High water intake induces primary cilium elongation in renal tubular cells

The primary cilium protrudes from the cell surface and functions as a mechanosensor. Recently, we found that water intake restriction shortens the primary cilia of renal tubular cells, and a blockage of the shortening disturbs the ability of the kidneys to concentrate urine. Here, we investigate whether high water intake (HWI) alters primary cilia length, and if so, what is its underlying mechanism and its role on kidney urine production. Methods: Experimental mice were given free access to normal water (normal water intake) or 3% sucrose-containing water for HWI for 2 days. Some mice were administered with U0126 (10 mg/kg body weight), an inhibitor of MEK kinase, from 2 days before HWI, daily. The primary cilium length and urine amount and osmolality were investigated. Results: HWI-induced diluted urine production and primary cilium elongation in renal tubular cells. HWI increased the expression of α-tubulin acetyltransferase 1 (αTAT1), leading to the acetylation of α-tubulins, a core protein of the primary cilia. HWI also increased phosphorylated ERK1/2 (p-ERK1/2) and exocyst complex component 5 (Exoc5) expression in the kidneys. U0126 blocked HWI-induced increases in αTAT1, p-ERK1/2, and Exoc5 expression. U0126 inhibited HWI-induced α-tubulin acetylation, primary cilium elongation, urine amount increase, and urine osmolality decrease. Conclusion: These results show that increased water intake elongates the primary cilia via ERK1/2 activation and that ERK inhibition prevents primary cilium elongation and diluted urine production. These data suggest that the elongation of primary cilium length is associated with the production of diluted urine.

Shortening of primary cilia length is associated with urine concentration in the kidneys

The primary cilium, a microtubule-based cellular organelle present in certain kidney cells, functions as a mechano-sensor to monitor fluid flow in addition to various other biological functions. In kidneys, the primary cilia protrude into the tubular lumen and are directly exposed to pro-urine flow and components. However, their effects on urine concentration remain to be defined. Here, we investigated the association between primary cilia and urine concentration. Methods: Mice either had free access to water (normal water intake, NWI) or were not allowed access to water (water deprivation, WD). Some mice received tubastatin, an inhibitor of histone deacetylase 6 (HDAC6), which regulates the acetylation of α-tubulin, a core protein of microtubules. Results: WD decreased urine output and increased urine osmolality, concomitant with apical plasma membrane localization of aquaporin 2 (AQP2) in the kidney. After WD, compared with after NWI, the lengths of primary cilia in renal tubular epithelial cells were shortened and HDAC6 activity increased. WD induced deacetylation of α-tubulin without altering α-tubulin levels in the kidney. Tubastatin prevented the shortening of cilia through increasing HDAC6 activity and consequently increasing acetylated α-tubulin expression. Furthermore, tubastatin prevented the WD-induced reduction of urine output, urine osmolality increase, and apical plasma membrane localization of AQP2. Conclusions: WD shortens primary cilia length through HDAC6 activation and α-tubulin deacetylation, while HDAC6 inhibition blocks the WD-induced changes in cilia length and urine output. This suggests that cilia length alterations are involved, at least in part, in the regulation of body water balance and urine concentration.

Electrophysiological Properties of Ion Channels in Ascaris suum Tissue Incorporated into Planar Lipid Bilayers

Ion channels are important targets of anthelmintic agents. In this study, we identified 3 types of ion channels in Ascaris suum tissue incorporated into planar lipid bilayers using an electrophysiological technique. The most frequent channel was a large-conductance cation channel (209 pS), which accounted for 64.5% of channels incorporated (n=60). Its open-state probability (Po) was ~0.3 in the voltage range of –60~+60 mV. A substate was observed at 55% of the main-state. The permeability ratio of Cl- to K+ (PCl/PK) was ~0.5 and PNa/PK was 0.81 in both states. Another type of cation channel was recorded in 7.5% of channels incorporated (n=7) and discriminated from the large-conductance cation channel by its smaller conductance (55.3 pS). Its Po was low at all voltages tested (~0.1). The third type was an anion channel recorded in 27.9% of channels incorporated (n=26). Its conductance was 39.0 pS and PCl/PK was 8.6±0.8. Po was ~1.0 at all tested potentials. In summary, we identified 2 types of cation and 1 type of anion channels in Ascaris suum. Gating of these channels did not much vary with voltage and their ionic selectivity is rather low. Their molecular nature, functions, and potentials as anthelmintic drug targets remain to be studied further.

IDH2 gene deficiency accelerates unilateral ureteral obstructioninduced kidney inflammation through oxidative stress and activation of macrophages

Mitochondrial NADP+-dependent isocitrate dehydrogenase 2 (IDH2) produces NADPH, which is known to inhibit mitochondrial oxidative stress. Ureteral obstruction induces kidney inflammation and fibrosis via oxidative stress. Here, we investigated the role and underlying mechanism of IDH2 in unilateral ureteral obstruction (UUO)-induced kidney inflammation using IDH2 gene deleted mice (IDH2–/–). Eight- to 10-week-old female IDH2–/– mice and wild type (IDH2+/+) littermates were subjected to UUO and kidneys were harvested 5 days after UUO. IDH2 was not detected in the kidneys of IDH2–/– mice, while UUO decreased IDH2 in IDH2+/+ mice. UUO increased the expressions of markers of oxidative stress in both IDH2+/+ and IDH2–/– mice, and these changes were greater in IDH2–/– mice compared to IDH2+/+ mice. Bone marrow-derived macrophages of IDH2–/– mice showed a more migrating phenotype with greater ruffle formation and Rac1 distribution than that of IDH2+/+ mice. Correspondently, UUO-induced infiltration of monocytes/macrophages was greater in IDH2–/– mice compared to IDH2+/+ mice. Taken together, these data demonstrate that IDH2 plays a protective role against UUO-induced inflammation through inhibition of oxidative stress and macrophage infiltration.

Electrophysiological Properties of Ion Channels in Ascaris suum Tissue Incorporated into Planar Lipid Bilayers

Ion channels are important targets of anthelmintic agents. In this study, we identified 3 types of ion channels in Ascaris suum tissue incorporated into planar lipid bilayers using an electrophysiological technique. The most frequent channel was a large-conductance cation channel (209 pS), which accounted for 64.5% of channels incorporated (n=60). Its open-state probability (Po) was ~0.3 in the voltage range of –60~+60 mV. A substate was observed at 55% of the main-state. The permeability ratio of Cl- to K+ (PCl/PK) was ~0.5 and PNa/PK was 0.81 in both states. Another type of cation channel was recorded in 7.5% of channels incorporated (n=7) and discriminated from the large-conductance cation channel by its smaller conductance (55.3 pS). Its Po was low at all voltages tested (~0.1). The third type was an anion channel recorded in 27.9% of channels incorporated (n=26). Its conductance was 39.0 pS and PCl/PK was 8.6±0.8. Po was ~1.0 at all tested potentials. In summary, we identified 2 types of cation and 1 type of anion channels in Ascaris suum. Gating of these channels did not much vary with voltage and their ionic selectivity is rather low. Their molecular nature, functions, and potentials as anthelmintic drug targets remain to be studied further.

IDH2 gene deficiency accelerates unilateral ureteral obstructioninduced kidney inflammation through oxidative stress and activation of macrophages

Mitochondrial NADP+-dependent isocitrate dehydrogenase 2 (IDH2) produces NADPH, which is known to inhibit mitochondrial oxidative stress. Ureteral obstruction induces kidney inflammation and fibrosis via oxidative stress. Here, we investigated the role and underlying mechanism of IDH2 in unilateral ureteral obstruction (UUO)-induced kidney inflammation using IDH2 gene deleted mice (IDH2–/–). Eight- to 10-week-old female IDH2–/– mice and wild type (IDH2+/+) littermates were subjected to UUO and kidneys were harvested 5 days after UUO. IDH2 was not detected in the kidneys of IDH2–/– mice, while UUO decreased IDH2 in IDH2+/+ mice. UUO increased the expressions of markers of oxidative stress in both IDH2+/+ and IDH2–/– mice, and these changes were greater in IDH2–/– mice compared to IDH2+/+ mice. Bone marrow-derived macrophages of IDH2–/– mice showed a more migrating phenotype with greater ruffle formation and Rac1 distribution than that of IDH2+/+ mice. Correspondently, UUO-induced infiltration of monocytes/macrophages was greater in IDH2–/– mice compared to IDH2+/+ mice. Taken together, these data demonstrate that IDH2 plays a protective role against UUO-induced inflammation through inhibition of oxidative stress and macrophage infiltration.

Hydrogen sulfide, a gaseous signaling molecule, elongates primary cilia on kidney tubular epithelial cells by activating extracellular signal-regulated kinase

Primary cilia on kidney tubular cells play crucial roles in maintaining structure and physiological function. Emerging evidence indicates that the absence of primary cilia, and their length, are associated with kidney diseases. The length of primary cilia in kidney tubular epithelial cells depends, at least in part, on oxidative stress and extracellular signal-regulated kinase 1/2 (ERK) activation. Hydrogen sulfide (H2S) is involved in antioxidant systems and the ERK signaling pathway. Therefore, in this study, we investigated the role of H2S in primary cilia elongation and the downstream pathway. In cultured Madin-Darby Canine Kidney cells, the length of primary cilia gradually increased up to 4 days after the cells were grown to confluent monolayers. In addition, the expression of H2S-producing enzyme increased concomitantly with primary cilia length. Treatment with NaHS, an exogenous H2S donor, accelerated the elongation of primary cilia whereas DL-propargylglycine (a cystathionine γ-lyase inhibitor) and hydroxylamine (a cystathionine-β-synthase inhibitor) delayed their elongation. NaHS treatment increased ERK activation and Sec10 and Arl13b protein expression, both of which are involved in cilia formation and elongation. Treatment with U0126, an ERK inhibitor, delayed elongation of primary cilia and blocked the effect of NaHS-mediated primary cilia elongation and Sec10 and Arl13b upregulation. Finally, we also found that H 2 S accelerated primary cilia elongation after ischemic kidney injury. These results indicate that H2S lengthens primary cilia through ERK activation and a consequent increase in Sec10 and Arl13b expression, suggesting that H2S and its downstream targets could be novel molecular targets for regulating primary cilia.

Can Tissue Cilia Lengths and Urine Cilia Proteins Be Markers of Kidney Diseases? / 전남의대학술지

The primary cilium is an organelle which consists of a microtubule in the core and a surrounding cilia membrane, and has long been recognized as a “vestigial organelle”. However, new evidence demonstrates that the primary cilium has a notable effect on signal transduction in the cell and is associated with some genetic and non-genetic diseases. In the kidney, the primary cilium protrudes into the Bowman's space and the tubular lumen from the apical side of epithelial cells. The length of primary cilia is dynamically altered during the normal cell cycle, being shortened by retraction into the cell body at the entry of cell division and elongated at differentiation. Furthermore, the length of primary cilia is also dynamically changed in the cells, as a result and/or cause, during the progression of various kidney diseases including acute kidney injury and chronic kidney disease. Notably, recent data has demonstrated that the shortening of the primary cilium in the cell is associated with fragmentation, apart from retraction into the cell body, in the progression of diseases and that the fragmented primary cilia are released into the urine. This data reveals that the alteration of primary cilia length could be related to the progression of diseases. This review will consider if primary cilia length alteration is associated with the progression of kidney diseases and if the length of tissue primary cilia and the presence or increase of cilia proteins in the urine is indicative of kidney diseases.

Experimental evidence that preexisting chronic kidney disease is a risk factor for acute kidney injury

No abstract available.

Intra-renal slow cell-cycle cells contribute to the restoration of kidney tubules injured by ischemia/reperfusion / 대한해부학회지

Renal epithelial cells damaged by ischemia/reperfusion (I/R) can be restored by timely and appropriate treatment. Recent studies have reported that intra renal adult kidney stem cells contribute to the restoration of tubules damaged by I/R. Here, we determined the role of adult tubular cells in the restoration of damaged tubules. We labeled slow cell-cycle cells (SCCs) with 5-bromo-2'-deoxyuridine (BrdU) and investigated their location in the kidneys as well as their contribution to the restoration of tubular cells damaged by I/R injury in mice. Thirty minutes of bilateral ischemia resulted in severe disruption of tubular epithelial cells along with a decline in renal function. The post-ischemic disruption of tubular epithelial cells was most severe in the S3 segment of the outer stripe of the outer medulla. Damaged tubules demonstrated gradual recovery of renal function over time. BrdU-labeled SCCs were mainly observed in tubules located at the junction of cortex and outer medulla, as well as in the inner medulla. The tubular SCCs expressed functional tubule cell markers such as Na/K-ATPase, Na-K-Cl cotransporter-2, and aquaporin 1 and 2. BrdU-labeled SCCs survived I/R injury and proliferated. These results demonstrate that SCCs present in tubules contribute to the restoration of tubular epithelial cells injured by I/R.

17beta-estradiol Attenuates Renal Fibrosis in Mice with Obstructive Uropathy

PURPOSE: Men are generally more prone to chronic renal disease and progression to end stage renal disease than women. The purpose of this study is to prove the effect of gender and sex hormone on renal fibrosis in mice with unilateral ureteral obstruction (UUO) and to elucidate the specific underlying mechanisms. METHODS: We compared the expression of alpha-smooth muscle actin (alpha-SMA) in female and male mice with complete UUO (day 7). After this, we estimated the changes of renal fibrosis in the female mice with oophorectomy and in the female mice with oophorectomy and replacement of 17beta-estradiol, respectively. RESULTS: The level of alpha-SMA in the female kidney with UUO was significantly lower than that in the male kidney with UUO. oophorectomy and replacement of 17beta-estradiol did not change the expression of angiotensin II type 1 (AT1) receptor in the female kidney with UUO, whereas the expression of angiotensin II type 2 (AT2) receptor was significantly more elevated in the intact female (IF) and the oophorectomized female with estrogen (OF+E) than that in the oophorectomized female (OF). The expressions of inducible nitric oxide synthase (iNOS) in the IF and OF+E mice were significantly more elevated than that in the OF mice, which was similar to the expression of AT2 receptor. CONCLUSION: The female gender is associated with resistance to renal fibrosis in obstructive uropathy and this gender difference may originate from the existence of 17beta-estradiol, which has an anti-fibrotic effect via upregulation of the AT2 receptor and iNOS.

Kidney Tubular Cell Regeneration Starts in the Deep Cortex after Ischemia / 대한신장학회지

PURPOSE: In kidneys exposed to ischemia/reperfusion (I/R), the periodic and regional changes of loss and restoration of tubular epithelial cells and the influence of these processes for renal function remain to be defined. We investigated the loss and regeneration of tubular cells in each nephron segment at various times after I/R. METHODS: Mice were subjected to 30 min of bilateral renal ischemia and were administered 5-bromo-2'-deoxyuridine (BrdU) 20 hours before harvest kidneys. The numbers of tubular cell nuclei, BrdUincorporating cells and proliferative cell nuclear antigen (PCNA)-positive cells were analyzed by PASstaining and immunohistochemistry. RESULTS: Thirty minutes of ischemia induced loss of tubular epithelial cells in the outer stripe of the outer medulla. The loss of tubular epithelial cells peaked 24 hours after ischemia. After the maximum decrease, recovery of number of tubular epithelial cells was observed from 3 days after I/R in the outer medulla and from 5 days in the cortex. The tubular cell numbers were inversely correlated with the changes in concentrations of plasma creatinine and BUN by Pearson correlation, indicating that the decrease and increase of tubular epithelial cell numbers reflect functional failure and recovery, respectively. Cell proliferation as determined by BrdU-incorporating appeared in the deep cortex from 3 days after ischemia. CONCLUSION: The recovery of renal function was found to significantly correlate with the restoration of tubular cells. Furthermore, the regeneration of tubular cells started in the tubules of the deep cortex, suggesting that it may be a great proliferative cell niche.

Spatiotemporal regulation of fibroblast growth factor signal blocking for endoderm formation in Xenopus laevis

We have previously shown that the inhibition of fibroblast growth factor (FGF) signaling induced endodermal gene expression in the animal cap and caused the expansion of the endodermal mass in Xenopus embryos. However, we still do not know whether or not the alteration of FGF signaling controls embryonic cell fate, or when FGF signal blocking is required for endoderm formation in Xenopus. Here, we show that FGF signal blocking in embryonic cells causes their descendants to move into the endodermal region and to express endodermal genes. It is also interesting that blocking FGF signaling between fertilization and embryonic stage 10.5 promotes endoderm formation, but persistent FGF signaling blocking after stage 10.5 restricts endoderm formation and differentiation.

Locations of Slow-Cycling Cells, Adult Stem Cells, in the Organs of Adult Mouse / 대한해부학회지

Adult stem cells possess the characteristics of self-renewal, multipotent, plasticity as well as slow cycling rate. We investigated a location of slow-cycling cells, that is, adult stem-like cells, in various organs in the 8 week-old mice which administered bromodeoxyuridine (BrdU) at neonatal phase. BrdU-retaining cells (slow-cycling cells) were observed in speramtogonia at the edge of seminiferous tubules in testes, hair root cells surrounding hair follicles, the cells in the inner nuclear layer of the retina, the myocytes in the hearts, the cells in the parenchyma and the Glisson's capsule of liver, the cells in the epithelial layer of bronchioles, and the tubular epithelial cells in the kidneys. In conclusion, various organs of adult mouse expressed slow-cycling cells, indicating that the cells may associate with normal cell turnover and repair after damages.

Screening of Interacting Proteins with PV.1 as Downstream Factors of BMP Signal / 대한해부학회지

Homeodomain transcription factors functioning downstream of BMP ventral pathway have been reported to share similar domain of roles in mesoderm patterning along the dorsal-ventral axis. To elucidate the differential role of PV.1 in the aspect of relationship between dorsal and ventral region, we tried to screen PV.1- interacting proteins. Twenty-four PV.1-interacting proteins were identified by yeast two-hybrid screening. Xvent-2 and Xclaudin-6 among these, went under domain study. The C-terminus of PV.1, more specifically 197-241 region was found to interact with Xclaudin-6. Meanwhile Xvent-2 has mild affinity to overall C-terminal region of PV.1. At the same time it was found that Xvent-2 homodimerizes and also binds to Xclaudin-6.

Catechins inhibit angiotensin II-induced vascular smooth muscle cell proliferation via mitogen-activated protein kinase pathway

Catechins, components of green tea, reduce the incidence of cardiovascular diseases such as atherosclerosis. Angiotensin II (Ang II) is highly implicated in the proliferation of vascular smooth muscle cells (VSMC), resulting in atherosclerosis. The acting mechanisms of the catechins remain to be defined in the proliferation of VSMC induced by Ang II. Here we report that catechin, epicatechin (EC), epicatechingallate (ECG) or epigallocatechingallate (EGCG) significantly inhibits the Ang II-induced [3H]thymidine incorporation into the primary cultured rat aortic VSMC. Ang II increases the phosphorylation of the extracellular signal-regulated protein kinase 1/2 (ERK 1/2), c-jun-N-terminal kinase 1/2 (JNK 1/2), or p38 mitogen-activated protein kinases (MAPKs) and mRNA expression of c-jun and c-fos. The EGCG pretreatment inhibits the Ang II-induced phosphorylation of ERK 1/2, JNK 1/2, or p38 MAPK, and the expression of c-jun or c-fos mRNA. U0126, a MEK inhibitor, SP600125, a JNK inhibitor, or SB203580, a p38 inhibitor, attenuates the Ang II-induced [3H]thymidine incorporation into the VSMC. In conclusion, catechins inhibit the Ang II-stimulated VSMC proliferation via the inhibition of the Ang II-stimulated activation of MAPK and activator protein-1 signaling pathways. The antiproliferative effect of catechins may be associated with the reduced risk of cardiovascular diseases by the intake of green tea. Catechins may be useful in the development of prevention and therapeutics of vascular diseases.

Renal Fibrosis Induced by the Partial Reduction of the Diameter of Renal Artery in Mouse / 대한해부학회지

Kidney artery stenosis such as atherosclerosis induces ischemic nephropathy which is caused by the reduction of blood supply to the kidneys. Since useful experimental animal models for the kidney artery stenosis is very limited, the pathophysiology of the ischemic nephropathy induced by the renal artery stenosis remain to be defined. In the present studies, I developed the mouse experimental model of kidney artery stenosis by the reduction of renal artery diameter to the out side diameter of 31-guage needle.The reduction of renal artery diameter reduces kidney size and mass. There is the severe shrink of glomeruli, tubular atrophy and infiltration of l eukocytes. In the kidney subjected to the experiment of the reduction of renal artery diameter. The expression of alpha-smooth muscle actin in the kidney partially tied the renal artery is much greater than that in the contralateral kidney. These results demonstrate that the reduction of renal artery diameter induced renal fibrosis, the reduction of renal blood flow and kidney size and that the experimental models may be useful to study the pathophysiology of ischemic nephropathy induced by renal artery stenosis as well as chronic renal failure which is involved in renal fibrotic responses.

A Role of Mitogen Activated Protein Kinases and Inflammatory Responses in Gender Differences in Kidney Ischemia Injury

It is not known whether gender differences play a role in susceptibility to ischemic acute renal failure. Thus, we examined if there were any differences in susceptibility between male and female mice to kidney ischemic injury, and if so, whether it is due to differences in mitogen activated protein kinases (MAPKs) or inflammatory responses to ischemia. Female mice were protected against kidney ischemia when compared with males. Thirty minutes of bilateral ischemia resulted in marked functional and morphological damages in males, but not in females. The ischemia-induced phosphorylation of c-jun N-terminal stress-activated protein kinases (JNKs) was higher in males than in females. Phosphorylation of extracellular signal-regulated kinases (ERKs) was lower in males than in females. Post- ischemia medullary infiltration of RAW 264.7 cell, a monocyte-macrophage cell, and intercellular adhesion molecule-1 (ICAM-1) were greater in males than in females. In conclusion, males were much more susceptible to ischemia than females. The enhanced propensity to ischemic injury in males was correlated with greater activation of JNKs, greater expression of ICAM-1, and greater trapping of leukocytes in the medulla.

Prior Ischemic Treatment Renders Kidney Resistant to Subsequent Ischemia

Prior ischemia leads to resistance against subsequent ischemic insults. The mechanisms that underlie this adaptive response remain unidentified. Thus, we studied whether the reduced susceptibility of mice previously subjected to the ischemia to ischemia/ reperfusion injury is related with altered inflammatory responses. Thirty minutes of bilateral kidney ischemia results in significantly increased plasma creatinine and blood urea nitrogen levels in BALB/c male mice. There is severe disruption of actin cytoskeleton of proximal tubular cells in the outer stripe of the outer medulla 24 hours post-ischemia. When mice are subjected to 30 minutes of bilateral ischemia 8 days later, there is no increase in plasma creatinine and blood urea nitrogen levels and the post-ischemic disruption of actin cytoskeleton of proximal tubular cells is much less. Inflammatory responses have highly implicated with ischemia/reperfusion injury. Ischemia results in the increased tissue myeloperoxidase (MPO) activity that is a marker of leukocyte infiltration. There is, however, no the post-ischemic increase of MPO activity in kidneys previously subjected to ischemia. Post-ischemic expression of tissue intercellular adhesion molecule-1 (ICAM-1) is greater in the kidney previously sham-operated than in the kidneys previously subjected to ischemia. In conclusion, prior ischemia protects kidney function and morphology against subsequent ischemia 8 days later. The resistance is associated with the reduced post-ischemic leukocyte infiltration due to the reduced post-ischemic ICAM-1 expression.

Role of phospholipase A2 in oxidant-induced alteration in phosphate transport in primary cultured rabbit renal proximal tubule cells

The present study was undertaken to examine the role of phospholipase A2 (PLA2) in oxidant-induced inhibition of phosphate transport in primary cultured rabbit renal proximal tubule cells. Uptakes of phosphate and glucose were dose-dependently inhibited by an oxidant t-butylhydroperoxide (tBHP), and the significant inhibition appeared at 0.025 mM of tBHP, whereas tBHP-induced alterations in lipid peroxidation and cell viability were seen at 0.5 mM. tBHP stimulated arachidonic acid (AA) release in a dose-dependent fashion. A PLA2 inhibitor mepacrine prevented tBHP-induced AA release, but it did not alter the inhibition of phosphate uptake and the decrease in cell viability induced by tBHP. tBHP-induced inhibition of phosphate transport was not affected by a PKC inhibitor, staurosporine. tBHP at 0.1 mM did not produce the inhibition of Na+-K+-ATPase activity in microsomal fraction, although it significantly inhibited at 1.0 mM. These results suggest that tBHP can inhibit phosphate uptake through a mechanism independent of PLA2 activation, irreversible cell injury, and lipid peroxidation in primary cultured rabbit renal proximal tubular cells.