Hua-feng Liu

Autophagy activation reduces renal tubular injury induced by urinary proteins.

Autophagy is shown to be beneficial for renal tubular injury caused by nephrotoxic drugs. To investigate whether autophagy could protect renal tubular epithelial cells (TECs) from injury induced by urinary proteins, we studied the activity and action of autophagy in TECs after urinary protein overload in vivo and in vitro. We found that autophagic vacuoles increased in TECs from patients with minimal change nephrotic syndrome (MCNS) and rat models with severe proteinuria induced by cationic BSA. In HK-2 cells, exposure to urinary proteins extracted from patients with MCNS led to a significant increase in autophagosome and autolysosome formation and decrease in SQSTM1/p62 protein level. Urinary protein addition also induced lysosomal turnover of LC3-II and perinuclear clustering of lysosomes. These changes were mediated by a reactive oxygen species (ROS)-dependent mechanism. Furthermore, pretreatment of HK-2 cells with rapamycin reduced the production of LCN2/NGAL and HAVCR1/KIM-1 and the level of apoptosis induced by urinary proteins. In contrast, blocking autophagy with chloroquine or BECN1 siRNAs exerted an opposite effect. Similar results were also observed in animal models with proteinuria after treatments with rapamycin and chloroquine. Taken together, our results indicated an increase in autophagic flux, which mounts an adaptive response in TECs after urinary protein overload.

Autophagy-lysosome pathway in renal tubular epithelial cells is disrupted by advanced glycation end products in diabetic nephropathy

Background: The pathophysiological importance of autophagy in renal tubules during the development of diabetic nephropathy (DN) has been implicated. Results: Autophagy was inactivated because lysosomal membrane permeabilization and lysosomal dysfunction were triggered by advanced glycation end products. Conclusion: The autophagy-lysosome pathway is disrupted in renal tubules in DN. Significance: The findings open a new field for studying the mechanisms of DN. It has been suggested that autophagy protects renal tubular epithelial cells (TECs) from injury in diabetic nephropathy (DN). However, the manner in which the autophagy-lysosome pathway is changed in this state remains unclear. In this study of DN, we investigated the autophagic activity and lysosomal alterations in vivo and in vitro. We found that autophagic vacuoles and SQSTM1-positive proteins accumulated in TECs from patients with DN and in human renal tubular epithelial cell line (HK-2 cells) treated with advanced glycation end products (AGEs), the important factors that involved in the pathogenesis of DN. In HK-2 cells, exposure to AGEs caused a significant increase in autophagosomes but a marked decrease in autolysosomes, and the lysosomal turnover of LC3-II was not observed, although LC3-II puncta were co-localized with the irregular lysosomal-associated membrane protein1 granules after AGEs treatment. Furthermore, lysosomal membrane permeabilization was triggered by AGEs, which likely resulted in a decrease in the enzymatic activities of cathepsin B and cathepsin L, the defective acidification of lysosomes, and suppression of the lysosomal degradation of DQ-ovalbumin. Oxidative stress evoked by AGEs-receptor for AGE interaction likely played an important role in the lysosomal dysfunction. Additionally, ubiquitinated proteins were co-localized with SQSTM1-positive puncta and accumulated in HK-2 cells after exposure to AGEs, indicating blocked degradation of SQSTM1-positive and ubiquitinated aggregates. Taken together, the results show that lysosomal membrane permeabilization and lysosomal dysfunction are triggered by AGEs, which induce autophagic inactivation in TECs from patients with DN. Disruption of the autophagy-lysosome pathway should be focused when studying the mechanisms underlying DN.

GSK-3β controls autophagy by modulating LKB1-AMPK pathway in prostate cancer cells.

Glycogen synthase kinase 3β (GSK3B, GSK‐3β) is a multi‐functional protein kinase involved in various cellular processes and its activity elevates after serum deprivation. We have shown that inhibition of GSK‐3β activity triggered a profound autophagic response and subsequent necrotic cell death after serum deprivation in prostate cancer cells. In this study, we dissected the mechanisms involved in GSK‐3β inhibition‐triggered autophagy.

Urinary proteins induce lysosomal membrane permeabilization and lysosomal dysfunction in renal tubular epithelial cells

Lysosomal membrane permeabilization (LMP) has been shown to cause the release of cathepsins and other hydrolases from the lysosomal lumen to the cytosol and initiate a cell death pathway. Whether proteinuria triggers LMP in renal tubular epithelial cells (TECs) to accelerate the progression of renal tubulointerstitial injury remains unclear. In the present study, we evaluated TEC injury as well as changes in lysosomal number, volume, activity, and membrane integrity after urinary protein overload in vivo and in vitro. Our results revealed that neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 levels were significantly increased in the urine of patients with minimal change nephrotic syndrome (MCNS) and the culture supernatant of HK-2 cells treated by urinary proteins extracted from MCNS patients. Urinary protein overload also induced apoptotic cell death in HK-2 cells. Importantly, we found that lysosomal volume and number were markedly increased in TECs of patients with MCNS and HK-2 cells overloaded with urinary proteins. However, lysosome function, as assessed by proteolytic degradation of DQ-ovalbumin and cathepsin-B and cathepsin-L activities, was decreased in HK-2 cells overloaded with urinary proteins. Furthermore, urinary protein overload led to a diffuse cytoplasmic immunostaining pattern of cathepsin-B and irregular immunostaining of lysosome-associated membrane protein-1, accompanying a reduction in intracellular acidic components, which could be improved by pretreatment with antioxidant. Taken together, our results indicate that overloading of urinary proteins caused LMP and lysosomal dysfunction at least partly via oxidative stress in TECs.

Update on the role of autophagy in systemic lupus erythematosus: A novel therapeutic target

Systemic lupus erythematosus (SLE), induced by the interaction of susceptibility genes and environment risk factors, is a classical autoimmune diseases characterized by the dysregulation of innate and adaptive immune systems. Recently, evidence from genetic, cell biology and animal models suggested autophagy, a major pathway for organelle and protein turnover, plays a pivotal role in the occurrence and development of SLE, but not yet fully elucidated. We summarized an update on the recognized key principles of autophagy in SLE and focused our attention on the role of autophagy, including two main signaling pathways including mTOR and Beclin-1, in immune cells, such as B cell, T cell, neutrophils, etc. in SLE. Also, effects of currently used biological and chemical therapeutic drugs on autophagy in SLE were discussed. Autophagy may provide new targets for both diagnostic and therapeutic approaches for SLE although some results are still controversial, which worth more in-depth discussion in the future.

Basophil Activation-Dependent Autoantibody and Interleukin-17 Production Exacerbate Systemic Lupus Erythematosus

Objective Autoantibody and inflammatory cytokines play crucial roles in the development of systemic lupus erythematosus (SLE); however, the regulation of their production warrants further investigation. This study aimed to investigate the role of basophil activation in the development of SLE based on studies in patients with SLE and spontaneous lupus-prone MRL-lpr/lpr mice. Methods The phenotypes of peripheral basophils and the production of autoantibody and interleukin (IL)-17 in patients with SLE were determined by flow cytometry and enzyme-linked immunosorbent assay, and also their correlations were investigated by statistical analysis. Thereafter, the effect of basophils on autoantibody production by B cells and Th17 differentiation in SLE were evaluated in vitro. Finally, the effect of basophil depletion on the development of autoimmune disorders in spontaneous lupus-prone MRL-lpr/lpr mice was examined. Results The decreased numbers and an increased activation of peripheral basophils were found to be correlated with increased autoantibody production and disease activity in patients with SLE. Correspondingly, in vitro coculture studies showed that basophils obtained from patients with SLE promoted autoantibody production by SLE B cells and promoted Th17 differentiation from SLE naïve CD4+ T cells. The decrease of peripheral basophils in patients with SLE might be due to their migration to lymph nodes post their activation mediated by (autoreactive) IgE as supported by their increased CD62L and CCR7 expressions and accumulation in the lymph nodes of MRL-lpr/lpr mice. Furthermore, an increased activation of peripheral basophils was identified in MRL-lpr/lpr mice. Importantly, basophil-depleted MRL-lpr/lpr mice exhibited an extended life span, improved renal function, and lower serum levels of autoantibodies and IL-17, while basophil-adoptive-transferred mice exhibited the opposite results. Conclusion These finding suggest that basophil activation-dependent autoantibody and IL-17 production may constitute a critical pathogenic mechanism in SLE.

Effects of Red Blood Cell Lysing Solutions on the Detection of Peripheral Basophils of Healthy Normals and Sle Patients by Flow Cytometry

To evaluate the effect of four widely used red blood cell lysing solutions on counting and measurement of activation marker of peripheral basophils in normals and systemic lupus erythematosus (SLE) patients by flow cytometry. Our results showed that the light scatter properties including FS and SS value of leukocytes in whole blood were preserved when whole blood samples were lysed in RBC Lysis Buffer and FACS Lysing Solution, while were affected when lysed in distilled water or ACK. By counting basophils, RBC Lysis Buffer and FACS Lysing Solution were almost the same level, while were significantly lower when lysed in distilled water or ACK. The expressions of CD203c on peripheral basophils of SLE patients were significantly higher than those of normals. Comparing the data of CD203c expression obtained demonstrated that there were no significant differences among them, while FACS Lysing Solution treatment leads to a slightly lower staining intensity of CD203c. We provide a solid description that the widely used red blood cell lysing reagents may influence the light scatter properties of leukocytes, the accuracy of quantity of absolute number of the existence of basophil subsets and the quantity of staining intensity of cell-activated marker CD203c fluorescence when measured by flow cytometry.

Geographical distribution, a risk factor for the incidence of lupus nephritis in China

BackgroundGeographical variation in lupus nephritis epidemiology may indicate important environmental factors contributions to the etiology of lupus nephritis. This paper first describes the epidemiology of biopsy-proven lupus nephritis in China by performing a systematic literature review and the possible social-environmental influential factors.MethodsThe keywords “lupus nephritis”, “renal biopsy” and “systemic lupus erythematous” were searched in the three largest Chinese electronic databases and Medline/PubMed. The data of the patients with biopsy-proven lupus nephritis were extracted. The possible environmental influential factors including the population density, ethnic group populations, the ratio of females to males, the average sunshine per year, annual average temperature and annual relative humidity, in different regions of China were analyzed.ResultsForty-one study centers with 34574 renal disease patients, and 3699 lupus nephritis patients met the inclusion criteria. Lupus nephritis accounts for 2.37% to 25% of all renal disease and 27.2% to 80.65% of renal disease associated with secondary glomerular diseases. The male-to-female ratio is approximately 1:5 in lupus nephritis patients. The included period is predominantly from 1995 to 2010. The proportion ratio of biopsy-proven lupus nephritis in all renal disease or in secondary glomerular disease significantly increased with decreasing latitude from the north to the south part of China. The population is predominantly Han Chinese.ConclusionsGeographical distribution appears to be a risk factor for the incidence of biopsy-proven LN in China.

Sulodexide Protects Renal Tubular Epithelial Cells from Oxidative Stress-Induced Injury via Upregulating Klotho Expression at an Early Stage of Diabetic Kidney Disease

The hypoalbuminuric effect of sulodexide (SDX) on diabetic kidney disease (DKD) was suggested by some clinical trials but was denied by the Collaborative Study Group. In this study, the diabetic rats were treated with SDX either from week 0 to 24 or from week 13 to 24. We found that 24-week treatment significantly decreased the urinary protein and HAVCR1 excretion, inhibited the interstitial expansion, and downregulated the renal cell apoptosis and interstitial fibrosis. Renoprotection was also associated with a reduction in renocortical/urinary oxidative activity and the normalization of renal klotho expression. However, all of these actions were not observed when SDX was administered only at the late stage of diabetic nephropathy (from week 13 to 24). In vitro, advanced glycation end products (AGEs) dose-dependently enhanced the oxidative activity but lowered the klotho expression in cultured proximal tubule epithelial cells (PTECs). Also, H2O2 could downregulate the expression of klotho in a dose-dependent manner. However, overexpression of klotho reduced the HAVCR1 production and the cellular apoptosis level induced by AGEs or H2O2. Our study suggests that SDX may prevent the progression of DKD at the early stage by upregulating renal klotho expression, which inhibits the tubulointerstitial injury induced by oxidative stress.

Basophil Recruitment to Skin Lesions of Patients with Systemic Lupus Erythematosus Mediated by CCR1 and CCR2

Background/Aims: Basophils have been reported to infiltrate skin lesions in various skin diseases, but not in systemic lupus erythematosus (SLE). This study investigated basophil infiltration in SLE and its mechanism. Methods: Twenty newly diagnosed SLE patients and twenty healthy controls were enrolled. Nine SLE patients underwent skin biopsies. Flow cytometric analysis the phenotype of peripheral basophils and their migration rate toward RANTES and MCP-1 were analyzed with the transwell culture system, also the expression of these two chemokines in skin tissue were analyzed with immunohistochemistry. Results: Increased activation and decreased numbers of peripheral basophils were observed in SLE patients compared with controls. Basophil migration into skin lesions of SLE patients were observed, but not in normal skin tissue. This migration was related to the upregulation of chemokine receptors CCR1 and CCR2 on basophils. In vitro studies showed that migration rate toward RANTES and MCP-1 increased significantly in basophils from SLE patients compared with those from controls. Consistently, high levels of RANTES and MCP-1 expression were observed in skin lesions from SLE patients but not in normal skin tissue. Conclusion: Basophil recruitment to skin lesions of SLE patients mediated by CCR1 and CCR2, which may contribute to tissue damage in SLE.