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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

Co-localization of ALDH1A1 protein expression and stellate cell/fibroblast marker, vimentin in liver from VAA rats. Results for VAD rats were similar and therefore are not shown. Dual IHC with anti-ALDH1A1 antibody and anti-vimentin antibody was performed followed by methyl green counterstaining for detection of nuclei. Staining controls for vimentin were similar to those shown for ED1 in Figure 4i. Panels c and d show false-color images after ilastik® processing (see Methods) so that only pink (vimentin) signals are visible as black. Arrows illustrate some of the cells that co-stained with purple (ALDH1A1) and vimentin signals (Figure 5a-f). Figure 5e illustrates the intense ALDH1A1 staining around bile duct structures (black arrow) and its absence around the arterial smooth muscle region (white arrow), which is also apparent in other sections. Magnification x 400. Figure 5g shows the tissue area occupied by vimentin staining, analyzed by ilastik®, which was significantly higher in the liver of rats treated with LPS (n = 8 animals) compared to those not treated with LPS (n = 9 animals, P = 0.011).
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Fig5: Co-localization of ALDH1A1 protein expression and stellate cell/fibroblast marker, vimentin in liver from VAA rats. Results for VAD rats were similar and therefore are not shown. Dual IHC with anti-ALDH1A1 antibody and anti-vimentin antibody was performed followed by methyl green counterstaining for detection of nuclei. Staining controls for vimentin were similar to those shown for ED1 in Figure 4i. Panels c and d show false-color images after ilastik® processing (see Methods) so that only pink (vimentin) signals are visible as black. Arrows illustrate some of the cells that co-stained with purple (ALDH1A1) and vimentin signals (Figure 5a-f). Figure 5e illustrates the intense ALDH1A1 staining around bile duct structures (black arrow) and its absence around the arterial smooth muscle region (white arrow), which is also apparent in other sections. Magnification x 400. Figure 5g shows the tissue area occupied by vimentin staining, analyzed by ilastik®, which was significantly higher in the liver of rats treated with LPS (n = 8 animals) compared to those not treated with LPS (n = 9 animals, P = 0.011).

Mentions: Additional localization studies with dual IHC using anti-ALDH1A1 and anti-ED1 (Figure 4), or anti-ALDH1A1 and anti-vimentin (Figure 5) were performed on the sections of liver from VAA and VAD rats. We did not observe a noticeable overall decrease in ALDH1A1 protein staining, which may have been due to the short time, just 6 h after the induction of inflammation. Similar to the distribution of ALDH1A1 mRNA, ALDH1A1 protein was present in the parenchyma and in the portal areas, especially surrounding bile ducts where intense staining was observed. ED1 staining (pink signals, Figure 4) was scattered throughout the liver, with more ED1 positive cells both within the portal areas, consistent with Figure 3, and in the nearby parenchyma of LPS-treated VAA and VAD rats. Again, the cells lining bile ducts, but not blood vessels, were stained for ALDH1A1 (seen in several images and marked with black and white arrows, respectively, in Figure 4 panel d). The negative staining control (panel i) was completely clean.Figure 4


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)

Co-localization of ALDH1A1 protein expression and stellate cell/fibroblast marker, vimentin in liver from VAA rats. Results for VAD rats were similar and therefore are not shown. Dual IHC with anti-ALDH1A1 antibody and anti-vimentin antibody was performed followed by methyl green counterstaining for detection of nuclei. Staining controls for vimentin were similar to those shown for ED1 in Figure 4i. Panels c and d show false-color images after ilastik® processing (see Methods) so that only pink (vimentin) signals are visible as black. Arrows illustrate some of the cells that co-stained with purple (ALDH1A1) and vimentin signals (Figure 5a-f). Figure 5e illustrates the intense ALDH1A1 staining around bile duct structures (black arrow) and its absence around the arterial smooth muscle region (white arrow), which is also apparent in other sections. Magnification x 400. Figure 5g shows the tissue area occupied by vimentin staining, analyzed by ilastik®, which was significantly higher in the liver of rats treated with LPS (n = 8 animals) compared to those not treated with LPS (n = 9 animals, P = 0.011).
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4414379&req=5

Fig5: Co-localization of ALDH1A1 protein expression and stellate cell/fibroblast marker, vimentin in liver from VAA rats. Results for VAD rats were similar and therefore are not shown. Dual IHC with anti-ALDH1A1 antibody and anti-vimentin antibody was performed followed by methyl green counterstaining for detection of nuclei. Staining controls for vimentin were similar to those shown for ED1 in Figure 4i. Panels c and d show false-color images after ilastik® processing (see Methods) so that only pink (vimentin) signals are visible as black. Arrows illustrate some of the cells that co-stained with purple (ALDH1A1) and vimentin signals (Figure 5a-f). Figure 5e illustrates the intense ALDH1A1 staining around bile duct structures (black arrow) and its absence around the arterial smooth muscle region (white arrow), which is also apparent in other sections. Magnification x 400. Figure 5g shows the tissue area occupied by vimentin staining, analyzed by ilastik®, which was significantly higher in the liver of rats treated with LPS (n = 8 animals) compared to those not treated with LPS (n = 9 animals, P = 0.011).
Mentions: Additional localization studies with dual IHC using anti-ALDH1A1 and anti-ED1 (Figure 4), or anti-ALDH1A1 and anti-vimentin (Figure 5) were performed on the sections of liver from VAA and VAD rats. We did not observe a noticeable overall decrease in ALDH1A1 protein staining, which may have been due to the short time, just 6 h after the induction of inflammation. Similar to the distribution of ALDH1A1 mRNA, ALDH1A1 protein was present in the parenchyma and in the portal areas, especially surrounding bile ducts where intense staining was observed. ED1 staining (pink signals, Figure 4) was scattered throughout the liver, with more ED1 positive cells both within the portal areas, consistent with Figure 3, and in the nearby parenchyma of LPS-treated VAA and VAD rats. Again, the cells lining bile ducts, but not blood vessels, were stained for ALDH1A1 (seen in several images and marked with black and white arrows, respectively, in Figure 4 panel d). The negative staining control (panel i) was completely clean.Figure 4

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