Effects of osmotic shrinkage on voltage-gated Ca2+ channel currents in rat anterior pituitary cells

Cherry juice alleviates high-fat diet-induced obesity in C57BL/6J mice by resolving gut microbiota dysbiosis and regulating microRNA

Cherry is a nutrient-rich food that is good for health. This study demonstrated the inhibitory action of dietary cherry juice on high-fat diet (HFD)-induced obesity in mice. Cherry juice intervention significantly decreased body weight, fat contents, and blood lipid levels in obese mice. The overproduction of proinflammatory cytokines was suppressed by dietary cherry juice, which was accompanied by the elevation of tight junction proteins to maintain intestinal barrier. Moreover, dietary cherry juice restored the decreased production of short-chain fatty acids (SCFAs) by regulating the composition and abundance of gut microbiota. In addition, dietary cherry juice also suppressed the expression of some microRNAs associated with obesity such as miR-200c-3p, miR-125a-5p, miR-132-3p, and miR-223-3p and target proteins related with microRNAs in the inguinal or epididymal white tissue in the obese mice. These results offer a fresh perspective on cherry juice's role in the prevention of obesity caused by the HFD.

Protective effect of sialyllactose on the intestinal epithelium in weaned pigs upon enterotoxigenic Escherichia coli challenge

Sialyllactose (SL), one of the most abundant oligosaccharides present in porcine breast milk, has been implicated in many biological functions, including the prebiotic and immune-modulating effects. This study was conducted to investigate the influences of dietary SL supplementation on intestinal barrier functions exposure to enterotoxigenic Escherichia coli (ETEC) in a porcine model. Thirty-two pigs were assigned to four treatments, fed with basal or SL-containing (5.0 g kg-1) diet, and orally infused with ETEC or culture medium. SL supplementation significantly reduced the diarrhea incidence and the abundance of E. coli in feces (P < 0.05). Interestingly, SL attenuated ETEC-induced intestinal epithelium injury as indicated by the decreased serum concentrations of diamine oxidase (DAO) and D-lactate and reduced the number of apoptotic cells in the jejunal epithelium (P < 0.05). Moreover, SL not only elevated the abundance of the tight-junction protein ZO-1 in the duodenal and ileal epithelium but also elevated the antioxidant capacity and the number of SIgA positive cells in the jejunal epithelium upon the ETEC challenge (P < 0.05). Importantly, SL decreased the expression levels of inflammation-related genes such as the tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), myeloid differentiation factor 88 (MyD88) in the duodenum, and ileum upon ETEC challenge (P < 0.05). SL also significantly elevated the expression levels of two critical antioxidant genes such as the nuclear factor erythroid-2 related factor 2 (Nrf-2) and kelch-like ECH-associated protein 1 (KEAP-1) in the jejunum (P < 0.05). These results suggested that SL can alleviate ETEC-induced intestinal epithelium injury, which is associated with suppressed inflammation, improved intestinal immunity, antioxidant capacity, and improved intestinal epithelial functions.

Voltage vs. Ligand I: Structural basis of the intrinsic flexibility of S3 segment and its significance in ion channel activation

We systematically predict the internal flexibility of the S3 segment, one of the most mobile elements in the voltage-sensor domain. By analyzing the primary amino acid sequences of V-sensor containing proteins, including Hv1, TPC channels and the voltage-sensing phosphatases, we established correlations between the local flexibility and modes of activation for different members of the VGIC superfamily. Taking advantage of the structural information available, we also assessed structural aspects to understand the role played by the flexibility of S3 during the gating of the pore. We found that S3 flexibility is mainly determined by two specific regions: (1) a short NxxD motif in the N-half portion of the helix (S3a), and (2) a short sequence at the beginning of the so-called paddle motif where the segment has a kink that, in some cases, divide S3 into two distinct helices (S3a and S3b). A good correlation between the flexibility of S3 and the reported sensitivity to temperature and mechanical stretch was found. Thus, if the channel exhibits high sensitivity to heat or membrane stretch, local S3 flexibility is low. On the other hand, high flexibility of S3 is preferentially associated to channels showing poor heat and mechanical sensitivities. In contrast, we did not find any apparent correlation between S3 flexibility and voltage or ligand dependence. Overall, our results provide valuable insights into the dynamics of channel-gating and its modulation.

Nomilin protects against cerebral ischemia–reperfusion induced neurological deficits and blood–brain barrier disruption via the Nrf2 pathway

Oxidative stress is considered to play an important role in the cerebral ischemia–reperfusion injury.

Ca2+ Channels in Anterior Pituitary Somatotrophs: A Therapeutic Perspective

Ca2+ influx through voltage-gated Ca2+ channels (VGCCs) plays a key role in GH secretion. In this review, we summarize the current state of knowledge regarding the physiology and molecular machinery of VGCCs in pituitary somatotrophs. We next discuss the possible involvement of Ca2+ channelopathies in pituitary disease and the potential use of Ca2+ channel blockers to treat pituitary disease. Various types of VGCCs exist in pituitary cells. However, because L-type Ca2+ channels (LTCCs) contribute the major component to Ca2+ influx in somatotrophs, lactotrophs, and corticotrophs, we focused on these channels. An increasing number of studies in recent years have linked genetic missense mutations in LTCCs to diseases of the human cardiovascular, nervous, and endocrine systems. These disease-associated genetic mutations occur at homologous functional positions (activation gates) in LTCCs. Thus, it is plausible that similar homologous missense mutations in pituitary LTCCs can cause abnormal hormone secretion and underlying pituitary disorders. The existence of LTCCs in pituitary cells opens questions about their sensitivity to dihydropyridines, a group of selective LTCC blockers. The dihydropyridine sensitivity of pituitary cells, as with any other excitable cell, depends primarily on two parameters: the pattern of their electrical activity and the dihydropyridine sensitivity of their LTCC isoforms. These two parameters are discussed in detail in relation to somatotrophs. These discussions are also relevant to lactotrophs and corticotrophs. High dihydropyridine sensitivity may facilitate their use as drugs to treat pituitary oversecretion disorders such as acromegaly, hyperprolactinemia, and Cushing disease.

Strain-specific properties of Lactobacillus plantarum for prevention of Salmonella infection

Salmonella is a common food-borne pathogen; since lactobacilli show great potential for protecting against Salmonella infections, they are used as dietary supplements in functional foods. The aim of this study is to investigate the strain-specific properties and the involved mechanisms of action of Lactobacillus plantarum towards prevention of Salmonella infection. Mice were pretreated with mixed strains or single strain of Lactobacillus plantarum for 10 d prior to infection with Salmonella typhimurium SL1344, and the survival rates showed that lactobacilli exhibited strain-specific properties for preventing Salmonella infection. Then, in vitro and in vivo studies were carried out to investigate the involved mechanism of the strain-specific properties. The results showed that different Lactobacillus plantarum strains had different effects on inhibiting Salmonella growth, thus preventing adhesion to and invasion of epithelial cells by pathogens and enhancing immune responses. The present study demonstrated strain-specific properties of probiotics to prevent Salmonella infection and elucidated their underlying mechanisms.

Multiple Ca2+ channel-dependent components in growth hormone secretion from rat anterior pituitary somatotrophs

The involvement of L-type Ca(2+) channels in both 'basal' and 'stimulated' growth hormone (GH) secretion is well established; however, knowledge regarding the involvement of non-L-type Ca(2+) channels is lacking. We investigated whether non-L-type Ca(2+) channels regulate GH secretion from anterior pituitary (AP) cells. To this end, GH secretion was monitored from dissociated AP cells, which were incubated for 15 min with 2 mm K(+) ('basal' secretion) or 60 mm K(+) ('stimulated' secretion). The role of non-L-type Ca(2+) influx was investigated using specific channel blockers, including ω-agatoxin-IVA, ω-conotoxin GVIA or SNX-482, to block P/Q-, N- or R-type Ca(2+) channels, respectively. Our results demonstrate that P/Q-, N- and R-type Ca(2+) channels contributed 21.2 ± 1.9%, 20.2 ± 7.6% and 11.4 ± 1.8%, respectively, to 'basal' GH secretion and 18.3 ± 1.0%, 24.4 ± 5.4% and 14.2 ± 4.8%, respectively, to 'stimulated' GH secretion. After treatment with a 'cocktail' that comprised the previously described non-L-type blockers, non-L-type Ca(2+) channels contributed 50.9 ± 0.4% and 45.5 ± 2.0% to 'basal' and 'stimulated' GH secretion, respectively. Similarly, based on the effects of nifedipine (10 μM), L-type Ca(2+) channels contributed 34.2 ± 3.7% and 54.7 ± 4.1% to 'basal' and 'stimulated' GH secretion, respectively. Interestingly, the relative contributions of L-type/non-L-type Ca(2+) channels to 'stimulated' GH secretion were well correlated with the relative contributions of L-type/non-L-type Ca(2+) channels to voltage-gated Ca(2+) influx in AP cells. Finally, we demonstrated that compartmentalisation of Ca(2+) channels is important for GH secretion. Lipid raft disruption (methyl-β-cyclodextrin, 10 mm) abrogated the compartmentalisation of Ca(2+) channels and substantially reduced 'basal' and 'stimulated' GH secretion by 43.2 ± 3.4% and 58.4 ± 4.0%, respectively. In summary, we have demonstrated that multiple Ca(2+) channel-dependent pathways regulate GH secretion. The proper function of these pathways depends on their compartmentalisation within AP cell membranes.

The impact of heat stress on intestinal function and productivity in grow-finish pigs

Heat stress is a physiological condition when animals can no longer regulate their internal euthermic temperature. When livestock such as pigs are subjected to this environmental stress, it can be detrimental to performance, health and well-being, and if severe enough even death. Growing pigs are particularly susceptible to heat stress and one of the major organs first affected by heat stress is the gastrointestinal tract. As a result, reductions in appetite, intestinal function and integrity and increased risk of endotoxemia can modify post-absorptive metabolism and tissue accretion. These changes in intestinal integrity may be a result of altered expression of tight junction proteins, increased circulating endotoxin concentrations and markers of cellular stress (heat shock and hypoxia response), which is evident as early on as 2 h after heat-stress onset. Due to restricted blood flow, the ileum is more severely affected compared with the colon. Interestingly, many of the negative effects of heat stress on intestinal integrity appear to be similar to those observed with pigs reared under reduced nutrient and caloric intakes. Altogether, these depress pig performance and health, and extend days to market. Despite this impact on the gastrointestinal tract, under heat-stress conditions, intestinal glucose transport pathways are upregulated. This review discussed how heat stress (directly and indirectly via reduced feed intake) affects intestinal integrity and how heat stress contributes to decreased growth performance in growing pigs.

Multiple pathways for high voltage-activated ca(2+) influx in anterior pituitary lactotrophs and somatotrophs

The present study demonstrates that a significant proportion of high voltage-activated (HVA) Ca(2+) influx in native rat anterior pituitary cells is carried through non-L-type Ca(2+) channels. Using whole-cell patch-clamp recordings and specific Ca(2+) channel toxin blockers, we show that approximately 35% of the HVA Ca(2+) influx in somatotrophs and lactotrophs is carried through Ca(v) 2.1, Ca(v) 2.2 and Ca(v) 2.3 channels, and that somatotrophs and lactotrophs share similar proportions of these non-L-type Ca(2+) channels. Furthermore, experiments on mixed populations of native anterior pituitary cells revealed that the fraction of HVA Ca(2+) influx carried through these non-L-type Ca(2+) channels might even be higher (approximately 46%), suggesting that non-L-type channels exist in the majority of native anterior pituitary cells. Using western blotting, immunoblots for α(1C) , α(1D) , α(1A) , α(1B) and α(1E) Ca(2+) channel subunits were identified in native rat anterior pituitary cells. Additionally, using reverse transcriptase-polymerase chain reaction, cDNA transcripts for α(1C) , α(1D) , α(1A) and α(1B) Ca(2+) channel subunits were identified. Transcripts for α(1E) were nonspecific and transcripts for α(1S) were not detected at all (control). Taken together, these results clearly demonstrate the existence of multiple HVA Ca(2+) channels in the membrane of rat native anterior pituitary cells. Whether these channels are segregated among different membrane compartments was investigated further in flotation assays, demonstrating that Ca(v) 2.1, Ca(v) 1.2 and caveolin-1 were mostly localised in light fractions of Nycodenz gradients (i.e. in lipid raft domains). Ca(v) 1.3 channels were distributed among both light and heavy fractions of the gradients (i.e. among raft and nonraft domains), whereas Ca(v) 2.2 and Ca(v) 2.3 channels were distributed mostly among nonraft domains. In summary, in the present study, we demonstrate multiple pathways for HVA Ca(2+) influx through L-type and non-L-type Ca(2+) channels in the membrane of native anterior pituitary cells. The compartmentalisation of these channels among raft and nonraft membrane domains might be essential for their proper regulation by separate receptors and signalling pathways.

Dynamic migration of γδ intraepithelial lymphocytes requires occludin

γδ intraepithelial lymphocytes (IELs) are located beneath or between adjacent intestinal epithelial cells and are thought to contribute to homeostasis and disease pathogenesis. Using in vivo microscopy to image jejunal mucosa of GFP γδ T-cell transgenic mice, we discovered that γδ IELs migrate actively within the intraepithelial compartment and into the lamina propria. As a result, each γδ IEL contacts multiple epithelial cells. Occludin is concentrated at sites of γδ IEL/epithelial interaction, where it forms a ring surrounding the γδ IEL. In vitro analyses showed that occludin is expressed by epithelial and γδ T cells and that occludin derived from both cell types contributes to these rings and to γδ IEL migration within epithelial monolayers. In vivo TNF administration, which results in epithelial occludin endocytosis, reduces γδ IEL migration. Further in vivo analyses demonstrated that occludin KO γδ T cells are defective in both initial accumulation and migration within the intraepithelial compartment. These data challenge the paradigm that γδ IELs are stationary in the intestinal epithelium and demonstrate that γδ IELs migrate dynamically to make extensive contacts with epithelial cells. The identification of occludin as an essential factor in γδ IEL migration provides insight into the molecular regulation of γδ IEL/epithelial interactions.

Effect of manganese chloride on the neurochemical profile of the rat hypothalamus

Manganese (Mn(2+))-enhanced magnetic resonance imaging studies of the neuronal pathways of the hypothalamus showed that information about the regulation of food intake and energy balance circulate through specific hypothalamic nuclei. The dehydration-induced anorexia (DIA) model demonstrated to be appropriate for studying the hypothalamus with Mn(2+)-enhanced magnetic resonance imaging. Manganese is involved in the normal functioning of a variety of physiological processes and is associated with enzymes contributing to neurotransmitter synthesis and metabolism. It also induces psychiatric and motor disturbances. The molecular mechanisms by which Mn(2+) produces alterations of the hypothalamic physiological processes are not well understood. (1)H-magnetic resonance spectroscopy measurements of the rodent hypothalamus are challenging due to the distant location of the hypothalamus resulting in limited measurement sensitivity. The present study proposed to investigate the effects of Mn(2+) on the neurochemical profile of the hypothalamus in normal, DIA, and overnight fasted female rats at 14.1 T. Results provide evidence that γ-aminobutyric acid has an essential role in the maintenance of energy homeostasis in the hypothalamus but is not condition specific. On the contrary, glutamine, glutamate, and taurine appear to respond more accurately to Mn(2+) exposure. An increase in glutamine levels could also be a characteristic response of the hypothalamus to DIA.

Lysophospholipids modulate voltage-gated calcium channel currents in pituitary cells; effects of lipid stress

Voltage-gated calcium channels (VGCCs) are osmosensitive. The hypothesis that this property of VGCCs stems from their susceptibility to alterations in the mechanical properties of the bilayer was tested on VGCCs in pituitary cells using cone-shaped lysophospholipids (LPLs) to perturb bilayer lipid stress. LPLs of different head group size and charge were used: lysophosphatidylcholine (LPC), lysophosphatidylinositol (LPI), lysophosphatidylserine (LPS) and lysophosphatidylethanolamine (LPE). Phosphatidylcholine (PC) and LPC (C6:0) were used as controls. We show that partition of both LPC and LPI into the membrane of pituitary cells suppressed L-type calcium channel currents (I(L)). This suppression of I(L) was slow in onset, reversible upon washout with BSA and associated with a depolarizing shift in activation ( approximately 8mV). In contrast to these effects of LPC and LPI on I(L), LPS, LPE, PC and LPC (C6:0) exerted minimal or insignificant effects. This difference may be attributed to the prominent conical shape of LPC and LPI compared to the shapes of LPS and LPE (which have smaller headgroups), and to PC (which is cylindrical). The similar effects of LPC and LPI on I(L), despite differences in the structure and charge of their headgroups suggest a common lipid stress dependent mechanism in their action on VGCCs.

Cannabinoids inhibit HIV-1 Gp120-mediated insults in brain microvascular endothelial cells

HIV-1 infection has significant effect on the immune system as well as on the nervous system. Breakdown of the blood-brain barrier (BBB) is frequently observed in patients with HIV-associated dementia (HAD) despite lack of productive infection of human brain microvascular endothelial cells (HBMEC). Cellular products and viral proteins secreted by HIV-1 infected cells, such as the HIV-1 Gp120 envelope glycoprotein, play important roles in BBB impairment and HIV-associated dementia development. HBMEC are a major component of the BBB. Using cocultures of HBMEC and human astrocytes as a model system for human BBB as well as in vivo model, we show for the first time that cannabinoid agonists inhibited HIV-1 Gp120-induced calcium influx mediated by substance P and significantly decreased the permeability of HBMEC as well as prevented tight junction protein down-regulation of ZO-1, claudin-5, and JAM-1 in HBMEC. Furthermore, cannabinoid agonists inhibited the transmigration of human monocytes across the BBB and blocked the BBB permeability in vivo. These results demonstrate that cannabinoid agonists are able to restore the integrity of HBMEC and the BBB following insults by HIV-1 Gp120. These studies may lead to better strategies for treatment modalities targeted to the BBB following HIV-1 infection of the brain based on cannabinoid pharmacotherapies.

Acrolein inhalation suppresses lipopolysaccharide-induced inflammatory cytokine production but does not affect acute airways neutrophilia

Acrolein is a reactive unsaturated aldehyde that is produced during endogenous oxidative processes and is a major bioactive component of environmental pollutants such as cigarette smoke. Because in vitro studies demonstrate that acrolein can inhibit neutrophil apoptosis, we evaluated the effects of in vivo acrolein exposure on acute lung inflammation induced by LPS. Male C57BL/6J mice received 300 microg/kg intratracheal LPS and were exposed to acrolein (5 parts per million, 6 h/day), either before or after LPS challenge. Exposure to acrolein either before or after LPS challenge did not significantly affect the overall extent of LPS-induced lung inflammation, or the duration of the inflammatory response, as observed from recovered lung lavage leukocytes and histology. However, exposure to acrolein after LPS instillation markedly diminished the LPS-induced production of several inflammatory cytokines, specifically TNF-alpha, IL-12, and the Th1 cytokine IFN-gamma, which was associated with reduction in NF-kappaB activation. Our data demonstrate that acrolein exposure suppresses LPS-induced Th1 cytokine responses without affecting acute neutrophilia. Disruption of cytokine signaling by acrolein may represent a mechanism by which smoking contributes to chronic disease in chronic obstructive pulmonary disease and asthma.

The tight junction protein, MUPP1, is up-regulated by hypertonicity and is important in the osmotic stress response in kidney cells

Antibody array proteomics was used to detect differentially expressed proteins in inner medullary collecting duct 3 (IMCD3) cells grown under isotonic and chronic hypertonic conditions. Of 512 potential proteins, >90% were unchanged in expression. Noteworthy was the up-regulation of several tight junction-related proteins, including MUPP1 (multi-PDZ protein-1), ZO1 (zonula occludens 1), and Af6. The most robustly up-regulated protein under hypertonic conditions was MUPP1 (7.2x, P < 0.001). Changes in expression for MUPP1 were verified by quantitative PCR for message and Western blot for protein. In mouse kidney tissues, MUPP1 expression was substantial in the papilla and was absent in the cortex. Furthermore, MUPP1 expression increased 253% (P < 0.01) in the papilla upon 36 h of thirsting. Localization of MUPP1 protein expression was confirmed by immunocytochemical analysis demonstrating only minor staining under isotonic conditions and the substantial presence in chronically adapted cells at the basolateral membrane. Message and protein half-life in IMCD3 cells were 26.2 and 17.8 h, respectively. Osmotic initiators of MUPP1 expression included NaCl, sucrose, mannitol, sodium acetate, and choline chloride but not urea. Stable IMCD3 clones silenced for MUPP1 expression used the pSM2-MUPP1 vector. In cell viability experiments, clones silenced for MUPP1 demonstrated only a minor loss in cell survival under acute sublethal osmotic stress compared with empty vector control cells. In contrast, a 24% loss (P < 0.02) in transepithelial resistance for monolayers of MUPP1-silenced cells was determined as compared with controls. These results suggest that MUPP1 specifically, and potentially tight junction complexes in general, are important in the renal osmoadaptive response.

Lipid stress at play: mechanosensitivity of voltage-gated channels

Membrane stretch modulates the activity of voltage-gated channels (VGCs). These channels are nearly ubiquitous among eukaryotes and they are present, too, in prokaryotes, so the potential ramifications of VGC mechanosensitivity are diverse. In situ traumatic stretch can irreversibly alter VGC activity with lethal results but that is pathology. This chapter discusses the reversible responses of VGCs to stretch, with the general relation of stretch stimuli to other forms of lipid stress, and briefly, with some irreversible stretch effects (=stretch trauma). A working assumption throughout is that mechanosensitive (MS) VGC motions-that is, motions that respond reversibly to bilayer stretch-are susceptible to other forms of lipid stress, such as the stresses produced when amphiphilic molecules (anesthetics, lipids, alcohols, and lipophilic drugs) are inserted into the bilayer. Insofar as these molecules change the bilayer's lateral pressure profile, they can be termed bilayer mechanical reagents (BMRs). The chapter also discusses the MS VGC behavior against the backdrop of eukaryotic channels more widely accepted as "MS channels"--namely, the transient receptor potential (TRP)-based MS cation channels.

Vesicular release of prolactin from preformed prolactin granules is stimulated by soluble factor(s) from the anterior pituitary of lactating rats

This study demonstrates that conditioned media (CM) from the anterior pituitary gland (AP) of lactating rats contains soluble factors that promote in vitro prolactin (PRL) release from the pituitary glands of male rats. CM-induced PRL release was confirmed by polyacrylamide gel electrophoresis, ELISA and bioassay. In cultured AP cells challenged with CM, increased intracellular staining with the dye FM1-43 was observed, suggesting vesicular PRL release and subsequent endocytosis. The percentage and hormone content of PRL-containing cells but not of growth hormone-containing cells increased in cultured male AP cells when exposed to CM. When the release of PRL, prelabeled with [3H] leucine for 30 min to 24 h was examined, no stimulatory effect of CM was observed, suggesting that released PRL originates from hormone synthesized more than 24 h earlier. Accordingly, the PRL content of mature granules from male pituitary tissues decreased after CM treatment. These findings were confirmed by electron microscopy immunogold PRL labeling. Treatment with inhibitors of protein synthesis or vesicle trafficking between the endoplasmic reticulum and the Golgi complex did not prevent the stimulatory effect of CM on PRL release. However, blockage of traffic to the plasma membrane completely abolished the effect of CM. These results suggest that CM from the AP of lactators contains soluble factor(s) capable of inducing rapid vesicular release of PRL in the male AP, which originates from preformed, mature granules by mechanisms independent of protein synthesis.