Renal expression of hypoxia inducible factor-1α in patients with chronic kidney disease: a clinicopathologic study from nephrectomized kidneys.

BACKGROUND & OBJECTIVES: Hypoxia inducible factor-1α (HIF-1α) has been shown to play a role in the pathogenesis of renal interstitial fibrosis. However, the relationship of HIF-1α expression intensity in human renal tissue with the degree of renal function or renal fibrosis has not been investigated. We therefore, undertook this study to assess the relationship between HIF-1α expression and degree of renal impairment and renal fibrosis using renal tissue from nephrectomized kidneys from patients with chronic kidney disease. METHODS: This retrospective study was performed with 70 patients undergoing unilateral or bilateral nephrectomy because of renal cell carcinoma, urothelial cell carcinoma, or renal abscess. Immunohistochemical analysis of HIF-1α expression in non-tumourous or non-abscess renal parenchyma was performed. The patients were divided into two groups: group 1 (n=37) with low intensity HIF-1α expression and group 2 (n=33) with high intensity HIF-1α expression. RESULTS: The intensity of renal HIF-1α expression was significantly associated with serum creatinine level (P =0.005), estimated glomerular filtration rate (P=0.02), fibrosis score of the interstitium (P=0.004) and glomerular sclerosis (P=0.013). A high intensity of HIF-1α expression tended to be associated with lower serum creatinine, higher estimated glomerular filtration rate, low interstitial fibrosis score and low glomerular sclerosis. In addition, multivariate analysis by step-wise logistic regression demonstrated that interstitial fibrosis was the only independent factor associated with the intensity of renal HIF-1α expression (OR 4.107, CI 1.535-11.313, P=0.005). INTERPRETATION & CONCLUSIONS: This study demonstrated a correlation between intensity of HIF-1α expression and degree of renal interstitial fibrosis. The association demonstrated an elevated HIF-1α expression in less severe kidney disease. The intensity of HIF-1α renal expression plays a role in the pathogenesis of chronic kidney disease.

Coordination through Inhibition: Control of Stabilizing and Updating Circuits in Spatial Orientation Working Memory.

Spatial orientation memory plays a crucial role in animal navigation. Recent studies of tethered Drosophila melanogaster (fruit fly) in a virtual reality setting showed that the head direction is encoded in the form of an activity bump, i.e., localized neural activity, in the torus-shaped ellipsoid body (EB). However, how this system is involved in orientation working memory is not well understood. We investigated this question using free moving flies (D. melanogaster) in a spatial orientation memory task by manipulating two EB subsystems, C and P circuits, which are hypothesized for stabilizing and updating the activity bump, respectively. To this end, we suppressed or activated two types of inhibitory ring neurons (EIP and P) which innervate EB, and we discovered that manipulating the two inhibitory neuron types produced distinct behavioral deficits, suggesting specific roles of the inhibitory neurons in coordinating the stabilization and updating functions of the EB circuits. We further elucidate the neural mechanisms underlying such control circuits using a connectome-constrained spiking neural network model.

Increased expression of intranuclear matrix metalloproteinase 9 in atrophic renal tubules is associated with renal fibrosis.

BACKGROUND: Reduced turnover of extracellular matrix has a role in renal fibrosis. Matrix metalloproteinases (MMPs) is associated with many glomerular diseases, but the histological association of MMPs and human renal fibrosis is unclear. METHODS: This is a retrospective study. Institutional Review Board approval was obtained for the review of patients' medical records, data analysis and pathological specimens staining with waiver of informed consents. Specimens of forty-six patients were examined by immunohistochemical stain of MMP-9 in nephrectomized kidneys, and the association of renal expression of MMP-9 and renal fibrosis was determined. MMP-9 expression in individual renal components and fibrosis was graded as high or low based on MMP-9 staining and fibrotic scores. RESULTS: Patients with high interstitial fibrosis scores (IFS) and glomerular fibrosis scores (GFS) had significantly higher serum creatinine, lower estimated glomerular filtration rate (eGFR), and were more likely to have chronic kidney disease (CKD) and urothelial cell carcinoma. Univariate analysis showed that IFS and GFS were negatively associated with normal and atrophic tubular cytoplasmic MMP-9 expression and IFS was positively correlated with atrophic tubular nuclear MMP-9 expression. Multivariate stepwise regression indicated that MMP-9 expression in atrophic tubular nuclei (r = 0.4, p = 0.002) was an independent predictor of IFS, and that MMP-9 expression in normal tubular cytoplasm (r = -0.465, p<0.001) was an independent predictor of GFS. CONCLUSIONS: Interstitial fibrosis correlated with MMP-9 expression in the atrophic tubular nuclei. Our results indicate that renal fibrosis is associated with a decline of MMP-9 expression in the cytoplasm of normal tubular cells and increased expression of MMP-9 in the nuclei of tubular atrophic renal tubules.