

#### **Figure 11.**

*Comparison of induced colon neoplasia and DSS colitis between vitamin A-deficient and vitamin A-supplemented mice. Vitamin A-supplemented mice showed significant inhibition of neoplasia development (A) and reduction of colon shortness (B) and colitis (C) compared with vitamin A-deficient mice [40].* 

 colonic tumors in vitamin A-defcient mice were signifcantly improved by vitamin A supplementation, suggesting a cause-efect relationship between local vitamin A status and the development and progression of cancer.

 It has been shown that gut microbiota have a possible infuence on colitis and the development of colorectal neoplasia. Particularly, correction of microbiota-induced retinoic acid defciency stimulates protective CD8+ T cell-mediated immunity, resulting in inhibition of colitis and its associated colorectal tumorigenesis in mice [59]. Since malnutrition including vitamin A insufciency accelerates infammatory bowel disease in children [60, 61], it is thought that the diference in microbiota in response to a vitamin A-defcient versus a vitamin A-supplemented diet may have a substantial efect on colitis and the development of colonic neoplasia [62–64]. Further study is needed to address this possibility.

Tere are no defnite clinical indications for vitamin A administration to protect against infammation and tumor development, although it has been proposed that dietary vitamin A is closely related to exacerbation and continuity of infammation, particularly in chronic hepatitis C [65, 66] and infammatory bowel disease [67, 68]. Te results described herein raise the possibility that vitamin A administration inhibits chronic hepatitis and colitis, and the subsequent development of cancer. Further studies are needed to identify the possible mechanisms for inhibition of chronic infammation and subsequent neoplasia induced by vitamin A supplementation.

### **4. Conclusions**

 Vitamin A is stored in stellate cells, mainly in the liver and to a lesser extent in the lung and intestine, and plays important roles in immunity, cell diferentiation, and the stem cell niche. In the liver, decreased vitamin A-rich stellate cells, or decreased vitamin A-rich and vitamin A-poor stellate cells combined, relates to the severity of chronic hepatitis C and habitual smoking. In the colon, a vitamin A-supplemented diet inhibits DSS colitis and subsequent colonic tumor development in vitamin A-defcient diet mice, an experimental mouse model of ulcerative colitis. Vitamin A administration could be efective to treat and/or prevent liver

*The Role of Vitamin A-Storing Cells (Stellate Cells) in Inflammation and Tumorigenesis DOI: http://dx.doi.org/10.5772/intechopen.83523* 

disease and ulcerative colitis, although the clinical efects of vitamin A administration in this context have not been thoroughly characterized to date. Further study is needed to identify the efect of vitamin A administration on chronic infammation and tumorigenesis.
