Optogenetic activation of mechanically insensitive afferents in mouse colorectum reveals chemosensitivity

The sensory innervation of the distal colorectum includes mechanically insensitive afferents (MIAs; ~25%), which acquire mechanosensitivity in persistent visceral hypersensitivity and thus generate de novo input to the central nervous system. We utilized an optogenetic approach to bypass the process of transduction (generator potential) and focus on transformation (spike initiation) at colorectal MIA sensory terminals, which is otherwise not possible in typical functional studies. From channelrhodopsin2-expressing mice (driven by Advillin-Cre), the distal colorectum with attached pelvic nerve was harvested for ex vivo single-fiber recordings. Afferent receptive fields (RFs) were identified by electrical stimulation and tested for response to mechanical stimuli (probing, stroking, and stretch), and afferents were classified as either MIAs or mechanosensitive afferents (MSAs). All MIA and MSA RFs were subsequently stimulated optically and MIAs were also tested for activation/sensitization with inflammatory soup (IS), acidic hypertonic solution (AHS), and/or bile salts (BS). Responses to pulsed optical stimuli (1–10 Hz) were comparable between MSAs and MIAs whereas 43% of MIAs compared with 86% of MSAs responded tonically to stepped optical stimuli. Tonic-spiking MIAs responded preferentially to AHS (an osmotic stimulus) whereas non-tonic-spiking MIAs responded to IS (an inflammatory stimulus). A significant proportion of MIAs were also sensitized by BS. These results reveal transformation as a critical factor underlying the differences between MIAs (osmosensors vs. inflammatory sensors), revealing a previously unappreciated heterogeneity of MIA endings. The current study draws attention to the sensory encoding of MIA nerve endings that likely contribute to afferent sensitization and thus have important roles in visceral pain.

From: Feng, B., Joyce, S. C., Gebhart, G. F. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG790%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Butyrate enhances antibacterial effects while suppressing other features of alternative activation in IL-4-induced macrophages

The short-chain fatty acid butyrate is produced by fermentation of dietary fiber by the intestinal microbiota; butyrate is the primary energy source of colonocytes and has immunomodulatory effects. Having shown that macrophages differentiated with IL-4 [M(IL-4)s] can suppress colitis, we hypothesized that butyrate would reinforce an M(IL-4) phenotype. Here, we show that in the presence of butyrate M(IL-4)s display reduced expression of their hallmark markers Arg1 and Ym1 and significantly suppressed LPS-induced nitric oxide, IL-12p40, and IL-10 production. Butyrate treatment likely altered the M(IL-4) phenotype via inhibition of histone deacetylation. Functionally, M(IL-4)s treated with butyrate showed increased phagocytosis and killing of bacteria, compared with M(IL-4) and this was not accompanied by enhanced proinflammatory cytokine production. Culture of regulatory T cells with M(IL-4)s and M(IL-4 + butyrate)s revealed that both macrophage subsets suppressed expression of the regulatory T-cell marker Foxp3. However, Tregs cocultured with M(IL-4 + butyrate) produced less IL-17A than Tregs cocultured with M(IL-4). These data illustrate the importance of butyrate, a microbial-derived metabolite, in the regulation of gut immunity: the demonstration that butyrate promotes phagocytosis in M(IL-4)s that can limit T-cell production of IL-17A reveals novel aspects of bacterial-host interaction in the regulation of intestinal homeostasis.

From: Fernando, M. R., Saxena, A., Reyes, J.-L., McKay, D. M. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG822%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Intestinal inflammation requires FOXO3 and prostaglandin E2-dependent lipogenesis and elevated lipid droplets

Intestinal inflammation has been recently characterized by the dysregulation of lipids as metabolic and energy sources, revealing a novel feature of its pathophysiology. Because intracellular lipids, stored in dynamic lipid droplets (LDs), provide energy for cellular needs, we investigated whether they play a role in intestinal inflammation. In the inflamed intestine of mice, elevated LDs were found in colonic and infiltrating immune cells as shown by staining for the LD coat protein PLIN2 and for lipids with BODIPY. In colonic cells, TNF stimulated LD increases by receptor signaling rely on phosphatidylinositol 3-kinase activation. Downstream, TNF triggered a negative regulatory loop between LDs and the transcription factor FOXO3. This was shown in the colon of Foxo3-deficient mice, where elevation in PLIN2 and lipids were further facilitated by inflammation and were more prominent relative to wild-type, whereas, in colonic cells, inhibition of lipogenesis blocked the TNF-mediated loss of FOXO3. Furthermore, blockade of PGE2 synthesis abrogated TNF-stimulated increases in LDs and FOXO3 inactivation. We found in colonic tissue of Foxo3-deficient mice higher levels of cyclooxygenase-2, a mediator of prostaglandin E2 (PGE2) synthesis, supporting involvement of PGE2 in the LD-FOXO3 regulatory loop. Ultimately, TNF-stimulated lipogenesis leading to elevated LDs facilitated NF-B-mediated increases in IL-8 protein, which is associated with the surface of LDs found in the lumina of the endoplasmic reticulum and Golgi apparatus. This novel immunometabolic mechanism of colonic inflammation involving elevated LDs could provide opportunities for new treatment options.

From: Heller, S., Cable, C., Penrose, H., Makboul, R., Biswas, D., Cabe, M., Crawford, S. E., Savkovic, S. D. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG844%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Enhanced ethanol catabolism in orphan nuclear receptor SHP-null mice

Deficiency of the orphan nuclear hormone receptor small heterodimer partner (SHP, NR0B2) protects mice from diet-induced hepatic steatosis, in part, via repression of peroxisome proliferator-activated receptor (PPAR)-₂ (Pparg2) gene expression. Alcoholic fatty liver diseases (AFLD) share many common pathophysiological features with non-AFLD. To study the role of SHP and PPAR₂ in AFLD, we used a strategy of chronic ethanol feeding plus a single binge ethanol feeding to challenge wild-type (WT) and SHP-null (SHP^–/–) mice with ethanol. The ethanol feeding induced liver fat accumulation and mRNA expression of hepatic Pparg2 in WT mice, which suggests that a high level of PPAR₂ is a common driving force for fat accumulation induced by ethanol or a high-fat diet. Interestingly, ethanol-fed SHP^–/– mice displayed hepatic fat accumulation similar to that of ethanol-fed WT mice, even though their Pparg2 expression level remained lower. Mortality of SHP^–/– mice after ethanol binge feeding was significantly reduced and their acetaldehyde dehydrogenase (Aldh2) mRNA level was higher than that of their WT counterparts. After an intoxicating dose of ethanol, SHP^–/– mice exhibited faster blood ethanol clearance and earlier wake-up time than WT mice. Higher blood acetate, the end product of ethanol metabolism, and lower acetaldehyde levels were evident in the ethanol-challenged SHP^–/– than WT mice. Ethanol-induced inflammatory responses and lipid peroxidation were also lower in SHP^–/– mice. The current data show faster ethanol catabolism and extra fat storage through conversion of acetate to acetyl-CoA before its release into the circulation in this ethanol-feeding model in SHP^–/– mice.

From: Park, J. E., Lee, M., Mifflin, R., Lee, Y. K. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG799%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Hydrophobic bile acid apoptosis is regulated by sphingosine-1-phosphate receptor 2 in rat hepatocytes and human hepatocellular carcinoma cells

The hepatotoxic bile acid glycochenodeoxycholate (GCDC) modulates hepatocyte cell death through activation of JNK, Akt, and Erk. The nonhepatotoxic bile acid taurocholate activates Akt and Erk through the sphingosine-1-phosphate receptor 2 (S1PR2). The role of the S1PR2 in GCDC-mediated apoptosis and kinase activation is unknown. Studies were done in rat hepatocytes, HUH7 cells, and HUH7 cells stably transfected with rat Ntcp (HUH7-Ntcp). Cells were treated with GCDC and apoptosis was monitored morphologically by Hoechst staining and biochemically by immunoblotting for the active cleaved fragment of caspase 3. Kinase activation was determined by immunoblotting with phospho-specific antibodies. JTE-013, an inhibitor of S1PR2, significantly attenuated morphological evidence of GCDC-induced apoptosis and prevented caspase 3 cleavage in rat hepatocytes and HUH7-Ntcp cells. In hepatocytes, JTE-013 mildly suppressed, augmented, and had no effect on GCDC-induced JNK, Akt, and Erk phosphorylation, respectively. Similar results were seen in HUH7-Ntcp cells except for mild suppression of JNK and Erk phosphorylation. Knockdown of S1PR2 in HUH7-Ntcp augmented Akt, inhibited JNK, and had no effect on Erk phosphorylation. GCDC failed to induce apoptosis or kinase activation in HUH7 cells. In conclusion, SIPR2 inhibition attenuates GCDC-induced apoptosis and inhibits and augments GCDC-induced JNK and Akt phosphorylation, respectively. In addition, GCDC must enter hepatocytes to mediate cell death or activate kinases. These results suggest that SIPR2 activation is proapoptotic in GCDC-induced cell death but that this effect is not due to direct ligation of the S1PR2 by the bile acid.

From: Webster, C. R. L., Anwer, M. S. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG865%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Postprandial lymphatic pump function after a high-fat meal: a characterization of contractility, flow, and viscosity

Dietary lipids are transported from the intestine through contractile lymphatics. Chronic lipid loads can adversely affect lymphatic function. However, the acute lymphatic pump response in the mesentery to a postprandial lipid meal has gone unexplored. In this study, we used the rat mesenteric collecting vessel as an in vivo model to quantify the effect of lipoproteins on vessel function. Lipid load was continuously monitored by using the intensity of a fluorescent fatty-acid analog, which we infused along with a fat emulsion through a duodenal cannula. The vessel contractility was simultaneously quantified. We demonstrated for the first time that collecting lymphatic vessels respond to an acute lipid load by reducing pump function. High lipid levels decreased contraction frequency and amplitude. We also showed a strong tonic response through a reduction in the end-diastolic and systolic diameters. We further characterized the changes in flow rate and viscosity and showed that both increase postprandially. In addition, shear-mediated Ca²⁺ signaling in lymphatic endothelial cells differed when cultured with lipoproteins. Together these results show that the in vivo response could be both shear and lipid mediated and provide the first evidence that high postprandial lipid has an immediate negative effect on lymphatic function even in the acute setting.

From: Kassis, T., Yarlagadda, S. C., Kohan, A. B., Tso, P., Breedveld, V., Dixon, J. B. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG776%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Lin28 and let-7: roles and regulation in liver diseases

The diagnosis and treatment of liver disease remain a major health concern worldwide because of the diverse etiologies of this disease. For this reason, new therapeutic targets are greatly needed to halt the progression of this damaging disease. Upon initiation of liver injury by viral infection, autoimmune disease or toxin, and/or hepatitis, chronic disease may develop, which can progress to cirrhosis, hepatocellular carcinoma (HCC), cholangiocarcinoma, liver failure, or death. The Lin28/lethal-7 (let-7) molecular switch has emerged as a central regulator of multiorgan injuries and cancer development. Lin28 is a stem cell marker vital to initiation or maintenance of a stem cell phenotype. Lin28 has not been extensively studied in the liver, despite its ability to induce tissue regeneration via reprogramming of oxidative enzymes in other tissues and its involvement with numerous upstream regulators and downstream targets in liver disease. Theoretically, overexpression of Lin28 in certain forms of liver disease could be a potential treatment that aids in liver regeneration. Alternatively, Lin28 has been implicated numerous times in the progression of diverse cancer types and is associated with increased severity of disease. In this case, Lin28 could be a potential inhibitory target to prevent malignant transformation in the liver. This review seeks to characterize the role of Lin28 in liver disease.

From: McDaniel, K., Hall, C., Sato, K., Lairmore, T., Marzioni, M., Glaser, S., Meng, F., Alpini, G. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG757%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

MAG-EPA reduces severity of DSS-induced colitis in rats

Ulcerative colitis (UC) is a chronic disease characterized by diffuse inflammation of the intestinal mucosa of the large bowel. Omega-3 (3) fatty acid supplementation has been associated with a decreased production of inflammatory cytokines involved in UC pathogenesis. The aim of this study was to determine the preventive and therapeutic potential of eicosapentaenoic acid monoglyceride (MAG-EPA) in an in vivo rats model of UC induced by dextran sulfate sodium (DSS). DSS rats were untreated or treated per os with MAG-EPA. Morphological, histological, and biochemical analyses were performed following MAG-EPA administrations. Morphological and histological analyses revealed that MAG-EPA pretreatment (12 days pre-DSS) and treatment (6 days post-DSS) exhibited strong activity in reducing severity of disease in DSS rats. Following MAG-EPA administrations, tissue levels of the proinflammatory cytokines TNF-α, IL-1β, and IL-6 were markedly lower compared with rats treated only with DSS. MAG-EPA per os administration decrease neutrophil infiltration in colon tissues, as depicted by myelohyperoxidase activity. Results also revealed a reduced activation of NF-B pathways correlated with a decreased expression of COX-2 in colon homogenates derived from MAG-EPA-pretreated and treated rats. Tension measurements performed on colon tissues revealed that contractile responses to methacholine and relaxing effect induced by sodium nitroprusside were largely increased following MAG-EPA treatment. The combined treatment of MAG-EPA and vitamin E displayed an antagonistic effect on anti-inflammatory properties of MAG-EPA in DSS rats.

From: Morin, C., Blier, P. U., Fortin, S. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG808%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Prevention of gallbladder hypomotility via FATP2 inhibition protects from lithogenic diet-induced cholelithiasis

Gallstone disease is a widespread disorder costing billions for annual treatment in the United States. The primary mechanisms underlying gallstone formation are biliary cholesterol supersaturation and gallbladder hypomotility. The relative contribution of these two processes has been difficult to dissect, as experimental lithogenic diets cause both bile supersaturation and alterations in gallbladder motility. Importantly, there is no mechanistic explanation for obesity as a major risk factor for cholelithiasis. We discovered that lithogenic diets induce ectopic triacylglycerol (TAG) accumulation, a major feature of obesity and a known muscle contraction impairing condition. We hypothesized that prevention of TAG accumulation in gallbladder walls may prevent gallbladder contractile dysfunction without impacting biliary cholesterol saturation. We utilized adeno-associated virus-mediated knock down of the long-chain fatty acid transporter 2 (FATP2; Slc27A2), which is highly expressed by gallbladder epithelial cells, to downregulate lithogenic diet-associated TAG accumulation. FATP2-knockdown significantly reduced gallbladder TAG, but did not affect key bile composition parameters. Importantly, measurements with force displacement transducers showed that contractile strength in FATP2-knockdown gallbladders was significantly greater than in control gallbladders following lithogenic diet administration, and the magnitude of this effect was sufficient to prevent the formation of gallstones. FATP2-driven fatty acid uptake and the subsequent TAG accumulation in gallbladder tissue plays a pivotal role in cholelithiasis, and prevention of this process can protect from gallstone formation, even in the context of supersaturated bile cholesterol levels, thus pointing to new treatment approaches and targets.

From: Tharp, K. M., Khalifeh-Soltani, A., Park, H. M., Yurek, D. A., Falcon, A., Wong, L., Feng, R., Atabai, K., Stahl, A. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG855%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

5-HT4-mediated neuroprotection: a new therapeutic modality on the way?

From: Gershon, M. D. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Ffull%2F310%2F10%2FG766%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Fibroblast growth factor 21 and exercise-induced hepatic mitochondrial adaptations

Exercise stimulates hepatic mitochondrial adaptations; however, the mechanisms remain largely unknown. Here we tested whether FGF21 plays an obligatory role in exercise induced hepatic mitochondrial adaptations by testing exercise responses in FGF21 knockout mice. FGF21 knockout (FGF21-KO) and wild-type (WT) mice (11–12 wk of age) had access to voluntary running wheels for exercise (EX) or remained sedentary for 8 wk. FGF21 deficiency resulted in greater body weight, adiposity, serum cholesterol, insulin, and glucose concentrations compared with WT mice (P < 0.05). In addition, hepatic mitochondrial complete palmitate oxidation, β-hydroxyacyl-CoA dehydrogenase (β-HAD) activity, and nuclear content of PGC-1α were 30–50% lower in FGF21-KO mice compared with WT mice (P < 0.01). EX effectively lowered body weight, adiposity, serum triglycerides, free fatty acids, and insulin and normalized mitochondrial complete palmitate oxidation in the FGF21-KO mice, whereas the reduced hepatic β-HAD activity and lowered nuclear content of PGC-1α in FGF21-KO mice were not restored by EX. In addition, EX increased hepatic CPT-1α mRNA expression and ACC phosphorylation (a marker of increased AMPK activity) and reduced hepatic triacylglycerol content in both genotypes. However, FGF21-KO mice displayed a lower EX-induced increase in the mRNA expression of the hepatic gluconeogenic gene, PEPCK, compared with WT. In conclusion, FGF21 does not appear necessary for exercise-induced systemic and hepatic mitochondrial adaptations, but the increased adiposity, hyperinsulinemia, and impairments in hepatic mitochondrial function induced by FGF21 deficiency can be partially rescued by daily wheel running exercise.

From: Fletcher, J. A., Linden, M. A., Sheldon, R. D., Meers, G. M., Morris, E. M., Butterfield, A., Perfield, J. W., Thyfault, J. P., Rector, R. S. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG832%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Inhibition of pancreatic acinar mitochondrial thiamin pyrophosphate uptake by the cigarette smoke component 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone

Thiamin is essential for normal metabolism in pancreatic acinar cells (PAC) and is obtained from their microenvironment through specific plasma-membrane transporters, converted to thiamin pyrophosphate (TPP) in the cytoplasm, followed by uptake of TPP by mitochondria through the mitochondrial TPP (MTPP) transporter (MTPPT; product of SLC25A19 gene). TPP is essential for normal mitochondrial function. We examined the effect of long-term/chronic exposure of PAC in vitro (pancreatic acinar 266-6 cells) and in vivo (wild-type or transgenic mice carrying the SLC25A19 promoter) of the cigarette smoke toxin, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), on the MTPP uptake process. Our in vitro and in vivo findings demonstrate that NNK negatively affects MTPP uptake and reduced expression of MTPPT protein, MTPPT mRNA, and heterogenous nuclear RNA, as well as SLC25A19 promoter activity. The effect of NNK on Slc25a19 transcription was neither mediated by changes in expression of transcriptional factor NFY-1 (known to drive SLC25A19 transcription), nor due to changes in methylation profile of the Slc25a19 promoter. Rather, it appears to be due to changes in histone modifications that involve significant decreases in histone H3K4-trimethylation and H3K9-acetylation (activation markers). The effect of NNK on MTPPT function is mediated through the nonneuronal α7-nicotinic acetylcholine receptor (α7-nAChR), as indicated by both in vitro (using the nAChR antagonist mecamylamine) and in vivo (using an α7-nAchR^–/– mouse model) studies. These findings demonstrate that chronic exposure of PAC to NNK negatively impacts PAC MTPP uptake. This effect appears to be exerted at the level of Slc25a19 transcription, involve epigenetic mechanism(s), and is mediated through the α7-nAchR.

From: Srinivasan, P., Thrower, E. C., Gorelick, F. S., Said, H. M. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG874%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Prucalopride exerts neuroprotection in human enteric neurons

Serotonin (5-hydroxytryptamine, 5-HT) and its transporters and receptors are involved in a wide array of digestive functions. In particular, 5-HT₄ receptors are known to mediate intestinal peristalsis and recent data in experimental animals have shown their role in neuronal maintenance and neurogenesis. This study has been designed to test whether prucalopride, a well-known full 5-HT₄ agonist, exerts protective effects on neurons, including enteric neurons, exposed to oxidative stress challenge. Sulforhodamine B assay was used to determine the survival of SH-SY5Y cells, human enteric neurospheres, and ex vivo submucosal neurons following H₂O₂ exposure in the presence or absence of prucalopride (1 nM). Specificity of 5-HT₄-mediated neuroprotection was established by experiments performed in the presence of GR113808, a 5-HT₄ antagonist. Prucalopride exhibited a significant neuroprotective effect. SH-SY5Y cells pretreated with prucalopride were protected from the injury elicited by H₂O₂ as shown by increased survival (73.5 ± 0.1% of neuronal survival vs. 33.3 ± 0.1%, respectively; P < 0.0001) and a significant reduction of proapoptotic caspase-3 and caspase-9 activation in all neurons tested. The protective effect of prucalopride was reversed by the specific 5-HT₄ antagonist GR113808. Prucalopride promotes a significant neuroprotection against oxidative-mediated proapoptotic mechanisms. Our data pave the way for novel therapeutic implications of full 5-HT₄ agonists in gut dysmotility characterized by neuronal degeneration, which go beyond the well-known enterokinetic effect.

From: Bianco, F., Bonora, E., Natarajan, D., Vargiolu, M., Thapar, N., Torresan, F., Giancola, F., Boschetti, E., Volta, U., Bazzoli, F., Mazzoni, M., Seri, M., Clavenzani, P., Stanghellini, V., Sternini, C., De Giorgio, R. http://redirect.viglink.com?u=http%3A%2F%2Fajpgi.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F310%2F10%2FG768%3Frss%3D1&key=ddaed8f51db7bb1330a6f6de768a69b8

Just keep going

After a terrifying car accident leaves him in a vegetative state, a young athlete confounds experts with his remarkable recovery

From: http://redirect.viglink.com?u=http%3A%2F%2Fwww.cbsnews.com%2Fnews%2Fjust-keep-going%2F&key=ddaed8f51db7bb1330a6f6de768a69b8

​Almanac: Listerine

On May 15, 1923, a trademark was awarded for the first over-the-counter mouthwash

From: http://redirect.viglink.com?u=http%3A%2F%2Fwww.cbsnews.com%2Fnews%2Falmanac-listerine%2F&key=ddaed8f51db7bb1330a6f6de768a69b8