The functions of dendritic cells (DCs) are tightly regulated such that protective immune responses are elicited and unwanted immune responses are prevented. 1α25-dihydroxyvitamin D3 (1α25(OH)2D3) has been identified as a major factor that inhibits the differentiation and maturation of DCs, an effect dependent upon its binding to the nuclear vitamin D receptor (VDR). Physiological control of 1α25(OH)2D3 levels is critically dependent upon 25-hydroxyvitamin D3-1α-hydroxylase (1αOHase), a mitochondrial cytochrome P450 enzyme that catalyzes the conversion of inactive precursor 25-hydroxyvitamin D3 (25(OH)D3) to the active metabolite 1α25(OH)2D3. Using a human monocyte-derived DC (moDC) model, we have examined the relationship between DC VDR expression and the impact of exposure to its ligand, 1α25(OH)2D3. We show for the first time that moDCs are able to synthesize 1α25(OH)2D3 in vitro as a consequence of increased 1αOHase expression. Following terminal differentiation induced by a diverse set of maturation stimuli, there is marked transcriptional up-regulation of 1αOHase leading to increased 1αOHase enzyme activity. Consistent with this finding is the observation that the development and function of moDCs is inhibited at physiological concentrations of the inactive metabolite 25(OH)D3. In contrast to 1αOHase, VDR expression is down-regulated as monocytes differentiate into immature DCs. Addition of 1α25(OH)2D3 to moDC cultures at different time points indicates that its inhibitory effects are greater in monocyte precursors than in immature DCs. In conclusion, differential regulation of endogenous 1α25(OH)2D3 ligand and its nuclear receptor appear to be important regulators of DC biology and represent potential targets for the manipulation of DC function.

In dogs and in humans, potassium channels formed by ether-a-go-go-related gene 1 protein ERG1 (KCNH2) and KCNQ1 alpha-subunits, in association with KCNE beta-subunits, play a role in normal repolarization and may contribute to abnormal repolarization associated with long QT syndrome (LQTS). The molecular basis of repolarization in horse heart is unknown, although horses exhibit common cardiac arrhythmias and may receive drugs that induce LQTS. In horse heart, we have used immunoblotting and immunostaining to demonstrate the expression of ERG1, KCNQ1, KCNE1, and KCNE3 proteins and RT-PCR to detect KCNE2 message. Peptide N-glycosidase F-sensitive forms of horse ERG1 (145 kDa) and KCNQ1 (75 kDa) were detected. Both ERG1 and KCNQ1 coimmunoprecipitated with KCNE1. Cardiac action potential duration was prolonged by antagonists of either ERG1 (MK-499, cisapride) or KCNQ1/KCNE1 (chromanol 293B). Patch-clamp analysis confirmed the presence of a slow delayed rectifier current. These data suggest that repolarizing currents in horses are similar to those of other species, and that horses are therefore at risk for acquired LQTS. The data also provide unique evidence for coassociation between ERG1 and KCNE1 in cardiac tissue.

Ceftiofur sodium may be an acceptable broad spectrum antimicrobial to administer IA in septic arthritic equine joints.

Glucocorticoids (GCs) exert powerful antiinflammatory effects that may relate in part to their ability to restrict the differentiation and function of dendritic cells (DCs). Although these inhibitory effects are dependent upon GCs binding to nuclear glucocorticoid receptors (GRs), fine-tuning of GR signaling is achieved by prereceptor interconversion of cortisol that binds GRs with high affinity and cortisone that does not. We show for the first time that human monocyte-derived DCs are able to generate cortisol as a consequence of up-regulated expression of the enzyme 11␤-hydroxysteroid dehydrogenase type 1 (11␤-HSD1). Immature DCs demonstrate selective enhancement of 11␤-HSD1 reductase activity, leading to increased conversion of inactive cortisone to active cortisol. Enhancement of GC bioavailability is maintained or increased upon terminal differentiation induced by signals associated with innate immune activation. In marked contrast, maturation induced by CD40 ligation leads to a sharp reduction in cortisol generation by DCs. The differentiation of DCs from monocyte precursors is inhibited at physiologic concentrations of inactive cortisone, an effect that requires activity of the 11␤-HSD1 enzyme. In conclusion, prereceptor regulation of endogenous GCs appears to be an important determinant of DC function and represents a potential target for therapeutic manipulation. ( IntroductionSynthetic derivatives of naturally occurring glucocorticoids (GCs) have major anti-inflammatory and immunosuppressive properties that make them suitable for the treatment of autoimmune disease or the prevention of allograft rejection. 1 Rational design of novel synthetic GC derivatives or of strategies that enable their optimal use requires an improved understanding of how exogenous and endogenous GCs exert their effects upon the immune system. Studies in vitro which use GCs at supraphysiologic concentrations suggest that major cellular targets are T cells 2,3 and dendritic cells (DCs). [4][5][6][7][8][9] In the latter case, GCs inhibit in vitro differentiation of DCs from their precursor cells [4][5][6]9 and impair their capacity to undergo terminal differentiation or generate proinflammatory cytokines. [5][6][7][8][9] The role of endogenous GCs in modulating DC development or function however is unknown.Crucial to any concept that seeks to explain how endogenous GCs influence DC development is an appreciation of how GC levels are regulated in vivo. Endogenous GCs exist either as active 11-hydroxy ligands (eg, cortisol) that bind glucocorticoid receptor ␣ (GR␣) or inactive 11-keto derivatives which do not (eg, cortisone). 10,11 Fine-tuning of active GC bioavailability in peripheral tissues is regulated by prereceptor interconversion of inactive and active ligands mediated by 2 isozymes of 11␤-hydroxysteroid dehydrogenase (11␤-HSD) that catalyze the so-called "cortisolcortisone" shuttle. 10,11 Inactivation of cortisol by dehydrogenation to cortisone is mediated by 11␤-HSD2. In the kidney, this activity prevents competition betwee...

The KvLQT1 and minK subunits that coassemble to form I(sK) channels, contain potential N-glycosylation sites. To examine the role of glycosylation in channel function, a Chinese hamster ovary cell line deficient in glycosylation (Lec-1) and its parental cell line (Pro-5) were transiently transfected with human KvLQT1 (hKvLQT1) cDNA, alone and in combination with the rat (rminK) or human minK (hminK) cDNA. Functional KvLQT1 and I(sK) currents were expressed in both cell lines, although amplitudes were larger in Pro-5 than Lec-1 cells transfected with hKvLQT1 and hKvLQT1/hminK. For I(sK), but not KvLQT1, the voltage-dependence of activation was shifted to more positive voltages and the activation kinetics were slower in the Lec-1 compared to the Pro-5 cells. The effect of extracellular acidification on recombinant KvLQT1 and I(sK) currents was investigated in Pro-5 and Lec-1 cells. Changing external pH (pH(o)) from 7.4 to 6.0 significantly decreased the amplitude and increased the half-activation voltage (V(1/2)) of KvLQT1 currents in Pro-5 and Lec-1 cells. In Pro-5 cells, decreasing pH(o) reduced I(sK) amplitude without increasing V(1/2), whether rminK or hminK was coexpressed with hKvLQT. In contrast, changing pH(o) from 7.4 to 6.0 did not significantly change I(sK) amplitude in Lec-1 cells. Thus, oligosaccharides attached to the minK subunit affect not only the gating properties, but also the pH sensitivity of I(sK).

Non-steroidal anti-inflammatory drugs (NSAIDs) contribute to gastrointestinal ulcer formation by inhibiting epithelial cell migration and mucosal restitution; however, the drug-affected signaling pathways are poorly defined. We investigated whether NSAID inhibition of intestinal epithelial migration is associated with depletion of intracellular polyamines, depolarization of membrane potential (E m ) and altered surface expression of K + channels. Epithelial cell migration in response to the wounding of confluent IEC-6 and IEC-Cdx2 monolayers was reduced by indomethacin (100 μM), phenylbutazone (100 μM) and NS-398 (100 μM) but not by SC-560 (1 μM). NSAIDinhibition of intestinal cell migration was not associated with depletion of intracellular polyamines. Treatment of IEC-6 and IEC-Cdx2 cells with indomethacin, phenylbutazone and NS-398 induced significant depolarization of E m , whereas treatment with SC-560 had no effect on E m . The E m of IEC-Cdx2 cells was: −38.5±1.8 mV under control conditions; −35.9±1.6 mV after treatment with SC-560; −18.8±1.2 mV after treatment with indomethacin; and −23.7±1.4 mV after treatment with NS-398. Whereas SC-560 had no significant effects on the total cellular expression of K v 1.4 channel protein, indomethacin and NS-398 decreased not only the total cellular expression of K v 1.4, but also the cell surface expression of both K v 1.4 and K v 1.6 channel subunits in IEC-Cdx2. Both K v 1.4 and K v 1.6 channel proteins were immunoprecipitated by K v 1.4 antibody from IEC-Cdx2 lysates, indicating that these subunits co-assemble to form heteromeric K v channels. These results suggest that NSAID inhibition of epithelial cell migration is independent of polyamine-depletion, and is associated with depolarization of E m and decreased surface expression of heteromeric K v 1 channels.

We have studied delayed rectifier K+ currents (IK) in cells isolated from the sinoatrial node (SAN) region of the guinea pig. Using whole cell patch-clamp procedures, we measured the voltage dependence of IK activation and IK kinetics and the IK equilibrium potential in 4.8 mM extracellular K concentration solutions. Experiments were designed to contrast properties of guinea pig SAN IK with those of IK recorded from SAN cells of the rabbit. We find that guinea pig SAN IK differs from IK recorded from single rabbit SAN cells in its activation threshold, and in the absence of inactivation of whole cell currents recorded over a wide voltage range. These results, along with the relative insensitivity of guinea pig SAN IK to E-4031 and lanthanum, suggest that under our experimental conditions, a strongly rectifying IK component (IK,r) is not the major component of delayed rectification in the guinea pig SAN, as it appears to be in SAN cells of the rabbit.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are used extensively as therapeutic agents, despite their well documented gastrointestinal (GI) toxicity. At this time, the mechanisms responsible for NSAID-associated GI damage are incompletely understood. In this study, we used microarray analysis to generate a novel hypothesis about cellular mechanisms that underlie the GI toxicity of Accordingly, quantitative real-time reverse transcription polymerase chain reaction and immunoblotting were performed to assess the effects of NSAIDs on the expression of mRNA and protein for calpain 8, calpain 2, calpain 1, and calpastatin. In treated IEC-6 monolayers, NS-398 decreased the expression of mRNA for calpain 2 and calpain 8. Both NS-398 and indomethacin decreased the protein expression of calpains 8, 2, and 1. None of the NSAIDs affected expression of calpastatin mRNA or protein. The calpain inhibitors, N-acetyl-Leu-Leu-methioninal and N-acetyl-Leu-LeuNle-CHO, retarded IEC-6 cell migration in a concentration-dependant fashion, and these inhibitory effects were additive with those of indomethacin and NS-398. Our experimental results suggest that the altered expression of calpain proteins may contribute to the adverse effects of NSAIDs on intestinal epithelial restitution.Nonsteroidal anti-inflammatory drugs (NSAIDs) are used extensively as therapeutic agents despite their well documented gastrointestinal (GI) toxicity. Adverse gastrointestinal effects of NSAIDs in humans and other species include oral, gastric, duodenal, and colonic ulceration (Lichtenberger, 2001;Tomisato et al., 2004). Despite exhaustive investigation, the mechanisms responsible for NSAID-associated GI damage are not completely understood. Evidence gathered to date suggests that NSAIDs may promote ulcer formation not only by inhibiting mucosal cyclooxygenase (COX) and decreasing cytoprotective prostaglandins (PGs) but also by adversely influencing intestinal microflora, neutrophil recruitment, surface hydrophobicity, and epithelial restitution (Lichtenberger, 2001;Little et al., 2007). Although the inhibition of COX isoforms has received much attention and investigation as the basis of GI