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Inflammation rapidly modulates the expression of ALDH1A1 (RALDH1) and vimentin in the liver and hepatic macrophages of rats in vivo.

Ito K, Zolfaghari R, Hao L, Ross AC - Nutr Metab (Lond) (2014)

Bottom Line: ALDH1A1 protein exhibited diffuse staining in hepatocytes, with greater intensity in the periportal region including surrounding bile ducts.Alpha-smooth muscle actin staining was intense around blood vessels, but did not change after LPS or RA, nor overlap with staining for vimentin.In addition, the rapid strong response of vimentin expression after treatment with LPS suggests that increased vimentin may be a useful marker of early hepatic inflammation.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA 16802 USA.

ABSTRACT

Background: Members of the ALDH1 protein family, known as retinal dehydrogenases (RALDH), produce retinoic acid (RA), a metabolite of vitamin A, and may also oxidize other lipid aldehydes. Of three related ALDH1 genes, ALDH1A1 is most highly expressed in liver. ALDH1A1 is also rapidly gaining importance as a stem cell marker. We hypothesized that ALDH1A1 may have a broad cellular distribution in the liver, and that its expression may be regulated by RA and perturbed by inflammation.

Methods: Studies were conducted in vitamin A-deficient and -adequate rats that were further treated with all-trans-RA or lipopolysaccharide (LPS) to induce a state of moderate inflammation. RALDH1A1 expression was determined by quantitative PCR and RALDH1, as well as marker gene expression, was determined by immunocytochemical methods.

Results: Inflammation reduced ALDH1A1 mRNA in whole liver regardless of the level of vitamin A in the diet (P < 0.05), while treatment with RA reduced ALDH1A1 expression only in chow-fed rats. ALDH1A1 protein exhibited diffuse staining in hepatocytes, with greater intensity in the periportal region including surrounding bile ducts. Six h after administration of LPS, portal region macrophages were more numerous and some of these cells contained ALDH1A1. Vimentin, which was used as a marker for stellate cells and fibroblasts, was increased by LPS, P = 0.011 vs. without LPS, in both ED1 (CD68)-positive macrophages and fibroblastic stellate-like cells in the parenchyma as well as portal regions. Alpha-smooth muscle actin staining was intense around blood vessels, but did not change after LPS or RA, nor overlap with staining for vimentin.

Conclusions: Acute inflammation rapidly downregulates ALDH1A1 expression in whole liver while increasing its expression in periportal macrophages. Changes in ALDH1A1 expression appear to be part of the early acute-phase inflammatory response, which has been shown to alter the expression of other retinoid homeostatic genes. In addition, the rapid strong response of vimentin expression after treatment with LPS suggests that increased vimentin may be a useful marker of early hepatic inflammation.

No MeSH data available.


Related in: MedlinePlus

ALDH1A1 mRNA relative expression levels in 8-wk old rats fed chow diet (A and B) and in VAA and VAD rats (C). Total RNA was extracted from the liver samples of individual rats and quantified by real time PCR with SYBR Green for ALDH1A1 and 18S ribosomal RNA (rRNA) (A and C). Upon completion, the PCR products from individual samples in Figure 1A were pooled in each group and subjected to ethidium bromide agarose gel electrophoresis, with DNA molecular weight markers (MWM) (B). Values in A and C were individually normalized to 18S RNA and are expressed as the mean ± SEM of n = 4-6/group. Groups not sharing a common letter were significantly different, P <0.05 (a > b > c).
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Fig1: ALDH1A1 mRNA relative expression levels in 8-wk old rats fed chow diet (A and B) and in VAA and VAD rats (C). Total RNA was extracted from the liver samples of individual rats and quantified by real time PCR with SYBR Green for ALDH1A1 and 18S ribosomal RNA (rRNA) (A and C). Upon completion, the PCR products from individual samples in Figure 1A were pooled in each group and subjected to ethidium bromide agarose gel electrophoresis, with DNA molecular weight markers (MWM) (B). Values in A and C were individually normalized to 18S RNA and are expressed as the mean ± SEM of n = 4-6/group. Groups not sharing a common letter were significantly different, P <0.05 (a > b > c).

Mentions: In rats fed a normal chow diet, ALDH1A1 mRNA levels were reduced moderately after treatment with RA (P < 0.05), while treatment with low-dose LPS [24, 27, 29] for 6 h, as a model for the early stages of mild acute inflammation, resulted in a greater reduction of expression (P < 0.05 versus control and RA groups) (Figure 1A), and shown by gel electrophoresis of PCR products in Figure 1B. In rats fed VAA or VAD purified diets, vitamin A status at the end of the study differed significantly as shown by plasma retinol concentration (1.0 μM in VAA vs. 0.2 μM in VAD rats, respectively, P < 0.0001). However, there were no differences in body weight, indicating that the vitamin A deficiency was moderate. There were no differences in plasma retinol due to RA or LPS treatment, which may have been due to the short treatment. The relative abundance of ALDH1A1 mRNA did not differ after RA alone. It was reduced marginally but not statistically by LPS treatment in VAA rats (P < 0.05), and differed significantly in VAA rats treated with LPS + RA, P < 0.05 (Figure 1B). Therefore, both in rats fed chow diet (Figure 1A) and those fed purified diet (Figure 1C), ALDH1A1 mRNA was rapidly and significantly reduced after treatment either with LPS alone (Figure 1A) or with LPS in the presence of RA (Figure 1C).Figure 1


Inflammation rapidly modulates the expression of ALDH1A1 (RALDH1) and vimentin in the liver and hepatic macrophages of rats in vivo.

Ito K, Zolfaghari R, Hao L, Ross AC - Nutr Metab (Lond) (2014)

ALDH1A1 mRNA relative expression levels in 8-wk old rats fed chow diet (A and B) and in VAA and VAD rats (C). Total RNA was extracted from the liver samples of individual rats and quantified by real time PCR with SYBR Green for ALDH1A1 and 18S ribosomal RNA (rRNA) (A and C). Upon completion, the PCR products from individual samples in Figure 1A were pooled in each group and subjected to ethidium bromide agarose gel electrophoresis, with DNA molecular weight markers (MWM) (B). Values in A and C were individually normalized to 18S RNA and are expressed as the mean ± SEM of n = 4-6/group. Groups not sharing a common letter were significantly different, P <0.05 (a > b > c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4414379&req=5

Fig1: ALDH1A1 mRNA relative expression levels in 8-wk old rats fed chow diet (A and B) and in VAA and VAD rats (C). Total RNA was extracted from the liver samples of individual rats and quantified by real time PCR with SYBR Green for ALDH1A1 and 18S ribosomal RNA (rRNA) (A and C). Upon completion, the PCR products from individual samples in Figure 1A were pooled in each group and subjected to ethidium bromide agarose gel electrophoresis, with DNA molecular weight markers (MWM) (B). Values in A and C were individually normalized to 18S RNA and are expressed as the mean ± SEM of n = 4-6/group. Groups not sharing a common letter were significantly different, P <0.05 (a > b > c).
Mentions: In rats fed a normal chow diet, ALDH1A1 mRNA levels were reduced moderately after treatment with RA (P < 0.05), while treatment with low-dose LPS [24, 27, 29] for 6 h, as a model for the early stages of mild acute inflammation, resulted in a greater reduction of expression (P < 0.05 versus control and RA groups) (Figure 1A), and shown by gel electrophoresis of PCR products in Figure 1B. In rats fed VAA or VAD purified diets, vitamin A status at the end of the study differed significantly as shown by plasma retinol concentration (1.0 μM in VAA vs. 0.2 μM in VAD rats, respectively, P < 0.0001). However, there were no differences in body weight, indicating that the vitamin A deficiency was moderate. There were no differences in plasma retinol due to RA or LPS treatment, which may have been due to the short treatment. The relative abundance of ALDH1A1 mRNA did not differ after RA alone. It was reduced marginally but not statistically by LPS treatment in VAA rats (P < 0.05), and differed significantly in VAA rats treated with LPS + RA, P < 0.05 (Figure 1B). Therefore, both in rats fed chow diet (Figure 1A) and those fed purified diet (Figure 1C), ALDH1A1 mRNA was rapidly and significantly reduced after treatment either with LPS alone (Figure 1A) or with LPS in the presence of RA (Figure 1C).Figure 1

Bottom Line: ALDH1A1 protein exhibited diffuse staining in hepatocytes, with greater intensity in the periportal region including surrounding bile ducts.Alpha-smooth muscle actin staining was intense around blood vessels, but did not change after LPS or RA, nor overlap with staining for vimentin.In addition, the rapid strong response of vimentin expression after treatment with LPS suggests that increased vimentin may be a useful marker of early hepatic inflammation.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA 16802 USA.

ABSTRACT

Background: Members of the ALDH1 protein family, known as retinal dehydrogenases (RALDH), produce retinoic acid (RA), a metabolite of vitamin A, and may also oxidize other lipid aldehydes. Of three related ALDH1 genes, ALDH1A1 is most highly expressed in liver. ALDH1A1 is also rapidly gaining importance as a stem cell marker. We hypothesized that ALDH1A1 may have a broad cellular distribution in the liver, and that its expression may be regulated by RA and perturbed by inflammation.

Methods: Studies were conducted in vitamin A-deficient and -adequate rats that were further treated with all-trans-RA or lipopolysaccharide (LPS) to induce a state of moderate inflammation. RALDH1A1 expression was determined by quantitative PCR and RALDH1, as well as marker gene expression, was determined by immunocytochemical methods.

Results: Inflammation reduced ALDH1A1 mRNA in whole liver regardless of the level of vitamin A in the diet (P < 0.05), while treatment with RA reduced ALDH1A1 expression only in chow-fed rats. ALDH1A1 protein exhibited diffuse staining in hepatocytes, with greater intensity in the periportal region including surrounding bile ducts. Six h after administration of LPS, portal region macrophages were more numerous and some of these cells contained ALDH1A1. Vimentin, which was used as a marker for stellate cells and fibroblasts, was increased by LPS, P = 0.011 vs. without LPS, in both ED1 (CD68)-positive macrophages and fibroblastic stellate-like cells in the parenchyma as well as portal regions. Alpha-smooth muscle actin staining was intense around blood vessels, but did not change after LPS or RA, nor overlap with staining for vimentin.

Conclusions: Acute inflammation rapidly downregulates ALDH1A1 expression in whole liver while increasing its expression in periportal macrophages. Changes in ALDH1A1 expression appear to be part of the early acute-phase inflammatory response, which has been shown to alter the expression of other retinoid homeostatic genes. In addition, the rapid strong response of vimentin expression after treatment with LPS suggests that increased vimentin may be a useful marker of early hepatic inflammation.

No MeSH data available.


Related in: MedlinePlus