The morphology of the vallate papillae from postmortem human samples was investigated with immuno... more The morphology of the vallate papillae from postmortem human samples was investigated with immunohistochemistry. Microscopically, taste buds were present along the inner wall of the papilla, and in some cases in the outer wall as well. The typical taste cell markers PLCβ2, GNAT3 (gustducin) and the T1R3 receptor stain elongated cells in human taste buds consistent with the Type II cells in rodents. In the human tissue, taste bud cells that stain with Type II cell markers, PLCβ2 and GNAT3, also stain with villin antibody. Two typical immunochemical markers for Type III taste cells in rodents, PGP9.5 and SNAP25, fail to stain any taste bud cells in the human postmortem tissue, although these antibodies do stain numerous nerve fibers throughout the specimen. Car4, another Type III cell marker, reacted with only a few taste cells in our samples. Finally, human vallate papillae have a general network of innervation similar to rodents and antibodies directed against SNAP25, PGP9.5, acetyl...
The expression of molecules involved in the transductory cascade of the sense of taste (TRs, alph... more The expression of molecules involved in the transductory cascade of the sense of taste (TRs, alpha-gustducin, PLCbeta2, IP3R3) has been described in lingual taste buds or in solitary chemoreceptor cells located in different organs. At the laryngeal inlet, immunocytochemical staining at the light and electron microscope levels revealed that alpha-gustducin and PLCbeta2 are mainly localized in chemosensory clusters (CCs), which are multicellular organizations differing from taste buds, being generally composed of two or three chemoreceptor cells. Compared with lingual taste buds, CCs are lower in height and smaller in diameter. In laryngeal CCs, immunocytochemistry using the two antibodies identified a similar cell type which appears rather unlike the alpha-gustducin-immunoreactive (IR) and PLCbeta2-IR cells visible in lingual taste buds. The laryngeal IR cells are shorter than the lingual ones, with poorly developed basal processes and their apical process is shorter and thicker. Some cells show a flask-like shape due to the presence of a large body and the absence of basal processes. CCs lack pores and their delimitation from the surrounding epithelium is poorly evident. The demonstration of the existence of CCs strengthens the hypothesis of a phylogenetic link between gustatory and solitary chemosensory cells.
The G-protein subunit α-gustducin is a marker of chemoreceptive cells. In the present study, we e... more The G-protein subunit α-gustducin is a marker of chemoreceptive cells. In the present study, we examined the immunohistochemical localization of α-gustducin in rat airway epithelium both by light and electron microscopy. α-Gustducin immunoreactivity was found in solitary cells that presented ultrastructural features of chemoreceptor cells, i.e. flask-shaped or pear-shaped, with an apical process with thin microvilli protruding into the lumen.
The G-protein subunit α-gustducin is a marker of chemoreceptive cells. In the present study, we e... more The G-protein subunit α-gustducin is a marker of chemoreceptive cells. In the present study, we examined the immunohistochemical localization of α-gustducin in rat airway epithelium both by light and electron microscopy. α-Gustducin immunoreactivity was found in solitary cells that presented ultrastructural features of chemoreceptor cells, i.e. flask-shaped or pear-shaped, with an apical process with thin microvilli protruding into the lumen.
Proceedings of the National Academy of Sciences of the United States of America, Jan 22, 2014
Solitary chemosensory cells (SCCs) of the nasal cavity are specialized epithelial chemosensors th... more Solitary chemosensory cells (SCCs) of the nasal cavity are specialized epithelial chemosensors that respond to irritants through the canonical taste transduction cascade involving Gα-gustducin and transient receptor potential melastatin 5. When stimulated, SCCs trigger peptidergic nociceptive (or pain) nerve fibers, causing an alteration of the respiratory rate indicative of trigeminal activation. Direct chemical excitation of trigeminal pain fibers by capsaicin evokes neurogenic inflammation in the surrounding epithelium. In the current study, we test whether activation of nasal SCCs can trigger similar local inflammatory responses, specifically mast cell degranulation and plasma leakage. The prototypical bitter compound, denatonium, a well-established activator of SCCs, caused significant inflammatory responses in WT mice but not mice with a genetic deletion of elements of the canonical taste transduction cascade, showing that activation of taste signaling components is sufficient...
The liver is one of the most complex organs in the body, which responds to hepatocellular damage ... more The liver is one of the most complex organs in the body, which responds to hepatocellular damage with inflammatory, regenerative and repair processes designed to restore functional liver tissue mass. Rat LRRP Ba1-651, a liver regeneration related protein induced during partial hepatectomy, is classified as a member of the aldehyde dehydrogenase (ALDh) 4A1 superfamily. During a BLAST protein search, this protein basically showed three structural and functional domains: an intermediate filament-like protein, a Delta-1-pyrroline-5-carboxylate dehydrogenase (P5CDh) and an atrial natriuretic factor (ANF) receptor. We suggest that all amniotic mammals possess a Ba1-651 ortholog to that of rats. The ANF receptor domain of rat LRRP Ba1-651, which domain is part of the receptor family ligand binding region, shows a very high sequence homology (almost identity) to the extracellular amino-terminal domains of the mammalian sweet taste receptor T1R2. This receptor belongs to the type C family of G protein coupled receptors (GPCRs) and is characterized by the presence of large extracellular amino-terminal domains, a nine cysteine domain of family 3 GPCR and a 7tm_3 transmembrane type domain. We suggest that rat LRRP Ba1-651 protein is a liver P5CDh-ANF that is activated by changes in the concentration of sweet molecules. If the sugar concentration in the organ increases due to liver damage or the intake of carbohydrate-rich or protein-rich foods, the P5CDh-ANF enzyme is activated to help in P5C catabolism. The hormone insulin probably plays a key role in the regulation of this enzyme. In the model that we propose, the P5CDh-ANF enzyme is activated by a conformational change in protein structure in the P5C docking site due to sugars binding in the AFN receptor region of the LRRP Ba1-651 protein. Our research could be a further understanding of the biological significance of this P5CDh-ANF enzyme, with important potential applications in the treatment of HPII and liver diseases and in liver transplantation. Further studies of our P5CDh-ANF enzyme are needed to clarify its features and functions, and which substances are involved in its induction. These might use liver cell lines or purified LRRP Ba1-651 protein with sweet molecules in vitro. Other experiments may help to localize LRRP Bal-651 in the organ and to link its abnormal presence or absence to certain tumors like hepatocellular carcinoma.
The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 2009
Acyl homoserine lactones (AHLs) are intercellular signaling molecules used in quorum sensing by G... more Acyl homoserine lactones (AHLs) are intercellular signaling molecules used in quorum sensing by Gram-negative bacteria. We studied the early effects on the rat airway of in vivo intratracheal administration of AHLs (i.e., P. aeruginosa and B. cepacia) to test the hypothesis that AHLs also act on the airway cells, modifying secretory mechanisms which are important in mucosal defense. One hour after treatment, N-butyryl-homoserine lactone (C4-HL) had caused dilated extracellular spaces, loss of cilia, reduction of secretory material, and the presence of pre-necrotic elements in the epithelium, while N-octanoyl-homoserine lactone (C8-HL) caused a mild lesion in the epithelium. After treatment with either C4- or C8-HL, reduced immunoreactivity was found using CC10 antibody. At ultrastructural examination, dilatation of the mitochondria was evident in ciliate and secretory cells, while solitary chemosensory cells appeared better preserved, showing aspects of nucleocytoplasmic activation. Using microarray analysis, we found down-regulation of early gene Fos and Egr1 in all AHL-treated specimens. In vivo pharmacological magnetic resonance imaging after C4- or C8-HL treatment showed a slight increase in tracheal secretion at a first evaluation 5 min after administration, with no increase in the following minutes. In conclusion, AHLs induce an early mucosal response, and the chondriomas of ciliate and secretory cells are the main cytological target of AHL action. Our results show that AHL action is not limited to activation of conspecific bacteria, but also modifies innate airway defense mechanisms.
The morphology of the vallate papillae from postmortem human samples was investigated with immuno... more The morphology of the vallate papillae from postmortem human samples was investigated with immunohistochemistry. Microscopically, taste buds were present along the inner wall of the papilla, and in some cases in the outer wall as well. The typical taste cell markers PLCβ2, GNAT3 (gustducin) and the T1R3 receptor stain elongated cells in human taste buds consistent with the Type II cells in rodents. In the human tissue, taste bud cells that stain with Type II cell markers, PLCβ2 and GNAT3, also stain with villin antibody. Two typical immunochemical markers for Type III taste cells in rodents, PGP9.5 and SNAP25, fail to stain any taste bud cells in the human postmortem tissue, although these antibodies do stain numerous nerve fibers throughout the specimen. Car4, another Type III cell marker, reacted with only a few taste cells in our samples. Finally, human vallate papillae have a general network of innervation similar to rodents and antibodies directed against SNAP25, PGP9.5, acetyl...
The expression of molecules involved in the transductory cascade of the sense of taste (TRs, alph... more The expression of molecules involved in the transductory cascade of the sense of taste (TRs, alpha-gustducin, PLCbeta2, IP3R3) has been described in lingual taste buds or in solitary chemoreceptor cells located in different organs. At the laryngeal inlet, immunocytochemical staining at the light and electron microscope levels revealed that alpha-gustducin and PLCbeta2 are mainly localized in chemosensory clusters (CCs), which are multicellular organizations differing from taste buds, being generally composed of two or three chemoreceptor cells. Compared with lingual taste buds, CCs are lower in height and smaller in diameter. In laryngeal CCs, immunocytochemistry using the two antibodies identified a similar cell type which appears rather unlike the alpha-gustducin-immunoreactive (IR) and PLCbeta2-IR cells visible in lingual taste buds. The laryngeal IR cells are shorter than the lingual ones, with poorly developed basal processes and their apical process is shorter and thicker. Some cells show a flask-like shape due to the presence of a large body and the absence of basal processes. CCs lack pores and their delimitation from the surrounding epithelium is poorly evident. The demonstration of the existence of CCs strengthens the hypothesis of a phylogenetic link between gustatory and solitary chemosensory cells.
The G-protein subunit α-gustducin is a marker of chemoreceptive cells. In the present study, we e... more The G-protein subunit α-gustducin is a marker of chemoreceptive cells. In the present study, we examined the immunohistochemical localization of α-gustducin in rat airway epithelium both by light and electron microscopy. α-Gustducin immunoreactivity was found in solitary cells that presented ultrastructural features of chemoreceptor cells, i.e. flask-shaped or pear-shaped, with an apical process with thin microvilli protruding into the lumen.
The G-protein subunit α-gustducin is a marker of chemoreceptive cells. In the present study, we e... more The G-protein subunit α-gustducin is a marker of chemoreceptive cells. In the present study, we examined the immunohistochemical localization of α-gustducin in rat airway epithelium both by light and electron microscopy. α-Gustducin immunoreactivity was found in solitary cells that presented ultrastructural features of chemoreceptor cells, i.e. flask-shaped or pear-shaped, with an apical process with thin microvilli protruding into the lumen.
Proceedings of the National Academy of Sciences of the United States of America, Jan 22, 2014
Solitary chemosensory cells (SCCs) of the nasal cavity are specialized epithelial chemosensors th... more Solitary chemosensory cells (SCCs) of the nasal cavity are specialized epithelial chemosensors that respond to irritants through the canonical taste transduction cascade involving Gα-gustducin and transient receptor potential melastatin 5. When stimulated, SCCs trigger peptidergic nociceptive (or pain) nerve fibers, causing an alteration of the respiratory rate indicative of trigeminal activation. Direct chemical excitation of trigeminal pain fibers by capsaicin evokes neurogenic inflammation in the surrounding epithelium. In the current study, we test whether activation of nasal SCCs can trigger similar local inflammatory responses, specifically mast cell degranulation and plasma leakage. The prototypical bitter compound, denatonium, a well-established activator of SCCs, caused significant inflammatory responses in WT mice but not mice with a genetic deletion of elements of the canonical taste transduction cascade, showing that activation of taste signaling components is sufficient...
The liver is one of the most complex organs in the body, which responds to hepatocellular damage ... more The liver is one of the most complex organs in the body, which responds to hepatocellular damage with inflammatory, regenerative and repair processes designed to restore functional liver tissue mass. Rat LRRP Ba1-651, a liver regeneration related protein induced during partial hepatectomy, is classified as a member of the aldehyde dehydrogenase (ALDh) 4A1 superfamily. During a BLAST protein search, this protein basically showed three structural and functional domains: an intermediate filament-like protein, a Delta-1-pyrroline-5-carboxylate dehydrogenase (P5CDh) and an atrial natriuretic factor (ANF) receptor. We suggest that all amniotic mammals possess a Ba1-651 ortholog to that of rats. The ANF receptor domain of rat LRRP Ba1-651, which domain is part of the receptor family ligand binding region, shows a very high sequence homology (almost identity) to the extracellular amino-terminal domains of the mammalian sweet taste receptor T1R2. This receptor belongs to the type C family of G protein coupled receptors (GPCRs) and is characterized by the presence of large extracellular amino-terminal domains, a nine cysteine domain of family 3 GPCR and a 7tm_3 transmembrane type domain. We suggest that rat LRRP Ba1-651 protein is a liver P5CDh-ANF that is activated by changes in the concentration of sweet molecules. If the sugar concentration in the organ increases due to liver damage or the intake of carbohydrate-rich or protein-rich foods, the P5CDh-ANF enzyme is activated to help in P5C catabolism. The hormone insulin probably plays a key role in the regulation of this enzyme. In the model that we propose, the P5CDh-ANF enzyme is activated by a conformational change in protein structure in the P5C docking site due to sugars binding in the AFN receptor region of the LRRP Ba1-651 protein. Our research could be a further understanding of the biological significance of this P5CDh-ANF enzyme, with important potential applications in the treatment of HPII and liver diseases and in liver transplantation. Further studies of our P5CDh-ANF enzyme are needed to clarify its features and functions, and which substances are involved in its induction. These might use liver cell lines or purified LRRP Ba1-651 protein with sweet molecules in vitro. Other experiments may help to localize LRRP Bal-651 in the organ and to link its abnormal presence or absence to certain tumors like hepatocellular carcinoma.
The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 2009
Acyl homoserine lactones (AHLs) are intercellular signaling molecules used in quorum sensing by G... more Acyl homoserine lactones (AHLs) are intercellular signaling molecules used in quorum sensing by Gram-negative bacteria. We studied the early effects on the rat airway of in vivo intratracheal administration of AHLs (i.e., P. aeruginosa and B. cepacia) to test the hypothesis that AHLs also act on the airway cells, modifying secretory mechanisms which are important in mucosal defense. One hour after treatment, N-butyryl-homoserine lactone (C4-HL) had caused dilated extracellular spaces, loss of cilia, reduction of secretory material, and the presence of pre-necrotic elements in the epithelium, while N-octanoyl-homoserine lactone (C8-HL) caused a mild lesion in the epithelium. After treatment with either C4- or C8-HL, reduced immunoreactivity was found using CC10 antibody. At ultrastructural examination, dilatation of the mitochondria was evident in ciliate and secretory cells, while solitary chemosensory cells appeared better preserved, showing aspects of nucleocytoplasmic activation. Using microarray analysis, we found down-regulation of early gene Fos and Egr1 in all AHL-treated specimens. In vivo pharmacological magnetic resonance imaging after C4- or C8-HL treatment showed a slight increase in tracheal secretion at a first evaluation 5 min after administration, with no increase in the following minutes. In conclusion, AHLs induce an early mucosal response, and the chondriomas of ciliate and secretory cells are the main cytological target of AHL action. Our results show that AHL action is not limited to activation of conspecific bacteria, but also modifies innate airway defense mechanisms.
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Papers by Marco Tizzano