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. 2012;7(8):e43140.
doi: 10.1371/journal.pone.0043140. Epub 2012 Aug 14.

Expression and secretion of TNF-α in mouse taste buds: a novel function of a specific subset of type II taste cells

Pu Feng  1 , Hang Zhao, Jinghua Chai, Liquan Huang, Hong Wang
Affiliations

Expression and secretion of TNF-α in mouse taste buds: a novel function of a specific subset of type II taste cells

Pu Feng et al. PLoS One. 2012.

Abstract

Taste buds are chemosensory structures widely distributed on the surface of the oral cavity and larynx. Taste cells, exposed to the oral environment, face great challenges in defense against potential pathogens. While immune cells, such as T-cells and macrophages, are rarely found in taste buds, high levels of expression of some immune-response-associated molecules are observed in taste buds. Yet, the cellular origins of these immune molecules such as cytokines in taste buds remain to be determined. Here, we show that a specific subset of taste cells selectively expresses high levels of the inflammatory cytokine tumor necrosis factor-α (TNF-α). Based on immuno-colocalization experiments using taste-cell-type markers, the TNF-α-producing cells are predominantly type II taste cells expressing the taste receptor T1R3. These cells can rapidly increase TNF-α production and secretion upon inflammatory challenges, both in vivo and in vitro. The lipopolysaccharide (LPS)-induced TNF-α expression in taste cells was completely eliminated in TLR2(-/-)/TLR4(-/-) double-gene-knockout mice, which confirms that the induction of TNF-α in taste buds by LPS is mediated through TLR signaling pathways. The taste-cell-produced TNF-α may contribute to local immune surveillance, as well as regulate taste sensation under normal and pathological conditions.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Expression of TNF-α in the taste epithelium of control adult mice.
(A) qRT-PCR analysis of TNF-α expression in taste (TE) and nontaste (NT) epithelium: relative expression levels (fold) of the TNF-α gene. β-Actin served as the endogenous control gene for relative quantification. Epithelial tissues from 3 mice were pooled for each set of RNA sample preparation. Four independent sets of samples were established, and totally 12 mice were used in this study. Data are mean ±SD. **P<0.01 (t = 7.8, df = 6). (B–D) Confocal images of specific immunofluorescent staining of TNF-α in taste buds of fungiform papillae (FFP) (B), foliate papillae (FP) (C), and circumvallate papillae (CVP) (D). (E) No TNF-α expression was observed in nontaste epithelium (NT) adjacent to foliate papillae (FP). Arrows indicate TNF-α-positive cells in foliate taste buds. (F) Spleen (SP) was used as a positive-tissue control. (G) The specificity of the TNF-α antibody was determined by blocking the antibody with recombinant TNF-α protein before staining (Ag Blocking). (H) The specificity of the secondary antibody was tested by immunostaining with nonspecific goat IgG instead of the TNF-α antibody (Goat IgG). (I–L) Antibodies against CD11b (I, J) and CD3 (K, L) were used to identify macrophages and granulocytes (CD11b), as well as T lymphocytes (CD3), on circumvallate sections. Brown solid staining in connective tissues indicates specifically stained cells. Dotted lines indicate areas of taste epithelium in circumvallate papillae. Boxed regions in I and K are shown in J and L, respectively, as enlarged images. These images show that CD11b- and CD3-positive cells are in connective tissue layers but not in taste buds. Arrows indicate representative CD11b- and CD3-positive cells. Ten mice were used for panels B–F and I–L, and five were used for panels G–H. Scale bars: 10 µm (B), 25 µm (C, D, F), and 50 µm (E, G–L).
Figure 2
Figure 2. Identification of TNF-α-producing cells in taste buds.
Confocal images of double-immunofluorescent staining of TNF-α (green) and different taste cell type markers (red) on foliate papillae sections of control C57BL/6 mice, with high-magnification images shown in the far right panels. (A) Double immunostaining of TNF-α (green) and type I taste cell marker ectonucleotidase nucleoside triphosphate diphosphohydrolase (ENTPDase; red), showing no TNF-α expression in type I taste cells. (B) Double immunostaining of TNF-α (green) and type II taste cell marker phospholipase C-β2 (PLC-β2; red), showing TNF-α expression in a subset of type II taste cells. Note that all the TNF-α-producing cells express PLC-β2, and about half of PLC-β2-positive cells co-express TNF-α. (C) Double immunostaining of TNF-α (green) and type III taste cell marker neural cell adhesion molecule (NCAM; red), showing no TNF-α expression in type III taste cells. Five mice were included in each group of the experiment. Scale bars: 20 µm (A) and 30 µm (B and C).
Figure 3
Figure 3. Identification of specific type II taste cells that express TNF-α in mouse taste buds.
Confocal images of immunofluorescent staining of TNF-α and markers for different subtypes of type II taste cells on taste papillae sections of control C57BL/6 mice. (A) Top and middle panels: double immunostaining for TNF-α (green) and T1R3 (red), showing TNF-α expression in T1R3-positive taste cells in foliate (top) and circumvallate (CV; middle) papillae. Bottom panels: TNF-α immunostaining (red) in a fungiform (FF) papilla from a T1R3-GFP (green fluorescent protein) mouse. (B) Double immunostaining of TNF-α (green) and gustducin (red), showing the difference in TNF-α expression in gustducin-positive type II taste cells in foliate, circumvallate (CV), and fungiform (FF) papillae. Five mice were included in each group of the experiment. Scale bars: 35 µm.
Figure 4
Figure 4. Systemic administration of microbial LPS increases TNF-α expression in taste cells.
(A–D) Confocal images of double-immunofluorescent staining of TNF-α (green) and the type II taste cell marker PLC-β2 (red) on tissue sections of foliate (A, B) and circumvallate (C, D) papillae collected 3 h after PBS (vehicle control; A, C) or LPS (5 mg kg−1 body weight, i.p.; B, D) injection. Scale bars: 35 µm. (E) Numbers of TNF-α-positive cells and PLC-β2-positive cells from foliate (F) and circumvallate (CV) sections obtained from PBS- or LPS-treated mice. The percentage of TNF-α-positive cells in the population of PLC-β2-positive cells was calculated and plotted (TNF-α/PLC-β2 (%)). Data are mean ±SD (n = 5 mice). *P<0.05 (t = 3.2, df = 8), **P<0.01 (t = 5.3, df = 8), compared with PBS groups. (F) qRT-PCR analysis of TNF-α expression in taste epithelium (TE) containing circumvallate and foliate taste buds and in nontaste lingual epithelium (NT) of PBS- and LPS-treated mice. Relative expression levels (fold) of the TNF-α gene are shown. TNF-α expression level in nontaste epithelium of control mice (NT-PBS) was set to 1. β-Actin served as the endogenous control gene for relative quantification. For each mouse group, epithelial tissues from 2–3 mice were pooled for each set of RNA sample preparation. Four independent sets of samples were prepared, and totally 18 C57BL/6 mice were used in this study. Data are mean ±SD. **P<0.001 (t = 6.1, df = 6), compared with the PBS group.
Figure 5
Figure 5. Production and secretion of TNF-α by taste tissue upon LPS challenge in vitro.
Mouse taste epithelium (TE; circumvallate and foliate) and nontaste lingual epithelium (NT) were isolated and incubated in DMEM culture medium. The samples were treated with 5 µg ml−1 LPS for the time periods indicated. The cultures having no LPS in the medium served as controls. Concentrations of TNF-α in the supernatant of the cultured tissues were measured using ELISA. For each repeat of the experiment, tissues from three mice were used for medium control or LPS treatment. Each collected supernatant was assayed in duplicate for TNF-α concentration. The experiment was repeated three times, and the results were analyzed together. Data are mean ±SD. *P<0.01 (t = 4.3, df = 4), **P<0.001 (t = 9.8, df = 4), compared with medium control.
Figure 6
Figure 6. Absence of functional TLR2 and TLR4 genes attenuates LPS-induced TNF-α expression in taste buds.
LPS (5 mg kg−1 body weight) was given to TLR2−/−/TLR4−/− double-knockout mice and wild-type C57BL/6 mice via i.p. injection. The same volume of endotoxin-free PBS (vehicle) was administrated to control animals. At 3 h post-LPS challenge, TNF-α mRNA levels in circumvallate- and foliate-containing taste epithelium (TE) and nontaste lingual epithelium (NT) were determined using qRT-PCR. Relative levels (fold) of TNF-α mRNA expression are shown. The expression level of TNF-α mRNA in nontaste tissue of wild-type mice receiving PBS was arbitrarily defined as 1. β-Actin served as the endogenous control gene for relative quantification. The same sets of 18 C57BL/6 mice described in Figure 4F were used as wild-type control mice. Parallel samples from TLR2−/−/TLR4−/− mice were prepared. Totally 18 TLR2−/−/TLR4−/− mice were used in this study. Data are mean ±SD. **P<0.001 (ANOVA with post hoc Dunnett tests, Mean squared error  = 21.6, df = 16).
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References

    1. Mann NM (2002) Management of smell and taste problems. Cleve Clin J Med 69: 329–336. - PubMed
    1. Kim A, Feng P, Ohkuri T, Sauers D, Cohn ZJ, et al. (2012) Defects in the Peripheral Taste Structure and Function in the MRL/lpr Mouse Model of Autoimmune Disease. PLoS One 7: e35588. - PMC - PubMed
    1. Jones GJ, Itri LM (1986) Safety and tolerance of recombinant interferon alfa-2a (Roferon-A) in cancer patients. Cancer 57: 1709–1715. - PubMed
    1. Wang H, Zhou M, Brand J, Huang L (2007) Inflammation activates the interferon signaling pathways in taste bud cells. J Neurosci 27: 10703–10713. - PMC - PubMed
    1. Cohn ZJ, Kim A, Huang L, Brand J, Wang H (2010) Lipopolysaccharide-induced inflammation attenuates taste progenitor cell proliferation and shortens the life span of taste bud cells. BMC Neurosci 11: 72. - PMC - PubMed

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