scholarly journals Calcium-sensing receptor signaling pathways in medullary thick ascending limb cells mediate COX-2-derived PGE2 production: functional significance

2008 ◽  
Vol 295 (4) ◽  
pp. F1082-F1089 ◽  
Author(s):  
Huda Ismail Abdullah ◽  
Paulina L. Pedraza ◽  
John C. McGiff ◽  
Nicholas R. Ferreri
Keyword(s):  
Ion Transport ◽  
Dominant Negative ◽  
Prostaglandin E ◽  
Thick Ascending Limb ◽  
Calcium Sensing Receptor ◽  
Activated T Cells ◽  
Calcium Sensing ◽  
Medullary Thick Ascending Limb ◽  
Cox 2

We determined the functional implications of calcium-sensing receptor (CaR)-dependent, Gq- and Gi-coupled signaling cascades, which work in a coordinated manner to regulate activity of nuclear factor of activated T cells and tumor necrosis factor (TNF)-α gene transcription that cause expression of cyclooxygenase (COX)-2-derived prostaglandin E2 (PGE2) synthesis by rat medullary thick ascending limb cells (mTAL). Interruption of Gq, Gi, protein kinase C (PKC), or calcineurin (CaN) activities abolished CaR-mediated COX-2 expression and PGE2 synthesis. We tested the hypothesis that these pathways contribute to the effects of CaR activation on ion transport in mTAL cells. Ouabain-sensitive O2 consumption, an in vitro correlate of ion transport in the mTAL, was inhibited by ∼70% in cells treated for 6 h with extracellular Ca2+ (1.2 mM), an effect prevented in mTAL cells transiently transfected with a dominant negative CaR overexpression construct (R796W), indicating that the effect was initiated by stimulation of the CaR. Pretreatment with the COX-2-selective inhibitor, NS-398 (1 μM), reversed CaR-activated decreases in ouabain-sensitive O2 consumption by ∼60%, but did not alter basal levels of ouabain-sensitive O2 consumption. Similarly, inhibition of either Gq, Gi, PKC, or CaN, which are components of the mechanism associated with CaR-stimulated COX-2-derived PGE2 synthesis, reversed the inhibitory effects of CaR on O2 consumption without affecting basal O2 consumption. Our findings identified signaling elements required for CaR-mediated TNF production that are integral components regulating mTAL function via a mechanism involving COX-2 expression and PGE2 production.

NFAT regulates calcium-sensing receptor-mediated TNF production

2006 ◽  
Vol 290 (5) ◽  
pp. F1110-F1117 ◽  
Author(s):  
Huda Ismail Abdullah ◽  
Paulina L. Pedraza ◽  
Shoujin Hao ◽  
Karin D. Rodland ◽  
John C. McGiff ◽  
...  
Keyword(s):  
Extracellular Fluid ◽  
Dominant Negative ◽  
Peptide Ligand ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Calcium Sensing Receptor ◽  
Activated T Cells ◽  
Calcium Sensing ◽  
Dependent Activity ◽  
Calcineurin Activity

Because nuclear factor of activated T cells (NFAT) has been implicated in TNF production as well as osmoregulation and salt and water homeostasis, we addressed whether calcium-sensing receptor (CaR)-mediated TNF production in medullary thick ascending limb (mTAL) cells was NFAT dependent. TNF production in response to addition of extracellular Ca2+ (1.2 mM) was abolished in mTAL cells transiently transfected with a dominant-negative CaR construct (R796W) or pretreated with the phosphatidylinositol phospholipase C (PI-PLC) inhibitor U-73122. Cyclosporine A (CsA), an inhibitor of the serine/threonine phosphatase calcineurin, and a peptide ligand, VIVIT, that selectively inhibits calcineurin-NFAT signaling, also prevented CaR-mediated TNF production. Increases in calcineurin activity in cells challenged with Ca2+ were inhibited after pretreatment with U-73122 and CsA, suggesting that CaR activation increases calcineurin activity in a PI-PLC-dependent manner. Moreover, U-73122, CsA, and VIVIT inhibited CaR-dependent activity of an NFAT construct that drives expression of firefly luciferase in transiently transfected mTAL cells. Collectively, these data verify the role of calcineurin and NFAT in CaR-mediated TNF production by mTAL cells. Activation of the CaR also increased the binding of NFAT to a consensus oligonucleotide, an effect that was blocked by U-73122 and CsA, suggesting that a calcineurin- and NFAT-dependent pathway increases TNF production in mTAL cells. This mechanism likely regulates TNF gene transcription as U-73122, CsA, and VIVIT blocked CaR-dependent activity of a TNF promoter construct. Elucidating CaR-mediated signaling pathways that regulate TNF production in the mTAL will be crucial to understanding mechanisms that regulate extracellular fluid volume and salt balance.

CaR activation increases TNF production by mTAL cells via a Gi-dependent mechanism

2008 ◽  
Vol 294 (2) ◽  
pp. F345-F354 ◽  
Author(s):  
Huda Ismail Abdullah ◽  
Paulina L. Pedraza ◽  
John C. McGiff ◽  
Nicholas R. Ferreri
Keyword(s):  
Extracellular Fluid ◽  
Inhibitory Effect ◽  
Dominant Negative ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Activated T Cells ◽  
Calcium Sensing ◽  
Promoter Construct ◽  
Gf 109203X ◽  
20 Nm

We evaluated the contribution of calcium-sensing receptor (CaR)-mediated Gi-coupled signaling to TNF production in medullary thick ascending limb (mTAL) cells. A selective Gi inhibitor, pertussis toxin (PTX), but not the inactive B-oligomer binding subunit, abolished CaR-mediated increases in TNF production. The inhibitory effect of PTX was partially reversed by using an adenylate cyclase inhibitor. CaR-mediated TNF production also was partially reversed by a cAMP analog, 8-Br-cAMP. IP1 accumulation was CaR dependent and blocked by PI-PLC; partial inhibition also was observed with PTX. CaR increased calcineurin (CaN) activity by approximately threefold, and PTX prevented CaR-mediated increases in CaN activity, an nuclear factor of activated T cells (NFAT)- cis reporter construct, and a TNF promoter construct. The interaction between Gi and PKC was determined, as we previously showed that CaR-mediated TNF production was CaN and NFAT- mediated and Gq dependent. CaR activation increased PKC activity by twofold, an effect abolished by transient transfection with a dominant negative CaR construct, R796W, or pretreatment with PTX. Inhibition with the pan-specific PKC inhibitor GF 109203X (20 nM) abolished CaR-mediated increases in activity of CaN, an NFAT reporter, and a TNF promoter construct. Collectively, the data suggest that Gi-coupled signaling contributes to NFAT-mediated TNF production in a CaN- and PKC-dependent manner and may be part of a CaR mechanism to regulate mTAL function. Moreover, concurrent Gq and Gi signaling is required for CaR-mediated TNF production in mTAL cells via a CaN/NFAT pathway that is PKC dependent. Understanding CaR-mediated signaling pathways that regulate TNF production in the mTAL is crucial to defining novel mechanisms that regulate extracellular fluid volume and salt balance.

scholarly journals The Calcium-Sensing Receptor Increases Activity of the Renal NCC through the WNK4-SPAK Pathway

2018 ◽  
Vol 29 (7) ◽  
pp. 1838-1848 ◽  
Author(s):  
Silvana Bazúa-Valenti ◽  
Lorena Rojas-Vega ◽  
María Castañeda-Bueno ◽  
Jonatan Barrera-Chimal ◽  
Rocío Bautista ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Oral Administration ◽  
Apical Membrane ◽  
Hek293 Cells ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing

Background Hypercalciuria can result from activation of the basolateral calcium-sensing receptor (CaSR), which in the thick ascending limb of Henle’s loop controls Ca2+ excretion and NaCl reabsorption in response to extracellular Ca2+. However, the function of CaSR in the regulation of NaCl reabsorption in the distal convoluted tubule (DCT) is unknown. We hypothesized that CaSR in this location is involved in activating the thiazide-sensitive NaCl cotransporter (NCC) to prevent NaCl loss.Methods We used a combination of in vitro and in vivo models to examine the effects of CaSR on NCC activity. Because the KLHL3-WNK4-SPAK pathway is involved in regulating NaCl reabsorption in the DCT, we assessed the involvement of this pathway as well.Results Thiazide-sensitive 22Na+ uptake assays in Xenopus laevis oocytes revealed that NCC activity increased in a WNK4-dependent manner upon activation of CaSR with Gd3+. In HEK293 cells, treatment with the calcimimetic R-568 stimulated SPAK phosphorylation only in the presence of WNK4. The WNK4 inhibitor WNK463 also prevented this effect. Furthermore, CaSR activation in HEK293 cells led to phosphorylation of KLHL3 and WNK4 and increased WNK4 abundance and activity. Finally, acute oral administration of R-568 in mice led to the phosphorylation of NCC.Conclusions Activation of CaSR can increase NCC activity via the WNK4-SPAK pathway. It is possible that activation of CaSR by Ca2+ in the apical membrane of the DCT increases NaCl reabsorption by NCC, with the consequent, well known decrease of Ca2+ reabsorption, further promoting hypercalciuria.

scholarly journals Capsaicin, a TRPV1 Ligand, Suppresses Bone Resorption by Inhibiting the Prostaglandin E Production of Osteoblasts, and Attenuates the Inflammatory Bone Loss Induced by Lipopolysaccharide

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Megumi Kobayashi ◽  
Kenta Watanabe ◽  
Satoshi Yokoyama ◽  
Chiho Matsumoto ◽  
Michiko Hirata ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Bone Loss ◽  
Transient Receptor Potential ◽  
Interleukin 1 ◽  
Osteoclast Differentiation ◽  
Bone Diseases ◽  
Prostaglandin E ◽  
Transient Receptor Potential Vanilloid ◽  
Cox 2

Capsaicin, a transient receptor potential vanilloid type 1 (TRPV1) ligand, regulates nerve-related pain-sensitive signals, inflammation, and cancer growth. Capsaicin suppresses interleukin-1-induced osteoclast differentiation, but its roles in bone tissues and bone diseases are not known. This study examined the effects of capsaicin on inflammatory bone resorption and prostaglandin E (PGE) production induced by lipopolysaccharide (LPS) in vitro and on bone mass in LPS-treated mice in vivo. Capsaicin suppressed osteoclast formation, bone resorption, and PGE production induced by LPS in vitro. Capsaicin suppressed the expression of cyclooxygenase-2 (COX-2) and membrane-bound PGE synthase-1 (mPGES-1) mRNAs and PGE production induced by LPS in osteoblasts. Capsaicin may suppress PGE production by inhibiting the expression of COX-2 and mPGES-1 in osteoblasts and LPS-induced bone resorption by TRPV1 signals because osteoblasts express TRPV1. LPS treatment markedly induced bone loss in the femur in mice, and capsaicin significantly restored the inflammatory bone loss induced by LPS in mice. TRPV1 ligands like capsaicin may therefore be potentially useful as clinical drugs targeting bone diseases associated with inflammatory bone resorption.

scholarly journals High sodium intake increases HCO3− absorption in medullary thick ascending limb through adaptations in basolateral and apical Na+/H+ exchangers

2011 ◽  
Vol 301 (2) ◽  
pp. F334-F343 ◽  
Author(s):  
David W. Good ◽  
Thampi George ◽  
Bruns A. Watts
Keyword(s):  
Absorptive Capacity ◽  
Sodium Intake ◽  
Thick Ascending Limb ◽  
Acid Base Balance ◽  
High Sodium ◽  
High Sodium Intake ◽  
Medullary Thick Ascending Limb ◽  
Nhe1 Activity ◽  
Exchange Activity

A high sodium intake increases the capacity of the medullary thick ascending limb (MTAL) to absorb HCO3−. Here, we examined the role of the apical NHE3 and basolateral NHE1 Na+/H+ exchangers in this adaptation. MTALs from rats drinking H2O or 0.28 M NaCl for 5–7 days were perfused in vitro. High sodium intake increased HCO3− absorption rate by 60%. The increased HCO3− absorptive capacity was mediated by an increase in apical NHE3 activity. Inhibiting basolateral NHE1 with bath amiloride eliminated 60% of the adaptive increase in HCO3− absorption. Thus the majority of the increase in NHE3 activity was dependent on NHE1. A high sodium intake increased basolateral Na+/H+ exchange activity by 89% in association with an increase in NHE1 expression. High sodium intake increased apical Na+/H+ exchange activity by 30% under conditions in which basolateral Na+/H+ exchange was inhibited but did not change NHE3 abundance. These results suggest that high sodium intake increases HCO3− absorptive capacity in the MTAL through 1) an adaptive increase in basolateral NHE1 activity that results secondarily in an increase in apical NHE3 activity; and 2) an adaptive increase in NHE3 activity, independent of NHE1 activity. These studies support a role for NHE1 in the long-term regulation of renal tubule function and suggest that the regulatory interaction whereby NHE1 enhances the activity of NHE3 in the MTAL plays a role in the chronic regulation of HCO3− absorption. The adaptive increases in Na+/H+ exchange activity and HCO3− absorption in the MTAL may play a role in enabling the kidneys to regulate acid-base balance during changes in sodium and volume balance.

scholarly journals Monophosphoryl lipid A induces protection against LPS in medullary thick ascending limb through a TLR4-TRIF-PI3K signaling pathway

2017 ◽  
Vol 313 (1) ◽  
pp. F103-F115 ◽  
Author(s):  
Bruns A. Watts ◽  
Thampi George ◽  
Edward R. Sherwood ◽  
David W. Good
Keyword(s):  
Bacterial Infections ◽  
Lipid A ◽  
Thick Ascending Limb ◽  
Akt Inhibitor ◽  
Erk Activation ◽  
Akt Phosphorylation ◽  
Medullary Thick Ascending Limb ◽  
Monophosphoryl Lipid A ◽  
Monophosphoryl Lipid

Monophosphoryl lipid A (MPLA) is a detoxified derivative of LPS that induces tolerance to LPS and augments host resistance to bacterial infections. Previously, we demonstrated that LPS inhibits [Formula: see text] absorption in the medullary thick ascending limb (MTAL) through a basolateral Toll-like receptor 4 (TLR4)-myeloid differentiation factor 88 (MyD88)-ERK pathway. Here we examined whether pretreatment with MPLA would attenuate LPS inhibition. MTALs from rats were perfused in vitro with MPLA (1 µg/ml) in bath and lumen or bath alone for 2 h, and then LPS was added to (and MPLA removed from) the bath solution. Pretreatment with MPLA eliminated LPS-induced inhibition of [Formula: see text] absorption. In MTALs pretreated with MPLA plus a phosphatidylinositol 3-kinase (PI3K) or Akt inhibitor, LPS decreased [Formula: see text] absorption. MPLA increased Akt phosphorylation in dissected MTALs. The Akt activation was eliminated by a PI3K inhibitor and in MTALs from TLR4−/−or Toll/IL-1 receptor domain-containing adaptor-inducing IFN-β (TRIF)−/−mice. The effect of MPLA to prevent LPS inhibition of [Formula: see text] absorption also was TRIF dependent. Pretreatment with MPLA prevented LPS-induced ERK activation; this effect was dependent on PI3K. MPLA alone had no effect on [Formula: see text] absorption, and MPLA pretreatment did not prevent ERK-mediated inhibition of [Formula: see text] absorption by aldosterone, consistent with MPLA's low toxicity profile. These results demonstrate that pretreatment with MPLA prevents the effect of LPS to inhibit [Formula: see text] absorption in the MTAL. This protective effect is mediated directly through MPLA stimulation of a TLR4-TRIF-PI3K-Akt pathway that prevents LPS-induced ERK activation. These studies identify detoxified TLR4-based immunomodulators as novel potential therapeutic agents to prevent or treat renal tubule dysfunction in response to bacterial infections.

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