The ability to remember the relationship between unrelated events is a powerful cognitive function. When two unrelated stimuli are encoded in a condition of high level of unitization (LOU), the associative memory could be acquired with a strong familiarity contribution. This provides a promising way for brain lesioned patients to obtain a new associative memory. However, recent studies are inconsistent on the extent to which the recollection process is involved in unitized associative memory. To clarify this issue, two groups of participants learned unrelated word pairs once or twice in the high- and low-LOU conditions and were tested at 10 min and 24 h. The recollection and familiarity processes were estimated by dual-process models. Results showed that both recollection and familiarity were stronger for the high- than for the low-LOU condition. However, when memory strength was controlled, recollection was comparable for high- and low-LOU conditions, while familiarity still showed a significant effect of LOU. In addition, the effect of LOU for familiarity increased after repetition learning. The results suggest that the recollection contribution to unitized association is related to memory strength, but the familiarity contribution is stably observed and increases after repetition learning when unrelated word pairs are used. These findings are also significant for memory rehabilitation in aging and brain lesioned patients.

IntroductionRetrieval practice with answer feedback is an efficient way to enhance episodic memory, but previous studies fail to find a robust transfer of learning for non-trained information. The aim of this study was to clarify the boundary conditions for the transfer effect after answer feedback.MethodsTwo groups of participants learned episodic sentences through single or repeated study and training (ST, SSTT), then they were tested at 10 min, 1 day and 1 week. During the training phase, only half of the items were trained under conditions of feedback, no feedback, or restudy, while the other half items were not trained.ResultsThe transfer effect (i.e., feedback vs. restudy condition for the non-trained items) was influenced by the interaction of repetition and retention interval, as it appeared at 10 min after SSTT but not after ST. Moreover, the transfer effect declined over time, and was significantly lower than chance level at 1 week after SSTT.DiscussionThe results suggest that the transfer effect after answer feedback could be obtained after repeated study and training for the episodic information, but it is short-lived. They also highlight the time change of memory specificity and generalization due to answer feedback.

There are at least eight aquaporins (AQPs) expressed in the kidney. Including AQP1 expressed in proximal tubules, thin descending limb of Henle and vasa recta; AQP2, AQP3, AQP4, AQP5, and AQP6 expressed in collecting ducts; AQP7 expressed in proximal tubules; AQP8 expressed in proximal tubules and collecting ducts; and AQP11 expressed in the endoplasmic reticulum of proximal tubular epithelial cells. Over years, researchers have constructed different AQP knockout mice and explored the effect of AQP knockout on kidney function. Thus, the roles of AQPs in renal physiology are revealed, providing very useful information for addressing fundamental questions about transepithelial water transport and the mechanism of near isoosmolar fluid reabsorption. This chapter introduces the localization and function of AQPs in the kidney and their roles in different kidney diseases to reveal the prospects of AQPs in further basic and clinical studies.

How memory representations are eventually established and maintained in the brain is one of central issues in memory research. Although the hippocampus and various brain regions have been shown to be involved in learning and memory, how they coordinate to support successful memory through errors is unclear. In this study, a retrieval practice (RP) - feedback (FB) paradigm was adopted to address this issue. Fifty-six participants (27 in the behavioral group, and 29 in the fMRI group) learned 120 Swahili-Chinese words associations and underwent two RP-answer FB cycles (i.e., RP1, FB1, RP2, FB2). The responses of the fMRI group were recorded in the fMRI scanner. The trials were divided based on participant's performance (correct or incorrect, C or I) during the two RPs and the final test (i.e., trial type, CCC, ICC, IIC III). The results showed that the regions in the salience and executive control networks (S-ECN) during RP, but not during FB, was strongly predictive of final successful memory. Their activation was just before the errors were corrected (i.e., RP1 in ICC trials and RP2 in IIC trials). The anterior insula (AI) is a core region in monitoring repeated errors, and it had differential connectivity with the default mode network (DMN) regions and the hippocampus during the RP and FB phases to inhibit incorrect answers and update memory. In contrast, maintaining corrected memory representation requires repeated RP and FB, which was associated with the DMN activation. Our study clarified how different brain regions support error monitoring and memory maintenance through repeated RP and FB, and emphasized the role of the insula in learning from errors.

Many studies have shown that compared to the restudy condition (RS), retrieval practice (RP) enhances the long-retention memory of retrieved items (i.e., the testing effect), and facilitates later memory of non-retrieved but related items (i.e., the transfer effect). However, previous studies have usually used repeated study and repeated testing, which are included in study-testing cycles. Therefore, it is unclear to what extent the factors of repeated study and repeated testing influence testing and transfer effects over time. In this study, participants studied sentences that described various episodes, then tested a half subset of the original sentences under three conditions (RP, RS, control). After retention intervals of 10 min, 1 day and 7 days, they recalled all of the information in the sentences. The results showed that the testing effect was enhanced by repeated study or repeated testing, while the transfer effect occurred only after both repeated study and repeated testing. Furthermore, repeated study or repeated testing slowed down the forgetting of retrieved items, while the forgetting of non-retrieved items occurred after both repeated study and repeated testing. The testing effect increased over time, but the transfer effect remained relatively stable over time. These results clarified different roles of multiple study repetitions and testing opportunities in the testing effect and the transfer effect, and suggest that the repeated retrieval could be combined with repeated study to optimally promote long-term retention of the memory of tested and non-tested items.

Previous studies have shown that the ventral medial prefrontal cortex (vmPFC) plays an important role in schema-related memory. However, there is an intensive debate to what extent the activation of subregions of the hippocampus is involved in retrieving schema-related memory. In addition, it is unclear how the functional connectivity (FC) between the vmPFC and the hippocampus, as well as the connectivity of the vmPFC with other regions, are modulated by prior knowledge (PK) during memory retrieval over time. To address these issues, participants learned paragraphs that described features of each unfamiliar word from familiar and unfamiliar categories (i.e., high and low PK conditions) 20 min, 1 day, and 1 week before the test. They then performed a recognition task to judge whether the sentences were old in the scanner. The results showed that the activation of the anterior-medial hippocampus (amHPC) cluster was stronger when the old sentences with high (vs. low) PK were correctly retrieved. The activation of the posterior hippocampus (pHPC) cluster, as well as the vmPFC, was stronger when the new sentences with high (vs. low) PK were correctly rejected (i.e., CR trials), whereas the cluster of anterior-lateral hippocampus (alHPC) showed the opposite. The FC of the vmPFC with the amHPC and perirhinal cortex/inferior temporal gyrus was stronger in the high (vs. low) PK condition, whereas the FC of the vmPFC with the alHPC, thalamus and frontal regions showed the opposite for the CR trials. This study highlighted that different brain networks, which were associated with the vmPFC, subregions of the hippocampus and cognitive control regions, were responsible for retrieving the information with high and low PK.

Feedback is an important factor to enhance subsequent memory, showing that memory performance increases after the feedback than after the no feedback condition during retrieval practice. However, most studies have provided answers as feedback and only examined memory accuracy. It is unclear whether memory is enhanced over time when other types of feedback (e.g., correct/incorrect) is given. In addition, during retrieval practice, participants' responses differ in correctness and confidence level. To what extent these initial memory features interact with feedback type to influence subsequent memory accuracy and confidence level remains unclear. In this study, to address these questions, participants learned a series of sentences, then during the retrieval practice phase, different types of feedback-feedback with correct/incorrect and answer (CA-feedback), feedback with answer (A-feedback), feedback with correct/incorrect (C-feedback), and no feedback-were given after they performed a cued-recall test and rated the confidence. After retention intervals of 5 min, 1 day, and 7 days, they took final tests, followed by the confidence rating. The results showed that different types of feedback influenced subsequent memory and forgetting by different mechanisms. The CA-feedback and A-feedback enhanced memory performance by correcting initial errors and increasing the confidence of correct trials, but the corrected memory was more easily forgotten from 5 min to 7 days. Compared to A-feedback, the CA-feedback maintained the corrected memory after 1 day. The C-feedback did not correct initial errors but slowed the forgetting rate and reduced the confidence of incorrect trials. This study highlighted the interaction between feedback type and initial memory features (correctness, confidence) to influence subsequent memory performance, including memory accuracy and confidence level.

目的 观察两种不同波长氪离子激光治疗非增殖期重度糖尿病视网膜病变(NPDR)的效果.方法 选取2016年8月至2019年1月确诊为NPDR需行全视网膜激光光凝术(PRP)治疗的糖尿病患者40例(80眼)作为研究对象,将40例患者随机采用氪黄、氪绿ELLEX激光仪治疗,分别为氪黄激光组和氪绿激光组,比较两组的治疗效果.结果 氪黄激光组、氪绿激光组患者治疗后总有效率分别为87.5％、92.5％,两组间治疗的有效率差异无统计学意义(P>0.05),两组治疗后双眼最佳矫正视力(BCVA)水平均高于治疗前(P均<0.05).氪绿激光组患者治疗后出现黄斑前膜2例.结论 采用氪黄、氪绿激光行PRP治疗均可有效控制甚至改善NPDR病变,不排除视网膜激光治疗有诱发继发性黄斑前膜的可能性.

Human autosomal dominant polycystic kidney disease (ADPKD) is characterized by bilateral renal cysts that lead to a decline in kidney function. Previous studies reported aquaporin (AQP)-3 expression in cysts derived from collecting ducts in ADPKD. To study the role of AQP3 in cyst development, we generated 2 polycystic kidney disease (PKD) mouse models: kidney-specific Pkd1 knockout mice and inducible Pkd1 knockout mice, each without and with AQP3 deletion. In both models, kidney sizes and cyst indexes were significantly reduced in AQP3-null PKD mice compared with AQP3-expressing PKD mice, with the difference seen mainly in collecting duct cysts. AQP3-deficient kidneys showed significantly reduced ATP content, increased phosphorylated (p)-AMPK, and decreased p-ERK and p-mammalian target of rapamycin (mTOR). In a matrix-grown Madin-Darby canine kidney cyst model, AQP3 expression promoted cyst enlargement and was associated with increased expression of hypoxia-inducible factor 1-α and glucose transporter 1 and increased glucose uptake. Our data suggest that the slowed renal cyst enlargement in AQP3 deficiency involves impaired energy metabolism in the kidney through AMPK and mTOR signaling and impaired cellular glucose uptake. These findings implicate AQP3 as a novel determinant of renal cyst enlargement and hence a potential drug target in ADPKD.-Wang, W., Geng, X., Lei, L., Jia, Y., Li, Y., Zhou, H., Verkman, A. S., Yang, B. Aquaporin-3 deficiency slows cyst enlargement in experimental mouse models of autosomal dominant polycystic kidney disease.

Background: Urea, the end product of protein metabolism, has been considered to have negligible toxicity for a long time. Our previous study showed a depression phenotype in urea transporter (UT) B knockout mice, which suggests that abnormal urea metabolism may cause depression. The purpose of this study was to determine if urea accumulation in brain is a key factor causing depression using clinical data and animal models. Methods: A meta-analysis was used to identify the relationship between depression and chronic diseases. Functional Magnetic Resonance Imaging (fMRI) brain scans and common biochemical indexes were compared between the patients and healthy controls. We used behavioural tests, electrophysiology, and molecular profiling techniques to investigate the functional role and molecular basis in mouse models. Findings: After performing a meta-analysis, we targeted the relevance between chronic kidney disease (CKD) and depression. In a CKD mouse model and a patient cohort, depression was induced by impairing the medial prefrontal cortex. The enlarged cohort suggested that urea was responsible for depression. In mice, urea was sufficient to induce depression, interrupt long-term potentiation (LTP) and cause loss of synapses in several models. The mTORC1-S6K pathway inhibition was necessary for the effect of urea. Lastly, we identified that the hydrolysate of urea, cyanate, was also involved in this pathophysiology. Interpretation: These data indicate that urea accumulation in brain is an independent factor causing depression, bypassing the psychosocial stress. Urea or cyanate carbamylates mTOR to inhibit the mTORC1-S6K dependent dendritic protein synthesis, inducing impairment of synaptic plasticity in mPFC anddepression-like behaviour. CKD patients may be able to attenuate depression only by strict management of blood urea. (C) 2019 The Authors. Published by Elsevier B.V.

One influential theory on object knowledge is feature-based model, which proposes that the object knowledge is organized by different feature types, such as sensory/perceptual and motor/functional ones. Previous studies have shown that prior knowledge enhances the processes of acquiring and remembering relevant information. However, whether the effect of prior knowledge is applied to different types of conceptual information over time remains unclear. In this study, we addressed this question by testing memory of different types of object features at various retention intervals. The level of prior knowledge was manipulated as object features from familiar and unfamiliar categories. In Experiments 1 and 2, sentences that described the perceptual and functional features of new words were presented. Sentences with episodic features were additionally presented in Experiment 2. The participants were then tested with recognition (Experiment 1) and recall (Experiment 2) tasks at different retention intervals. The results showed that prior knowledge enhanced memory for perceptual features but not for functional and episodic features. Such enhancement depended on the recollection process. In addition, the effect of prior knowledge on perceptual features remained stable over time. This study clarified how different types of new factual information were acquired and maintained and highlighted the importance of prior knowledge in acquiring new conceptual knowledge with the passage of time.

BackgroundHuman autosomal dominant polycystic kidney disease (ADPKD) is characterized by bilateral renal cysts that lead to a decline in kidney function over time. Previous studies reported aquaporin‐3 (AQP3) expression in cysts derived from collecting ducts in ADPKD.MethodsTo study the contribution of AQP3 in cyst development, two PKD mouse models, kidney‐specific Pkd1 knockout mice and inducible Pkd1 knockout mice, were generated with or without AQP3 deletion. MDCK cell line was used to study the mechanism in which AQP3 affected cyst development.ResultsKidney size and cyst index were significantly smaller in AQP3‐null PKD mice than those in AQP3‐expressing PKD mice, with the difference due mainly to a smaller diameter of collecting duct cysts. AQP3 deficiency inhibits cystogenesis in inducible PKD mice. Importantly, AQP3 deficiency reduced the number of cysts from collecting duct (9.3±1.1 vs. 2.7±0.6) and their diameter. The diameter of AQP3‐MDCK cysts was significantly ~38% larger than in control MDCK cells. The percentage of AQP3‐MDCK cells that formed cysts was significantly lower than in control MDCK cells. AQP3 promoted cyst epithelia cells proliferation. Western‐blot analyses revealed that the expression levels of proliferating cell nuclear antigen (PCNA) in AQP3‐null PKD were reduced as compared with the PKD mice. Consistent with the results in vivo, intracellular ATP in AQP3 null kidney was 75% of that in AQP3‐expressing kidney. We found lower level of AMPK phosphorylation in AQP3‐MDCK cells as compared to MDCK cells. In vivo, the p‐AMPK in AQP3 null kidney was 2.4‐fold more than that in wild‐type kidney. The level of p‐AMPK in PKD mouse kidney was half of which in wild‐type control kidney. AQP3 gene deletion in PKD mice reversed the p‐AMPK level. AQP3 null kidney produced a significant increase in phosphorylated ACC (p‐ACC) levels. We found that S6 phosphorylation in AQP3‐MDCK cells was about 1.6 times as MDCK cells. Western blot revealed that p‐S6 in AQP3 null kidney was 17.7% of that in wild‐type kidney. The level of p‐S6 in PKD mouse kidney was 1.8 fold greater than that in wild‐type mouse kidney. AQP3 gene deletion in PKD mice reversed the p‐S6 to a normal level. The expression of GLUT1 was upregulated and expression of HIF1α was also increased in AQP3‐MDCK cells. These results suggest that AQP3 promotes glucose uptake by increasing GLUT1 expression. Indeed, glucose deprivation abrogated the decrease of p‐AMPK of AQP3‐MDCK cells.ConclusionThe experimental results indicate that AQP3 depletion retards cyst growth in part as a consequence of impaired AQP3‐dependent energy metabolism. These findings identify AQP3 as a potential target to reduce cyst development in ADPKD.Support or Funding InformationThis work was supported by National Natural Science Foundation of China grants 31200869, 81261160507, 81330074 and 81170632, and the 111 Project.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Aquaporin-3 (AQP3), a transporter of water, glycerol and H2O2, is expressed in basolateral membranes of principal cells in kidney collecting duct. Here, we report that AQP3 deletion in mice affects renal function and modulates renal injury. We found collecting duct hyperplasia and cell swelling in kidneys of adult AQP3 null mice. After mild renal ischemia-reperfusion (IR), AQP3 null mice had significantly greater blood urea nitrogen (57 mg/dl) and creatinine (136 μM) than wild-type mice (35 mg/dl and 48 μM, respectively), and showed renal morphological changes, including tubular dilatation, erythrocyte diapedesis and collecting duct incompletion. MPO, MDA and SOD following IR in AQP3 null mice were significantly different from that in wild-type mice (1.7 U/g vs 0.8 U/g, 3.9 μM/g vs 2.4 μM/g, 6.4 U/mg vs 11 U/mg, respectively). Following IR, AQP3 deletion inhibited activation of mitogen-activated protein kinase (MAPK) signaling and produced an increase in the ratios of Bax/Bcl-2, cleaved caspase-3/caspase-3 and p-p53/p53. Studies in transfected MDCK cells showed that AQP3 expression attenuated reduced cell viability following hypoxia-reoxygenation, with reduced apoptosis and increased MAPK signaling. Our results support a novel role for AQP3 in modulating renal injury and suggest the mechanisms involved in protection against hypoxic injury.

OBJECTIVE Human autosomal dominant polycystic kidney disease (ADPKD) is characterized by numerous bilateral renal cysts that lead to a decline in kidney function over time. Previous studies reported aquaporin‐3 (AQP3) expression in cysts derived from collecting ducts in ADPKD. The aim of this study is to study the effect of AQP3 on ADPKD development. METHODS AQP3 deficient PKD mice and inducible PKD mice were established in this study. Effect of AQP3 on PKD development was studied with pathological and molecular biological techniques. RESULTS In both models, kidney size and cyst number were ~30% smaller in AQP3 null PKD mice than in AQP3‐expressing PKD mice, with the difference due mainly to smaller collecting ducts cysts. In matrix cultured MDCK cyst model, AQP3 transfection promoted cyst enlargement. To investigate the mechanism of AQP3‐dependent cyst development, we detected related signaling pathways. It was found that the AMPK/ERK/mTOR signaling, as well as intracellular ATP, were down‐regulated after AQP3 deletion. In addition, overexpression of AQP3 increased intracellular ATP synthesis, and HIF1α and glucose transporter 1 expression. CONCLUSION We conclude that AQP3 depletion retards cyst growth, primarily due to AQP3‐dependent energy metabolism. These findings identified the AQP3 as a potential therapeutic target for treating ADPKD. Support or Funding Information This work was supported by National Natural Science Foundation of China grants 31200869, 81261160507, 81330074 and 81170632, and the 111 Project.

Autosomal dominant polycystic kidney disease (ADPKD) is a monogenetic disease that still lacks effective therapy. Repulsive guidance molecule b (RGMb), a co-receptor for bone morphogenetic proteins (BMPs) and a ligand for neogenin, is expressed in renal tubular epithelial cells. Previous studies showed that RGMb plays negative roles in several types of tumors and prevents the immune system from over activation. The present study was designed to explore the effects of RGMb in ADPKD development. We found that expression of RGMb in kidney was less in PKD mice than wild-type mice. With stimulation of 8-bromo-cAMP, RGMb-null embryonic kidneys had greater cyst index, though their ureteric bud branched less than wild-type mice at E13.5. Postnatal RGMb-null kidneys showed interstitial hyperplasia and decreased tubular structures, especially in the boundary area of renal cortex and medulla. RGMb overexpression dramatically inhibited cyst development and promoted tubulogenesis in MDCK cells grown in 3D collagen gels. Biochemical analysis showed increased p-Smad1/5/8 and decreased p-ERK in RGMb-overexpressing MDCK cells, suggesting modulated BMP signaling. Specific inhibition of p-Smad1/5/8 by LDN193189 reversed the suppression of RGMb on MDCK cyst model. These results reveal RGMb as a novel regulator for ADPKD by promoting renal tubule branching and regulating BMP signaling pathway. Elevating RGMb and enhancing p-Smad1/5/8 are promising new strategies to treat ADPKD.

Axonal tracing is useful for detecting optic nerve injury and regeneration, but many commonly used methods cannot be used to observe axoplasmic flow and synaptic transmission in vivo. Manganese (Mn2+)-enhanced magnetic resonance imaging (MEMRI) can be used for in vivo longitudinal tracing of the visual pathway. Here, we explored the dose response and time course of an intravitreal injection of MnCl2 for tracing the visual pathway in rabbits in vivo using MEMRI. We found that 2 mM MnCl2 enhanced images of the optic nerve but not the lateral geniculate body or superior colliculus, whereas at all other doses tested (5-40 mM), images of the visual pathway from the retina to the contralateral superior colliculus were significantly enhanced. The images were brightest at 24 hours, and then decreased in brightness until the end of the experiment (7 days). No signal enhancement was observed in the visual cortex at any concentration of MnCl2. These results suggest that MEMRI is a viable method for temporospatial tracing of the visual pathway in vivo. Signal enhancement in MEMRI depends on the dose of MnCl2, and the strongest signals appear 24 hours after intravitreal injection.

Urea transporters (UT) are a family of transmembrane urea-selective channel proteins expressed in multiple tissues and play an important role in the urine concentrating mechanism of the mammalian kidney. UT inhibitors have diuretic activity and could be developed as novel diuretics. To determine if functional deficiency of all UTs in all tissues causes physiological abnormality, we established a novel mouse model in which all UTs were knocked out by deleting an 87 kb of DNA fragment containing most parts of Slc14a1 and Slc14a2 genes. Western blot analysis and immunofluorescence confirmed that there is no expression of urea transporter in these all-UT-knockout mice. Daily urine output was nearly 3.5-fold higher, with significantly lower urine osmolality in all-UT-knockout mice than that in wild-type mice. All-UT-knockout mice were not able to increase urinary urea concentration and osmolality after water deprivation, acute urea loading, or high protein intake. A computational model that simulated UT-knockout mouse models identified the individual contribution of each UT in urine concentrating mechanism. Knocking out all UTs also decreased the blood pressure and promoted the maturation of the male reproductive system. Thus, functional deficiency of all UTs caused a urea-selective urine-concentrating defect with little physiological abnormality in extrarenal organs.

Mammalian urea transporters (UTs), UT-A and UT-B, are best known for their role in urine concentration. UT-B is especially distributed in multiple extrarenal tissues with abundant expression in vascular endothelium, but little is known about its role in vascular function. The present study investigated the physiological significance of UT-B in regulating vasorelaxations and blood pressure. UT-B deletion in mice or treatment with UT-B inhibitor PU-14 in Wistar-Kyoto rats (WKYs) and spontaneous hypertensive rats (SHRs) reduced blood pressure. Acetylcholine-induced vasorelaxation was significantly augmented in aortas from UT-B null mice. PU-14 concentration-dependently produced endothelium-dependent relaxations in thoracic aortas and mesenteric arteries from both mice and rats and the relaxations were abolished by N(ω)-nitro-L-arginine methyl ester. Both expression and phosphorylation of endothelial nitric oxide synthase (eNOS) were up-regulated and expression of arginase I was down-regulated when UT-B was inhibited both in vivo and in vitro. PU-14 induced endothelium-dependent relaxations to a similar degree in aortas from 12 weeks old SHRs or WKYs. In summary, here we report for the first time that inhibition of UT-B plays an important role in regulating vasorelaxations and blood pressure via up-regulation of L-arginine-eNOS-NO pathway, and it may become another potential therapeutic target for the treatment of hypertension.

Water channel aquaporin-1 (AQP1) is expressed at epithelial cell plasma membranes in renal proximal tubules and thin descending limb of Henle. Recently, AQP1 was reported to interact with β-catenin. Here we investigated the relationship between AQP1 and Wnt signaling in in vitro and in vivo models of autosomal dominant polycystic kidney disease (PKD). AQP1 overexpression decreased β-catenin and cyclinD1 expression, suggesting down-regulation of Wnt signaling, and coimmunoprecipitation showed AQP1 interaction with β-catenin, glycogen synthase kinase 3β, LRP6, and Axin1. AQP1 inhibited cyst development and promoted branching in matrix-grown MDCK cells. In embryonic kidney cultures, AQP1 deletion increased cyst development by up to ∼ 40%. Kidney size and cyst number were significantly greater in AQP1-null PKD mice than in AQP1-expressing PKD mice, with the difference mainly attributed to a greater number of proximal tubule cysts. Biochemical analysis revealed decreased β-catenin phosphorylation and increased β-catenin expression in AQP1-null PKD mice, suggesting enhanced Wnt signaling. These results implicate AQP1 as a novel determinant in renal cyst development that may involve inhibition of Wnt signaling by an AQP1-macromolecular signaling complex.

Background: The cAMP-PKA signaling pathway and TGF-β1-dependent fibrosis pathways are of particular importance in ADPKD progression, but the cross-talk between these pathways remains unclear. Therefore, we used an MDCK-cell model and embryonic kidney-cyst model to study the regulatory role of cAMP-PKA signaling in the TGF-β1 induced fibrotic process. Method and Results: Pkd1flox/flox; Ksp-Cre and Pkd1+/+; Ksp-Cre mice were used as an in vivo model. Increased kidney volume, renal cysts formation and up-regulation of the fibrosis-related proteins TGF-β1, connective tissue growth factor (CTGF), and fibronectin (FN) can be observed in Pkd1flox/flox; Ksp-Cre mice. In an embryonic kidneys-cyst model, TGF-β1, FN and collagen type I were highly expressed. Western blotting revealed the obviously up-regulation of TGF-β1, CTGF, FN and collagen type I expression following forskolin treatment in MDCK cells. Selective PKA inhibition with H89 may partially reversed the above effects. Pretreatment with the TGF-β RI kinase inhibitor VI SB431542 suppressed the increased expression of CTGF, FN and collagen type I caused by forskolin. Our data also indicate that forskolin inhibited TGF-β-induced ERK1/2 phosphorylation and FN up-regulation. ERK inhibition useing PD98059 significantly inhibited the expression of CTGF, FN and collagen type I caused by TGF-β1. Conclusions: The cAMP-PKA signaling pathway can directly promote the production of TGF-β1 and/or TGF-β1-dependent fibrogenetic molecules in MDCK cells and embryonic kidney cysts, but when TGF-β1 and its downstream pathways were highly expressed in MDCK cells, cAMP-PKA had a significantly negative effect on TGF-β1 induced p-ERK1/2 and FN expression.