Suhua Jiang

Activation of the sigma receptor 1 suppresses NMDA responses in rat retinal ganglion cells

The sigma receptor 1 (σR1) has been shown to modulate the activity of several voltage- and ligand-gated channels. Using patch-clamp techniques in rat retinal slice preparations, we demonstrated that activation of σR1 by SKF10047 (SKF) or PRE-084 suppressed N-methyl-D-aspartate (NMDA) receptor-mediated current responses from both ON and OFF type ganglion cells (GCs), dose-dependently, and the effect could be blocked by the σR1 antagonist BD1047 or the σR antagonist haloperidol. The suppression by SKF of NMDA currents was abolished with pre-incubation of the G protein inhibitor GDP-β-S or the Gi/o activator mastoparan. We further explored the intracellular signaling pathway responsible for the SKF-induced suppression of NMDA responses. Application of either cAMP/the PKA inhibitor Rp-cAMP or cGMP/the PKG inhibitor KT5823 did not change the SKF-induced effect, suggesting the involvement of neither cAMP/PKA nor cGMP/PKG pathway. In contrast, suppression of NMDA responses by SKF was abolished by internal infusion of the phosphatidylinostiol-specific phospholipase C (PLC) inhibitor U73122, but not by the phosphatidylcholine-PLC inhibitor D609. SKF-induced suppression of NMDA responses was dependent on intracellular Ca2+ concentration ([Ca2+]i), as evidenced by the fact that the effect was abolished when [Ca2+]i was buffered with 10 mM BAPTA. The SKF effect was blocked by xestospongin-C/heparin, IP3 receptor antagonists, but unchanged by ryanodine/caffeine, ryanodine receptor modulators. Furthermore, application of protein kinase C inhibitors Bis IV and Gö6976 eliminated the SKF effect. These results suggest that the suppression of NMDA responses of rat retinal GCs caused by the activation of σR1 may be mediated by a distinct [Ca2+]i-dependent PLC-PKC pathway. This effect of SKF could help ameliorate malfunction of GCs caused by excessive stimulation of NMDA receptors under pathological conditions.

The balance of beneficial and deleterious effects of hypoxia-inducible factor activation by prolyl hydroxylase inhibitor in rat remnant kidney depends on the timing of administration

BACKGROUND Chronic hypoxia in the kidney has been suggested as a final common pathway in the progression of chronic kidney disease (CKD) leading to eventual kidney failure. Hypoxia-inducible factor (HIF) activation might offer a promising approach to the protection of hypoxic tissues, but the effect of HIF activation on CKD is still controversial. In this study, we investigated whether HIF activation had a beneficial or deleterious effect on CKD in the rat remnant kidney (RK) model. METHODS One week after a subtotal nephrectomy, rats were randomized and each received special administration of prolyl hydroxylases (PHD) inhibitor L-mimosine (L-Mim) as follows: in the early long-time L-Mim treatment group they were administered L-Mim at Weeks 2-12; in the advanced medium-term L-Mim treatment group they were administered L-Mim at Weeks 4-12 and in the end-stage L-Mim treatment group they were administered L-Mim at Weeks 8-12. RESULTS Compared with the control group, renal dysfunction and increased collagen III deposition, α-smooth muscle actin expression and ED-1-positive macrophage infiltration in tubulointerstitium were exacerbated by early long-term L-Mim treatment and improved by advanced medium-term L-Mim treatment. End-stage L-Mim treatment had no effect on RK rats. Furthermore, early long-term L-Mim treatment activated HIF-1α, connective tissue growth factor (CTGF) and phospho-Smad3 prominently throughout the time course and activated HIF-2α, vascular endothelial growth factor (VEGF) and erythropoietin (EPO) slightly at the end stage, while advanced medium-term L-Mim treatment activated HIF-2α, VEGF and EPO significantly and had no effect on HIF-1α, CTGF and phospho-Smad3. CONCLUSION HIF-α activation by PHD inhibitor L-Mim has dual roles in the development of CKD in the rat RK model depending on the timing of the administration and possibly the activated isoform of HIF-α.

Intermittent Exposure to Xenon Protects against Gentamicin-Induced Nephrotoxicity

Aminoglycoside antibiotics, especially gentamicin, are widely used to treat Gram-negative infections due to their efficacy and low cost. Nevertheless the use of gentamicin is limited by its major side effect, nephrotoxicity. Xenon (Xe) provided substantial organoprotective effects in acute injury of the brain and the heart and protected against renal ischemic-reperfusion injury. In this study, we investigated whether xenon could protect against gentamicin-induced nephrotoxicity. Male Wistar rats were intermittently exposed to either 70% xenon or 70% nitrogen (N2) balanced with 30% oxygen before and during gentamicin administration at a dose of 100 mg/kg for 7 days to model gentamicin-induced kidney injury. We observed that intermittent exposure to Xe provided morphological and functional renoprotection, which was characterized by attenuation of renal tubular damage, apoptosis, and oxidative stress, but not a reduction in inflammation. We also found that Xe pretreatment upregulated hypoxia-inducible factor 2α (HIF-2α) and its downstream effector vascular endothelial growth factor, but not HIF-1α. With regard to the three HIF prolyl hydroxylases, Xe pretreatment upregulated prolyl hydroxylase domain-containing protein-2 (PHD2), suppressed PHD1, and had no influence on PHD3 in the rat kidneys. Pretreatment with Xe also increased the expression of miR-21, a microRNA known to have anti-apoptotic effects. These results support Xe renoprotection against gentamicin-induced nephrotoxicity.

Diverse Effects of Ischemic Pretreatments on the Long-Term Renal Damage Induced by Ischemia-Reperfusion

Background/Aims: The role of ischemic pretreatment in long-term changes after renal ischemia-reperfusion (I/R) injury remains unknown. In this study, we mainly aimed to investigate the effect of ischemic pretreatments with different durations on the development of tubulointerstitial fibrosis and functional impairment following acute renal I/R. Methods: We established a rat model of renal warm I/R, clamping both pedicles for 40 min followed by reperfusion; the experiment was followed up for 10 weeks. Prior ischemia (10, 20, 30 min) was induced 8 days before the 40-min ischemia. To assess tissue fibrosis, we performed morphometric analysis, Masson’s trichrome and Sirius red staining. We also analyzed the expression of α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1) and phospho-Smad2. Results: Patchy tubulointerstitial fibrosis was found 5 and 10 weeks later in rats subjected to I/R alone or pretreated with 10-min ischemia. Tubulointerstitial fibrosis deteriorated further and renal dysfunction occurred in rats pretreated with 30-min ischemia accompanied by increased expression of α-SMA, TGF-β1, and phospho-Smad2 at 5 weeks. In contrast, the above abnormalities were significantly attenuated in rats pretreated with 20-min ischemia. Conclusion: Severe I/R injury may cause tubulointerstitial fibrosis in the long term, and different ischemic pretreatments have diverse effects on renal fibrosis.

Gene expression and protein distribution of orexins and orexin receptors in rat retina.

Orexins, composed of orexin A and orexin B, are identified as endogenous ligands of two orphan G-protein-coupled receptors: orexin 1 and orexin 2 receptors (OX1R and OX2R). Orexins are implicated in regulating wake/sleep states, feeding behaviors, etc. Using reverse transcription-polymerase chain reactive (RT-PCR) analysis and immunofluorescence double labeling, we investigated the distributions of orexin A, orexin B, OX1R and OX2R in rat retina. RT-PCR analysis revealed the presence of mRNAs of prepro-orexin, OX1R and OX2R in rat retina. Immunostaining for orexin A and orexin B was observed in many cells in the inner nuclear layer and the ganglion cell layer. In the outer retina, horizontal cells, labeled by calbindin, and bipolar cells, labeled by homeobox protein Chx10, were orexin A- and orexin B-positive. In the inner retina, two orexins were both found in GABAergic amacrine cells (ACs), including dopaminergic and cholinergic ones, stained by tyrosine hydroxylase and choline acetyltransferase respectively. Glycinergic ACs, including AII ACs, also expressed orexins. Weak to moderate labeling for orexin A and orexin B was diffusely distributed in the inner plexiform layer. Additionally, orexins were expressed in almost all ganglion cells (GCs) retrogradely labeled by cholera toxin B subunit. Specifically, double-labeling experiments demonstrated that melanopsin-positive GCs (intrinsically photosensitive retinal GCs, ipRGCs) were labeled by two orexins. Morever, OX1R immunoreactivity was observed in most of GCs and all dopaminergic ACs, as well as in both outer and inner plexiform layers. In contrast, no obvious OX2R immunostaining was detectable in the rat retina. These results suggest that orexins may modulate the function of neurons, especially in the inner retina. We further hypothesize that the orexin signaling via ipRGCs may be involved in setting the suprachiasmatic nucleus (SCN) circadian clock.

Plasma pentraxin 3 is associated with cardiovascular disease in hemodialysis patients.

Abstract This cross-sectional study evaluates the associations of Pentraxin 3 (PTX3) and cardiovascular disease (CVD) in hemodialysis (HD) patients. Plasma was obtained from 98 maintenance HD patients before and after a session of HD and 50 age-matched healthy subjects. We measured plasma PTX3 levels by enzyme-linked immunosorbent assay. Our results showed that plasma PTX3 levels were significantly higher in HD patients compared with controls (1.87 vs. 1.11 ng/mL, p < 0.001), and increased acutely after a single HD session (post-HD 2.18 ng/mL vs. pre-HD 1.87 ng/mL, p < 0.001). Patients with CVD had higher plasma PTX3 levels than those without CVD (2.18 vs. 1.76 ng/mL, p < 0.05). Plasma PTX3 levels correlated positively with cardiac troponin T (ρ = 0.287, p = 0.007) and carotid artery intima-media thickness (ρ = 0.294, p = 0.043). High plasma PTX3 (>1.87 ng/mL) level was positively and independently associated with CVD (OR = 3.15, p = 0.024). Receiver operator characteristics analysis showed the correlation between PTX3 and CVD more closely than high sensitivity C-reactive protein (hs-CRP) in patients whose hs-CRP were higher than 3 mg/L. The area under the curve for PTX3 and hs-CRP was 0.655 (p = 0.047) and 0.562 (p = 0.458), respectively. Moreover, plasma PTX3 levels correlated negatively with body mass index, hemoglobin, pre-albumin, total cholesterol, triglyceride, and low-density lipoprotein. These data support the main conclusions: PTX3 levels are markedly elevated in HD patients; HD procedure itself induces PTX3 elevation; plasma PTX3 is associated with CVD in maintenance HD patients.

Clinical value of urinary kidney biomarkers for estimation of renal impairment in elderly Chinese with essential hypertension

The purpose of this work was to observe the excretion of specific types of urinary proteins and urinary enzymes in elderly essential hypertension patients, for early detection and targeted treatment of hypertensive nephropathy in the elderly. A total of 120 elderly essential hypertensive patients and 38 healthy elderly volunteers were involved. The urinary excretion rate of retinal‐binding protein (RBP), transferrin (Tf), albumin (Alb), and urinary enzyme N‐acetyl‐beta‐D‐glucosaminidase (NAG) activity were determined. Patients were divided into two groups according to their creatinine clearance (Cockroft‐Gault formula). There were 88 patients in group A, whose glomerular filtration rate (GFR) was ≥80 mL/min, and 32 patients in group B with a GFR <80 mL/min. Among the essential hypertensive patients, urinary excretion rates of RBP, Alb, Tf, and NAG were increased in both groups compared with the healthy controls. But the amount of urinary protein differed between group A and group B. The excretion rate of specific urinary protein and urinary enzyme had a positive relationship with the duration of course of hypertension. We believe that specific types of urinary proteins and urinary enzymes may be useful markers for early diagnosis of hypertensive nephropathy; they can also be regarded as a clinical indicator of the progression of hypertensive nephropathy, serving in the assessment of therapeutic effects. J. Clin. Lab. Anal. 22:86–90, 2008.

The Relationship between the Level of Serum Creatinine, Modified Diet and Renal Disease Formula, Cockcroft–Gault Formula, and Renal Tubulointerstitial Lesion

Objective: This study investigated the relationship between the levels of serum creatinine (SCr), the estimated glomerular filtration rate (eGFR), and the degree of tubulointerstitial injury. Methods: A total of 511 patients of Zhongshan hospital in China were hospitalized due to physical abnormalities and diagnosed with kidney disease by renal biopsy. The clinical and pathological data were retrospectively analyzed. The level of SCr was determined in all patients, and the eGFR was calculated with modification of diet in renal disease and Cockcroft–Gault formulae, whereas the renal histopathology was quantified according to the Katafuchi semi-quantitative standards. Results: With the aggravation of tubulointerstitial injury, SCr level increased and eGFR decreased gradually. The degree of tubulointerstitial lesion showed a positive correlation with SCr level and negative correlation with Cockcroft–Gault formula and modification of diet in renal disease (r = 0.627, −0.649, −0.626; p < 0.001). When the SCr was in the normal range, above 90% of the patients had various degrees of tubulointerstitial damage and 12.2% of the patients had moderate-to-severe tubulointerstitial lesions. The correlation between SCr level and tubulointerstitial damage became weak. Conclusions: The morphologic changes of tubulointerstitium are closely linked with renal function, but incompletely parallel. SCr in the abnormal range could be used to diagnose tubulointerstitial injury well. However, when the level of SCr was in the so-called normal range, eGFR by the modification of diet in renal disease or Cockcroft–Gault formula may be preferred to assess renal tubulointerstitial injury.

Silencing HIF-1α aggravates growth inhibition and necrosis of proximal renal tubular epithelial cell under hypoxia

Abstract The kidney is particularly susceptible to ischemia/hypoxia insult while dysfunction of proximal tubular epithelial cells (PTEC) is a primary pathologic hallmark in acute kidney injury. Hypoxia-inducible factor-1 (HIF-1) is a key regulator responsible for cellular hypoxic responses. Therefore, we investigated the effects of HIF-1 suppression, using small interference RNA (siRNA), upon the cell fate of PTEC under hypoxia, and explored the underlying possible molecular mechanism. Hypoxia was induced with hypoxia mimetic cobalt chloride. Our data showed that, in HIF-1α siRNA group, the HK-2 cells growth inhibition and necrosis became worse than those in hypoxia group. However, for apoptosis, no significant difference was observed between them. Consistent with the downregulation of HIF-1α in HIF-1α siRNA group, both mRNA and protein expression of glucose transporter-1 (Glut-1) and vascular endothelial growth factor (VEGF) also reduced more significantly than those in hypoxia group. In conclusion, silencing HIF-1α gene could aggravate growth inhibition and necrosis of PTEC under hypoxia. We provide evidence, from the opposite direction, that HIF-1 activation under hypoxia may facilitate adaptation and survival of proximal renal tubular cells, and the beneficial effects may be related to its downstream genes, such as Glut-1 and VEGF.