Intrahippocampal Inoculation of Aß1-42 Peptide in Rat as a Model of Alzheimer's Disease Identified MicroRNA-146a-5p as Blood Marker with Anti-Inflammatory Function in Astrocyte Cells.

Circulating microRNAs (miRNAs) have aroused a lot of interest as reliable blood diagnostic biomarkers of Alzheimer's disease (AD). Here, we investigated the panel of expressed blood miRNAs in response to aggregated Aß1-42 peptides infused in the hippocampus of adult rats to mimic events of the early onset of non-familial AD disorder. Aß1-42 peptides in the hippocampus led to cognitive impairments associated with an astrogliosis and downregulation of circulating miRNA-146a-5p, -29a-3p, -29c-3p, -125b-5p, and-191-5p. We established the kinetics of expression of selected miRNAs and found differences with those detected in the APPswe/PS1dE9 transgenic mouse model. Of note, miRNA-146a-5p was exclusively dysregulated in the Aß-induced AD model. The treatment of primary astrocytes with Aß1-42 peptides led to miRNA-146a-5p upregulation though the activation of the NF-κB signaling pathway, which in turn downregulated IRAK-1 but not TRAF-6 expression. As a consequence, no induction of IL-1ß, IL-6, or TNF-α was detected. Astrocytes treated with a miRNA-146-5p inhibitor rescued IRAK-1 and changed TRAF-6 steady-state levels that correlated with the induction of IL-6, IL-1ß, and CXCL1 production, indicating that miRNA-146a-5p operates anti-inflammatory functions through a NF-κB pathway negative feedback loop. Overall, we report a panel of circulating miRNAs that correlated with Aß1-42 peptides' presence in the hippocampus and provide mechanistic insights into miRNA-146a-5p biological function in the development of the early stage of sporadic AD.

Pathological changes induced by Alzheimer's brain inoculation in amyloid-beta plaque-bearing mice.

Alzheimer's disease (AD) is characterized by intracerebral accumulations of extracellular amyloid-ß (Aß) plaques and intracellular tau pathology that spread in the brain. Three types of tau lesions occur in the form of neuropil threads, neurofibrillary tangles, and neuritic plaques i.e. tau aggregates within neurites surrounding Aß deposits. The cascade of events linking these lesions and synaptic or memory impairments are still debated. Intracerebral infusion of human AD brain extracts in Aß plaque-bearing mice that do not overexpress pathological tau proteins induces tau pathologies following heterotopic seeding of mouse tau protein. There is however little information regarding the downstream events including synaptic or cognitive repercussions of tau pathology induction in these models. In the present study, human AD brain extracts (ADbe) and control-brain extracts (Ctrlbe) were infused into the hippocampus of Aß plaque-bearing APPswe/PS1dE9 mice. Memory, synaptic density, as well as Aß plaque and tau aggregate loads, microgliosis, astrogliosis at the inoculation site and in connected regions (perirhinal/entorhinal cortex) were evaluated 4 and 8 months post-inoculation. ADbe inoculation produced the following effects: (i) memory deficit; (ii) increased Aß plaque deposition in proximity to the inoculation site; (iii) tau pathology induction; (iv) appearance of neuropil threads and neurofibrillary tangles next to the inoculation site with a spreading to connected regions. Neuritic plaque pathology was detected in both ADbe- and Ctrlbe-inoculated animals but ADbe inoculation increased the severity close to and at distance of the inoculation site. (v) Finally, ADbe inoculation reduced synaptic density in the vicinity to the inoculation site and in connected regions as the perirhinal/entorhinal cortex. Synaptic impairments were correlated with increased severity of neuritic plaques but not to other tau lesions or Aß lesions, suggesting that neuritic plaques are a culprit for synaptic loss. Synaptic density was also associated with microglial load.

Transmission of amyloid-beta and tau pathologies is associated with cognitive impairments in a primate.

Amyloid-ß (Aß) pathology transmission has been described in patients following iatrogenic exposure to compounds contaminated with Aß proteins. It can induce cerebral Aß angiopathy resulting in brain hemorrhages and devastating clinical impacts. Iatrogenic transmission of tau pathology is also suspected but not experimentally proven. In both scenarios, lesions were detected several decades after the putatively triggering medico-surgical act. There is however little information regarding the cognitive repercussions in individuals who do not develop cerebral hemorrhages. In the current study, we inoculated the posterior cingulate cortex and underlying corpus callosum of young adult primates (Microcebus murinus) with either Alzheimer's disease or control brain extracts. This led to widespread Aß and tau pathologies in all of the Alzheimer-inoculated animals following a 21-month-long incubation period (n = 12) whereas none of the control brain extract-inoculated animals developed such lesions (n = 6). Aß deposition affected almost all cortical regions. Tau pathology was also detected in Aß-deposit-free regions distant from the inoculation sites (e.g. in the entorhinal cortex), while some regions adjacent, but not connected, to the inoculation sites were spared (e.g. the occipital cortex). Alzheimer-inoculated animals developed cognitive deficits and cerebral atrophy compared to controls. These pathologies were induced using two different batches of Alzheimer brain extracts. This is the first experimental demonstration that tau can be transmitted by human brain extracts inoculations in a primate. We also showed for the first time that the transmission of widespread Aß and tau pathologies can be associated with cognitive decline. Our results thus reinforce the need to organize a systematic monitoring of individuals who underwent procedures associated with a risk of Aß and tau iatrogenic transmission. They also provide support for Alzheimer brain-inoculated primates as relevant models of Alzheimer pathology.

Induction of amyloid-ß deposits from serially transmitted, histologically silent, Aß seeds issued from human brains.

In humans, iatrogenic transmission of cerebral amyloid-ß (Aß)-amyloidosis is suspected following inoculation of pituitary-derived hormones or dural grafts presumably contaminated with Aß proteins as well as after cerebral surgeries. Experimentally, intracerebral inoculation of brain homogenate extracts containing misfolded Aß can seed Aß deposition in transgenic mouse models of amyloidosis or in non-human primates. The transmission of cerebral Aß is governed by the host and by the inoculated samples. It is critical to better characterize the propensities of different hosts to develop Aß deposition after contamination by an Aß-positive sample as well as to better assess which biological samples can transmit this lesion. Aß precursor protein (huAPPwt) mice express humanized non-mutated forms of Aß precursor protein and do not spontaneously develop Aß or amyloid deposits. We found that inoculation of Aß-positive brain extracts from Alzheimer patients in these mice leads to a sparse Aß deposition close to the alveus 18 months post-inoculation. However, it does not induce cortical or hippocampal Aß deposition. Secondary inoculation of apparently amyloid deposit-free hippocampal extracts from these huAPPwt mice to APPswe/PS1dE9 mouse models of amyloidosis enhanced Aß deposition in the alveus 9 months post-inoculation. This suggests that Aß seeds issued from human brain samples can persist in furtive forms in brain tissues while maintaining their ability to foster Aß deposition in receptive hosts that overexpress endogenous Aß. This work emphasizes the need for high-level preventive measures, especially in the context of neurosurgery, to prevent the risk of iatrogenic transmission of Aß lesions from samples with sparse amyloid markers.

Encephalopathy induced by Alzheimer brain inoculation in a non-human primate.

Alzheimer's disease is characterized by cognitive alterations, cerebral atrophy and neuropathological lesions including neuronal loss, accumulation of misfolded and aggregated ß-amyloid peptides (Aß) and tau proteins. Iatrogenic induction of Aß is suspected in patients exposed to pituitary-derived hormones, dural grafts, or surgical instruments, presumably contaminated with Aß. Induction of Aß and tau lesions has been demonstrated in transgenic mice after contamination with Alzheimer's disease brain homogenates, with very limited functional consequences. Unlike rodents, primates naturally express Aß or tau under normal conditions and attempts to transmit Alzheimer pathology to primates have been made for decades. However, none of earlier studies performed any detailed functional assessments. For the first time we demonstrate long term memory and learning impairments in a non-human primate (Microcebus murinus) following intracerebral injections with Alzheimer human brain extracts. Animals inoculated with Alzheimer brain homogenates displayed progressive cognitive impairments (clinical tests assessing cognitive and motor functions), modifications of neuronal activity (detected by electroencephalography), widespread and progressive cerebral atrophy (in vivo MRI assessing cerebral volume loss using automated voxel-based analysis), neuronal loss in the hippocampus and entorhinal cortex (post mortem stereology). They displayed parenchymal and vascular Aß depositions and tau lesions for some of them, in regions close to the inoculation sites. Although these lesions were sparse, they were never detected in control animals. Tau-positive animals had the lowest performances in a memory task and displayed the greatest neuronal loss. Our study is timely and important as it is the first one to highlight neuronal and clinical dysfunction following inoculation of Alzheimer's disease brain homogenates in a primate. Clinical signs in a chronic disease such as Alzheimer take a long time to be detectable. Documentation of clinical deterioration and/or dysfunction following intracerebral inoculations with Alzheimer human brain extracts could lead to important new insights about Alzheimer initiation processes.

Does Rheumatoid Arthritis Really Improve During Pregnancy? A Systematic Review and Metaanalysis.

OBJECTIVE: We performed a systematic review and metaanalysis to assess rheumatoid arthritis (RA) disease activity during pregnancy using objective disease activity scoring systems. METHODS: A systematic review of PubMed, EMBASE/Medline, Cochrane, and LactMed databases was performed. Our inclusion criteria for analysis were prospective studies, more than 5 patients per study, and data on RA using an objective scoring system conducted by a clinician/health professional. RESULTS: Ten studies were eligible for final analysis, which included 237 patients, of which prepartum data were available for 204 patients. Postpartum disease activity was recorded in 135 pregnancies. CONCLUSION: Disease activity improved in 60% of patients with RA in pregnancy and flared in 46.7% postpartum.

Interaction between p53 mutation and a somatic HDMX biomarker better defines metastatic potential in breast cancer.

TP53 gene mutation is associated with poor prognosis in breast cancer, but additional biomarkers that can further refine the impact of the p53 pathway are needed to achieve clinical utility. In this study, we evaluated a role for the HDMX-S/FL ratio as one such biomarker, based on its association with other suppressor mutations that confer worse prognosis in sarcomas, another type of cancer that is surveilled by p53. We found that HDMX-S/FL ratio interacted with p53 mutational status to significantly improve prognostic capability in patients with breast cancer. This biomarker pair offered prognostic utility that was comparable with a microarray-based prognostic assay. Unexpectedly, the utility tracked independently of DNA-damaging treatments and instead with different tumor metastasis potential. Finally, we obtained evidence that this biomarker pair might identify patients who could benefit from anti-HDM2 strategies to impede metastatic progression. Taken together, our work offers a p53 pathway marker, which both refines our understanding of the impact of p53 activity on prognosis and harbors potential utility as a clinical tool.

Wild-type p53 inhibits pro-invasive properties of TGF-ß3 in breast cancer, in part through regulation of EPHB2, a new TGF-ß target gene.

The p53 tumor suppressor protein is primarily known for its important role in tumor suppression. In addition, p53 affects tumor cell migration, invasion, and epithelial-mesenchymal transition (EMT); processes also regulated by the transforming growth factor-ß (TGF-ß) signaling pathway. Here, we investigated the role of p53 in breast tumor cell invasion, migration, and EMT and examined the interplay of p53 with TGF-ß3 in these processes. MCF-10A1 and MCF-10CA1a breast cancer cells were treated with Nutlin-3 and TGF-ß3, and the effects on tumor cell migration and invasion were studied in transwell and 3D spheroid invasion assays. The effects of Nutlin-3 and TGF-ß3 on EMT were examined in NMuMG cells. To identify genes involved in TGF-ß-induced invasion that are modulated by p53, a Human Tumor Metastasis-specific RT-PCR array was performed. Verification of EPHB2 regulation by TGF-ß3 and p53 was performed on breast cancer tumor cell lines. We demonstrate that p53 inhibits basal and TGF-ß3-induced invasion, migration, and EMT in normal breast epithelial and breast cancer cells. Pharmacological activation of p53 inhibited induction of several TGF-ß3 targets involved in TGF-ß3-induced tumor cell invasion, i.e., matrix metallo proteinase (MMP)2, MMP9, and integrin ß 3 . The ephrin-type B receptor 2 (EPHB2) gene was identified as a new TGF-ß target important for TGF-ß3-mediated invasion and migration, whose transcriptional activation by TGF-ß3 is also inhibited by p53. The results show an intricate interplay between p53 and TGF-ß3 whereby p53 inhibits the TGF-ß3-induced expression of genes, e.g., EPHB2, to impede tumor cell invasion and migration.

High levels of Hdmx promote cell growth in a subset of uveal melanomas.

The p53 tumor suppressor pathway is inactivated in cancer either via direct mutation or via deregulation of upstream regulators or downstream effectors. P53 mutations are rare in uveal melanoma. Here we investigated the role of the p53 inhibitor Hdmx in uveal melanoma. We found Hdmx over-expression in a subset of uveal melanoma cell lines and fresh-frozen tumor samples. Hdmx depletion resulted in cell-line dependent growth inhibition, apparently correlating with differential Hdm2 levels. Surprisingly, p53 knockdown hardly rescued cell cycle arrest and apoptosis induction upon Hdmx knockdown, whereas it effectively prevented growth suppression induced by the potent p53 activator Nutlin-3. In addition, two compounds inhibiting Hdmx function or expression, SAH-p53-8 and XI-011, also elicited a growth inhibitory effect in a partly p53-independent manner. These findings suggest a novel, growth-promoting function of Hdmx that does not rely on its ability to inhibit p53. We provide evidence for a contribution of p27 protein induction to the observed p53-independent G1 arrest in response to Hdmx knockdown. In conclusion, our study establishes the importance of Hdmx as an oncogene in a subset of uveal melanomas and widens the spectrum of its function beyond p53 inhibition.

HDMX-L is expressed from a functional p53-responsive promoter in the first intron of the HDMX gene and participates in an autoregulatory feedback loop to control p53 activity.

The p53 regulatory network is critically involved in preventing the initiation of cancer. In unstressed cells, p53 is maintained at low levels and is largely inactive, mainly through the action of its two essential negative regulators, HDM2 and HDMX. p53 abundance and activity are up-regulated in response to various stresses, including DNA damage and oncogene activation. Active p53 initiates transcriptional and transcription-independent programs that result in cell cycle arrest, cellular senescence, or apoptosis. p53 also activates transcription of HDM2, which initially leads to the degradation of HDMX, creating a positive feedback loop to obtain maximal activation of p53. Subsequently, when stress-induced post-translational modifications start to decline, HDM2 becomes effective in targeting p53 for degradation, thus attenuating the p53 response. To date, no clear function for HDMX in this critical attenuation phase has been demonstrated experimentally. Like HDM2, the HDMX gene contains a promoter (P2) in its first intron that is potentially inducible by p53. We show that p53 activation in response to a plethora of p53-activating agents induces the transcription of a novel HDMX mRNA transcript from the HDMX-P2 promoter. This mRNA is more efficiently translated than that expressed from the constitutive HDMX-P1 promoter, and it encodes a long form of HDMX protein, HDMX-L. Importantly, we demonstrate that HDMX-L cooperates with HDM2 to promote the ubiquitination of p53 and that p53-induced HDMX transcription from the P2 promoter can play a key role in the attenuation phase of the p53 response, to effectively diminish p53 abundance as cells recover from stress.

Papillary renal cell carcinoma with diffuse clear cells and thyroid-like macrofollicular areas.

Papillary renal cell carcinoma may display some unusual morphologic variations, including diffuse oncocytic change not otherwise specified, oncocytic change associated with an inverted nuclear pattern or nonoverlapping low-grade nuclei, low-grade spindle cells, and diffuse clear cells. Tumors comprised predominantly of thyroid-like follicles and inspissated eosoinophilic, colloid-like secretions (thyroid-like follicular carcinoma of the kidney) have been recently recognized. We report herein an unusual renal carcinoma that displayed diffuse clear cells, papillary architecture, foamy histiocytes, psammomatous calcifications, and large areas (approximately 20% of tumor volume) with thyroid macrofollicular-like structures and eosinophilic, colloid-like secretions. The tumor was diffusely positive for alpha-methylacyl-CoA racemase, cytokeratin 7 and CD10, and was entirely negative for CD15, thyroglobulin, thyroid-transcription factor-1, TFE3, and renal cell carcinoma antigen. Fluorescence in situ hybridization using centromeric DNA probes for chromosomes 7, 17, 3, and 3p25 showed gains only in chromosome 7 and no other aberrations. The tumor was accordingly classified as an unusual morphologic variation of papillary renal cell carcinoma. This case affirms the potential for papillary renal cell carcinoma to display a diffuse complement of clear cells, and documents the heretofore unreported finding of large areas of thyroid macrofollicular structures and eosinophilic, colloid-like secretions in this histotype.

Distinct gene mutation profiles among luminal-type and basal-type breast cancer cell lines.

Breast cancer has for long been recognized as a highly diverse tumor group, but the underlying genetic basis has been elusive. Here, we report an extensive molecular characterization of a collection of 41 human breast cancer cell lines. Protein and gene expression analyses indicated that the collection of breast cancer cell lines has retained most, if not all, molecular characteristics that are typical for clinical breast cancers. Gene mutation analyses identified 146 oncogenic mutations among 27 well-known cancer genes, amounting to an average of 3.6 mutations per cell line. Mutations in genes from the p53, RB and PI3K tumor suppressor pathways were widespread among all breast cancer cell lines. Most important, we have identified two gene mutation profiles that are specifically associated with luminal-type and basal-type breast cancer cell lines. The luminal mutation profile involved E-cadherin and MAP2K4 gene mutations and amplifications of Cyclin D1, ERBB2 and HDM2, whereas the basal mutation profile involved BRCA1, RB1, RAS and BRAF gene mutations and deletions of p16 and p14ARF. These subtype-specific gene mutation profiles constitute a genetic basis for the heterogeneity observed among human breast cancers, providing clues for their underlying biology and providing guidance for targeted pharmacogenetic intervention in breast cancer patients.

Central chondrosarcoma progression is associated with pRb pathway alterations: CDK4 down-regulation and p16 overexpression inhibit cell growth in vitro.

Chondrosarcomas are highly resistant to conventional radiation and chemotherapy, and surgical removal is the only option for curative treatment. Consequently, there is nothing to offer patients with inoperable tumours and metastatic disease. The aim of this study is to investigate genes involved in cell cycle control: CDK4, CDKN2A/p16, cyclin D1, p21, p53, MDM2 and c-MYC, which may point towards new therapeutic strategies. The pRb pathway was targeted using CDKN2A/p16 overexpressing vectors and shRNA against CDK4 in chondrosarcoma cell lines OUMS27, SW1353, and CH2879. Cell survival and proliferation were assessed. CDK4, MDM2 and c-MYC expression levels were investigated by qPCR and immunohistochemistry (IHC) in 34 fresh frozen and 90 FFPE samples of enchondroma and chondrosarcoma patients. On a subset of 29 high-grade chondrosarcomas IHC for cyclin D1, p21 and p53 was performed. The overexpression of CDKN2A/p16 and knockdown of CDK4 by shRNA in OUMS27, SW1353 and CH2879 resulted in a significant decrease in cell viability and proliferation and a decreased ability to form colonies in vitro. Expression of CDK4 and MDM2 was associated with high-grade chondrosarcoma both at the mRNA and protein level. Combining these results with the expression of cyclin D1 and the previously shown loss of CDKN2A/p16 expression show that the majority (96%; 28/29) of high-grade chondrosarcomas contain alterations in the pRb pathway. This suggests a role for the use of CDK4 inhibitors as a treatment of metastatic or inoperable high-grade chondrosarcoma.

Inactivation of the p53 pathway in retinoblastoma.

Most human tumours have genetic mutations in their Rb and p53 pathways, but retinoblastoma is thought to be an exception. Studies suggest that retinoblastomas, which initiate with mutations in the gene retinoblastoma 1 (RB1), bypass the p53 pathway because they arise from intrinsically death-resistant cells during retinal development. In contrast to this prevailing theory, here we show that the tumour surveillance pathway mediated by Arf, MDM2, MDMX and p53 is activated after loss of RB1 during retinogenesis. RB1-deficient retinoblasts undergo p53-mediated apoptosis and exit the cell cycle. Subsequently, amplification of the MDMX gene and increased expression of MDMX protein are strongly selected for during tumour progression as a mechanism to suppress the p53 response in RB1-deficient retinal cells. Our data provide evidence that the p53 pathway is inactivated in retinoblastoma and that this cancer does not originate from intrinsically death-resistant cells as previously thought. In addition, they support the idea that MDMX is a specific chemotherapeutic target for treating retinoblastoma.

Differential roles of ATM- and Chk2-mediated phosphorylations of Hdmx in response to DNA damage.

The p53 tumor suppressor plays a major role in maintaining genomic stability. Its activation and stabilization in response to double strand breaks (DSBs) in DNA are regulated primarily by the ATM protein kinase. ATM mediates several posttranslational modifications on p53 itself, as well as phosphorylation of p53's essential inhibitors, Hdm2 and Hdmx. Recently we showed that ATM- and Hdm2-dependent ubiquitination and subsequent degradation of Hdmx following DSB induction are mediated by phosphorylation of Hdmx on S403, S367, and S342, with S403 being targeted directly by ATM. Here we show that S367 phosphorylation is mediated by the Chk2 protein kinase, a downstream kinase of ATM. This phosphorylation, which is important for subsequent Hdmx ubiquitination and degradation, creates a binding site for 14-3-3 proteins which controls nuclear accumulation of Hdmx following DSBs. Phosphorylation of S342 also contributed to optimal 14-3-3 interaction and nuclear accumulation of Hdmx, but phosphorylation of S403 did not. Our data indicate that binding of a 14-3-3 dimer and subsequent nuclear accumulation are essential steps toward degradation of p53's inhibitor, Hdmx, in response to DNA damage. These results demonstrate a sophisticated control by ATM of a target protein, Hdmx, which itself is one of several ATM targets in the ATM-p53 axis of the DNA damage response.

Cross-linking tumor cells with effector cells via CD55 with a bispecific mAb induces beta-glucan-dependent CR3-dependent cellular cytotoxicity.

Complement (C) regulatory proteins decrease the effectiveness of immunotherapeutic anti-cancer antibodies. Bispecific mAb (bi-mAb) that target a tumor antigen and simultaneously inhibit a C regulator increase the effectiveness of such a therapy. Here we investigated the mechanism by which bi-mAb increase tumor cell lysis. Apart from C-dependent cytotoxicity, C activation can lead to complement receptor 3 (CR3)-dependent cellular cytotoxicity (CR3-DCC) by CR3-positive effector cells in the presence of beta-glucan. Here we show that an anti-Ep-CAM*anti-CD55 bi-mAb induced more than threefold higher CR3-DCC (71%) of human colorectal cancer cells compared with anti-Ep-CAM alone (20%). This CR3-DCC was dependent on the binding of the anti-CD55 arm of tumor-bound anti-Ep-CAM*anti-CD55 bi-mAb to effector cell CD55, CR3 priming by beta-glucan and the presence of iC3b on the target cell. Comparable lysis could be obtained in the absence of iC3b, when CR3 and CD55 were cross-linked on the effector cells, suggesting cooperation between CD55 and CR3 in signal transduction. Tumor cells with low antigen expression were effectively lysed via this mechanism in contrast to direct C-dependent cytotoxicity. These data imply that the effectiveness of mAb immunotherapy can be improved using anti-tumor antigen*anti-CD55 bi-mAb and beta-glucan, thereby initiating CR3-DCC as an additional effector mechanism that is efficient for eradication of tumor cells with lower antigen expression.

Inhibiting complement regulators in cancer immunotherapy with bispecific mAbs.

Although monoclonal antibody (mAb)-mediated immunotherapy of cancer has been proven to be feasible for clinical use, success rates until now have been disappointing. One reason for this might be the overexpression of membrane-bound complement regulatory proteins (mCRPs) by tumour cells. As complement activation is an important effector mechanism induced by therapeutic mAbs, inhibition of complement activation by tumour cells might reduce therapeutic efficacy by decreasing direct complement-mediated lysis as well as complement-dependent cellular cytotoxicity. Modulation of the function of these mCRPs might be achieved with therapeutic bispecific (bi-)mAbs that target a tumour antigen and simultaneously block a major mCRP. Clinical results will probably increase with such bi-mAbs compared with monovalent antitumour mAbs. In this review the feasibility of this approach is discussed.

Secretion of collagen type IV by human renal fibroblasts is increased by high glucose via a TGF-beta-independent pathway.

BACKGROUND: Tubulointerstitial fibrosis is an important component of diabetic nephropathy, which is characterized by increased expression of interstitial extracellular matrix components and aberrant expression of the basement membrane component collagen type IV. The present study examined the effect of high ambient glucose and transforming growth factor-beta1 (TGF-beta1) on collagen secretion by human renal fibroblasts and proximal tubular epithelial cells (PTECs). METHODS: Human renal fibroblasts (TK173) and PTECs (HK2) were used to examine the effects of high glucose (25 mM d-glucose) and TGF-beta1 (1 ng/ml) on collagen type I, III and IV secretion compared with control medium (5.5 mM glucose). Matrix components were measured by enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Renal fibroblasts are the main producers of the interstitial components collagen type I and type III, while collagen type IV was secreted predominantly by PTECs. However, renal fibroblasts were also able to secrete collagen type IV. Secretion of collagen type IV by fibroblasts was increased upon stimulation with TGF-beta1, reaching levels comparable with those secreted by TGF-beta1-induced PTECs. Moreover, high glucose stimulated increased collagen type IV secretion. Importantly, this could not be attenuated by neutralizing pan-specific anti-TGF-beta antibodies. CONCLUSIONS: These data show that renal fibroblasts secrete collagen type IV, which can be increased by high glucose independent of endogenous TGF-beta. This suggests that as well as the increased expression of interstitial components, renal fibroblasts can contribute to the increased expression of the basement membrane component collagen type IV in tubulointerstitial fibrosis observed during diabetic nephropathy.

Connective tissue growth factor and igf-I are produced by human renal fibroblasts and cooperate in the induction of collagen production by high glucose.

Tubulointerstitial fibrosis is an important component in the development of diabetic nephropathy. Various renal cell types, including fibroblasts, contribute to the excessive matrix deposition in the kidney. Although transforming growth factor-beta (TGF-beta) has been thought to play a major role during fibrosis, other growth factors are also involved. Here we examined the effects of connective tissue growth factor (CTGF) and IGF-I on collagen type I and III production by human renal fibroblasts and their involvement in glucose-induced matrix accumulation. We have demonstrated that both CTGF and IGF-I expressions were increased in renal fibroblasts under hyperglycemic conditions, also in the absence of TGF-beta signaling. Although CTGF alone had no effect on collagen secretion, combined stimulation with IGF-I enhanced collagen accumulation. Furthermore, IGF-I also had a synergistic effect with glucose on the induction of collagens. Moreover, we observed a partial inhibition in glucose-induced collagen secretion with neutralizing anti-CTGF antibodies, thereby demonstrating for the first time the involvement of endogenous CTGF in glucose-induced effects in human renal fibroblasts. Therefore, the cooperation between CTGF and IGF-I might be involved in glucose-induced matrix accumulation in tubulointerstitial fibrosis and might contribute to the pathogenesis of diabetic nephropathy.

Glucose-induced fibronectin and collagen type III expression in renal fibroblasts can occur independent of TGF-beta1.

BACKGROUND: Various renal cell types have been shown to contribute to the excessive matrix deposition observed in diabetic nephropathy. The present study examined the effect of high ambient glucose and transforming growth factor-beta1 (TGF-beta1) on matrix production by human renal fibroblasts. METHODS: Human renal fibroblasts (TK173) were used to examine the effects of high glucose and TGF-beta1 on fibronectin and collagen type III expression. Stable transfectants were generated of TK173 cells expressing a dominant negative TGF-beta type II receptor. Matrix components were measured in enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Fibronectin secretion by renal fibroblasts was increased upon exposure to high glucose, but with delayed kinetics compared to TGF-beta1-induced fibronectin. Exposure to high glucose resulted in an increased secretion of latent TGF-beta1. However, treatment with neutralizing pan-specific anti-TGF-beta antibodies could not attenuate the effects of glucose. Furthermore, collagen type III was up-regulated by high glucose, but not by TGF-beta1. Importantly, fibroblasts expressing a dominant negative TGF-beta type II receptor were defective in TGF-beta1-induced fibronectin production, whereas glucose-induced fibronectin and collagen type III were unaffected. CONCLUSIONS: These data show that in renal fibroblasts exposure to high glucose can increase matrix production independent of endogenous TGF-beta1. Although glucose activation is accompanied by an increased production of latent TGF-beta1, which can have an important role in vivo, the data suggest involvement of alternative growth factors in the mechanism by which hyperglycemic conditions can modulate matrix accumulation in diabetic nephropathy.