Background— Severe obesity can result in proteinuria and progressive glomerulosclerosis in humans and experimental animals. The associated renal disease is ameliorated by weight reduction and/or blockade of the renin-angiotensin system. Various growth factors, cytokines, and lipid mediators are implicated in the pathogenesis of renal disease. To explore the possible involvement of these mediators in obesity-induced renal disease, we examined the expression of key enzymes of arachidonate metabolism and inflammatory genes in untreated and losartan-treated obese Zucker rats, a model of obesity, insulin resistance, and renal injury. Methods and Results— Seven-week-old male obese Zucker rats were randomized to losartan-treated (100 mg/L drinking H 2 O) and untreated groups, with lean Zucker rats as controls. After 4 months, RNA and protein were obtained from renal cortical tissue for relative reverse transcription–polymerase chain reaction, Western blots, and immunohistochemistry. Compared with the lean controls, obese Zucker rats showed significant glomerular matrix expansion and increased mRNA expression of the extracellular matrix protein fibronectin, inflammatory mediators interleukin-6 and monocyte chemoattractant protein-1, and 2 major enzymes of arachidonate metabolism, namely, 12/15-lipoxygenase and cyclooxygenase-2. This was associated with significant increases in p38 and extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinase activities and marked upregulation of angiotensin II type 1 receptor (AT1R) mRNA and protein expression. These abnormalities and the associated glomerulopathy and proteinuria were prevented by administration of the AT1R blocker losartan. Conclusions— These findings indicate that obesity-induced glomerulopathy is associated with upregulation of key inflammatory mediators. These events are associated with and perhaps in part due to upregulation of AT1R, as evidenced by their reversal with AT1R blocker treatment.
Diabetic nephropathy (DN) is characterized by mesangial cell (MC) expansion and accumulation of extracellular matrix proteins. TGF-beta is increased in MC under diabetic conditions and in DN and activates key signaling pathways, including the phosphoinositide-3-kinase/Akt (PI3K/Akt) pathway. FoxO transcription factors play roles in cell survival and oxidative stress and are negatively regulated by Akt-mediated phosphorylation. We tested whether phosphorylation-mediated inactivation of FoxO3a by TGF-beta can mediate MC survival and oxidative stress. TGF-beta treatment significantly increased levels of p-Akt (activation) and p-FoxO3a (inactivation) in cultured MC. This FoxO3a inactivation was accompanied by significant decreases in the expression of two key FoxO3a target genes, the proapoptotic Bim and antioxidant manganese superoxide dismutase in MC. TGF-beta treatment triggered the nuclear exclusion of FoxO3a, significantly inhibited FoxO3a transcriptional activity, and markedly protected MC from apoptosis. A PI3K inhibitor blocked these TGF-beta effects. It is interesting that p-Akt and p-FoxO3A levels also were increased in renal cortical tissues from rats and mice at 2 wk after the induction of diabetes by streptozotocin, thus demonstrating in vivo significance. In summary, TGF-beta and diabetes can increase FoxO3a phosphorylation and transcriptional inactivation via PI3K/Akt. These new results suggest that Akt/FoxO pathway regulation may be a novel mechanism by which TGF-beta can induce unopposed MC survival and oxidant stress in early DN, thereby accelerating renal disease.
Diabetic nephropathy (DN) remains a major complication in both type 1 and type 2 diabetes. Systemic administration of antitransforming growth factor-beta (TGF-beta) antibody has shown some promise in mouse models of DN. However, chronic blockade of the multifunctional TGB-beta could be problematic. Several downstream effects of TGF-beta are mediated by connective tissue growth factor (CTGF), which is up-regulated in several renal cells and secreted in the urine in the diabetic state. Using murine models of DN (type 1 and type 2) and a CTGF antisense oligonucleotide (ASO) of novel chimeric chemistry, we evaluated the specific role of this target in DN. In the type 1 model of DN, C57BL6 mice were made diabetic using streptozotocin injections and hyperglycemic animals were treated with CTGF ASOs (20 mg/kg/2 qw) for 4 months. ASO, but not mismatch control oligonucleotide, -treated animals showed significant reduction in target CTGF expression in the kidney with a concomitant decrease in proteinuria and albuminuria. Treatment with the CTGF ASO for 8 wk reduced serum creatinine and attenuated urinary albuminuria and proteinuria in diabetic db/db mice, a model of type 2 DN. The ASO also reduced expression of genes involved in matrix expansion such as fibronectin and collagen (I and IV) and an inhibitor of matrix degradation, PAI-1, in the renal cortex, contributing to significant reversal of mesangial expansion in both models of DN. Pathway analyses demonstrated that diabetes-induced phosphorylation of p38 MAPK and its downstream target CREB was also inhibited by the ASO. Our results strongly suggest that blocking CTGF using a chimeric ASO holds substantial promise for the treatment of DN.
Immunoglobulin light chain amyloidosis is a clonal, non-proliferative plasma cell disorder, in which fragments of immunoglobulin light chain are deposited in tissues. Clinical features depend on organs involved but can include restrictive cardiomyopathy, nephrotic syndrome, hepatic failure, peripheral/autonomic neuropathy, and atypical multiple myeloma. Membranous nephropathy (MN) is a group of diseases characterized by deposition of immune complexes under the epithelial cells of glomerular basement and diffuse thickening of the basement membrane. Most patients with idiopathic MN (IMN) have been exposed to phospholipase A2 receptor (PLA2R) antigen, and anti-PLA2R antibodies that attack podocytes can be detected in their blood. IMN combined with amyloidosis nephropathy without secondary factors is rare. The present study describes a patient with IMN combined with immunoglobulin light chain amyloidosis nephropathy.A 39-year-old man was admitted to our hospital because of weight loss and edema. His clinical manifestation was nephrotic syndrome. Renal pathology revealed MN. A positive Congo red staining and the pathognomonic apple-green birefringence under cross-polarized light were considered to be associated with amyloid nephropathy. Immunofluorescence showed that λ light chain was positive. Heavy chain deposition disease and amyloid-associated protein amyloidosis were excluded by immunofluorescence and immunohistochemistry, respectively. Subsequent examinations showed that his serum was negative for antibodies against the PLA2R, but PLA2R was present in renal tissue. The final diagnosis was IMN with light chain amyloid nephropathy.Renal amyloidosis accompanied by IMN is uncommon. Attention should be paid to the subtype of the disease and the exclusion of secondary factors. Perfect clinical and pathological examination are helpful for the classification and staging of the disease. Congo red staining, light microscopy, immunofluorescence, immunohistochemistry, electron microscopic examination, pathological tissue staining for PLA2R antigen and testing for anti-PLA2R antibody in serum are helpful.
Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and membranous nephropathy (MN) are two types of diseases that can both involve kidneys.In recent years, there are some reports about the concurrence of these two diseases.However, the precise mechanism, clinical course, and optimal treatment of patients with this unusual combination of renal diseases are little known.Previously reported cases of MN combined with AAV presented characteristics of both MN and crescentic glomerulonephritis, manifesting rapid disease progression and poor prognosis.Diagnosis and treatment are essential and challenging.Here, we report a case of AAV and MN in a 62 years old man, who was admitted to hospital due to edema, low-grade fever, and cough.The patient showed a different pathological feature from previous cases, with no crescent formation.By analyzing the diagnoses and potential pathogenesis, we considered MN was secondary to the present AAV and suspected the existence of other alternative mechanisms.Also, we applied a new therapy, glucocorticoid with mizoribine.After one-year follow-up, this treatment is feasible, safe, and leads to a clinical improvement for AAV combined with MN.In this case, two diseases overlapped, and the laboratory analysis and pathology are both required to ensure diagnostic accuracy.The principal aim of this case report is to highlight the diagnostic challenge and distinct treatment in the simultaneous occurrence of AAV combined with MN.
<b><i>Background/Aims:</i></b> Arachidonic acid-metabolizing enzyme, 12-lipoxygenase (12-LO), is involved in the glomerular hypertrophy of diabetic nephropathy (DN), in which cyclin-dependent kinase inhibitors (CKIs) play important roles. However, it is unclear whether 12-LO regulates the expression of the CKI p16<sup>ink4a</sup> in DN. <b><i>Methods:</i></b> Primary glomerular mesangial cells (MCs) and glomeruli isolated from rats were used in this study. The rats were fed a high-fat diet and given low-dose streptozotocin to induce type 2 diabetes. The 12-LO product, 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), was infused through an osmotic minipump. Enzyme-linked immunosorbent assay, Western blot, and morphometric analyses were performed. <b><i>Results:</i></b> High glucose (HG) increased the p16<sup>ink4a</sup> protein expression in MCs, but this increase was prevented by the 12-LO inhibitor, cinnamyl-3,​4-dihydroxy-α-cynanocinnamate (CDC). The levels of p-p38MAPK and p16<sup>ink4a</sup> in MCs were significantly elevated after the 12(S)-HETE treatment, whereas the p38MAPK inhibitor SB203580 prevented these increases. Compared with levels in control MCs, marked increases in p38MAPK activation and p16<sup>ink4a</sup> expression were observed in MCs plated on collagen IV, while the CDC treatment prevented these changes. Subcutaneous injection of CDC did not affect glucose levels, but completely attenuated the diabetes-related increases in the 12(S)-HETE content, p16<sup>ink4a</sup> expression, p-p38MAPK levels, glomerular volume, and the kidney/body weight ratio. Compared with levels in controls, p16<sup>ink4a</sup> and p-p38MAPK in the glomeruli derived from 12(S)-HETE-treated rats were significantly higher. <b><i>Conclusions:</i></b> 12-LO-p38MAPK mediates the upregulation of p16<sup>ink4a</sup> in HG-stimulated MCs and type 2-diabetic glomeruli, and new therapies aimed at 12-LO inhibition may prove beneficial in ameliorating diabetes-induced glomerular hypertrophy.
The aim of the present study was to examine the impacts and mechanisms of 12‑lipoxygenase (12‑LO) and its metabolites on the acetylation and methylation of histone‑3‑lysine (H3K) in the p21 gene. Rat mesangial cells (MCs) were selected for use in the present study. A chromatin immunoprecipitation assay, reverse transcription‑quantitative polymerase chain reaction analysis and a luciferase assay were used to detect transcriptional activities, the acetylation (Ac) of H3K (H3KAc), p21 promoter methylation (Me) and the transcription regions induced by 12 (S)‑hydroxyeicosatetraenoic acid (HETE). The cells were transfected to induce the overexpression of p300 to examine changes in 12 (S)‑HETE‑associated p21 regulation and epigenetic modifications. 12 (S)‑HETE enhanced p21 transcriptional activity and mRNA expression. In the promoter regions, P1 and P2, and the T1 transcription region, 12 (S)‑HETE induced significant H3K9 Ac and H3K4 Me1 epigenetic modifications, however, no changes were observed in the T2 region. By contrast, 12 (S)‑HETE treatment markedly prevented H3K9Me3 at the p21 promoter, suggesting that complex Me was involved in 12 (S)‑HETE‑associated p21 regulation. Furthermore, the overexpression of p300 markedly enhanced basal and 12 (S)‑HETE‑associated p21 transcriptional regulation in the MCs. 12 (S)‑HETE treatment also induced histone acetyltransferase p300 occupancy in the p21 promoter, and reduced the nuclear expression and occupancy of lysine‑specific demethylase (LSD1) in the p21 promoter. 12 (S)‑HETE induced p300 occupancy, and reduced the nuclear expression and occupancy of LSD1 in the p21 promoter. Therefore, enhanced H3K9Ac and H3K4Me1 in the p21 promoter and transcription regions, and decreased H3K9Me3 in the p21 promoter increased the expression of p21.
Fenofibrate (FF) protects against diabetic nephropathy (DN) in type 1 diabetic (T1D) mice by upregulating the expression of fibroblast growth factor 21 (FGF21), leading to the activation of the Akt-mediated Nrf2 antioxidant pathways. Here, we examined which isoforms of Akt contribute to FF activation of FGF21-mediated renal protection by examining the phosphorylation and expression of three isoforms, Akt1, Akt2, and Akt3. T1D induced by a single intraperitoneal dose of streptozotocin (STZ) resulted in reduced phosphorylation of one isoform, Akt2, but FF treatment increased renal Akt2 phosphorylation in these and normal mice, suggesting a potential and specific role for renal Akt2 in FF protection against T1D. This was further confirmed using in vitro cultured HK-2 human kidney tubule cells exposed to high glucose (HG) with siRNA silencing of the Akt2 gene and STZ-induced diabetic Akt2-knockout mice with and without 3-month FF treatment. In normal HK-2 cells exposed to HG for 24 hours, FF completely prevented cell death, reduced total Akt expression and glycogen synthase kinase (GSK)-3β phosphorylation, increased nuclear accumulation of Fyn, and reduced nuclear Nrf2 levels. These positive effects of FF were partially abolished by silencing Akt2 expression. Similarly, FF abolished T1D-induced renal oxidative stress, inflammation, and renal dysfunction in wild-type mice, but was only partially effective in Akt2-KO mice. Furthermore, FF treatment stimulated phosphorylation of AMPKα, an important lipid metabolism mediator, which in parallel with Akt2 plays an important role in FF protection against HG-induced HK-2 cells oxidative stress and damage. These results suggest that FF protects against DN through FGF21 to activate both Akt2/GSK-3β/Fyn/Nrf2 antioxidants and the AMPK pathway. Therefore, FF could be repurposed for the prevention of DN in T1D patients.
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