Regulators of calcineurin 1 deficiency attenuates tubulointerstitial fibrosis through improving mitochondrial fitness.

Renal fibrosis is the common pathological process of various chronic kidney diseases (CKD). Recent studies indicate that mitochondrial fragmentation is closely associated with renal fibrosis in CKD. However, the molecular mechanisms leading to mitochondrial fragmentation remain to be elucidated. The present study investigated the role of regulators of calcineurin 1 (RCAN1) in mitochondrial fission and renal interstitial fibrosis using conditional knockout mice in which RCAN1 was genetically deleted in tubular epithelial cells (TECs). TEC-specific deletion of RCAN1 attenuated tubulointerstitial fibrosis and epithelial to mesenchymal transition (EMT)-like phenotype change after unilateral ureteral obstruction (UUO) and ischemia reperfusion injury (IRI) through suppressing TGF-ß1/Smad3 signaling pathway. TEC-specific deletion of RCAN1 also reduced the tubular apoptosis after UUO by inhibiting cytochrome c/caspase-9 pathway. Ultrastructure analysis revealed a marked decrease in mitochondrial fragmentation in TECs of RCAN1-deficient mice in experimental CKD models. The expression of mitochondrial profission proteins dynamin-related protein 1 (Drp1) and mitochondrial fission factor (Mff) was also downregulated in obstructed kidney of TEC-specific RCAN1-deficient mice. Furthermore, TEC-specific deletion of RCAN1 attenuated the dysfunctional tubular autophagy by regulating PINK1/Parkin-induced mitophagy in CKD. RCAN1 knockdown and knockout similarly improved the mitochondrial quality control in HK-2 cells and primary cultured mouse tubular cells stimulated by TGF-ß1. Put together, our data indicated that RCAN1 plays an important role in the progression of tubulointerstitial fibrosis through regulating the mitochondrial quality. Therefore, targeting RCAN1 may provide a potential therapeutic approach in CKD.

Dual roles of parathyroid hormone related protein in TGF-ß1 signaling and fibronectin up-regulation in mesangial cells.

Little is known about the cross-talk between parathyroid hormone (PTH) related protein (PTHrP) and TGF-ß1 in mesangial cells (MCs). Our results showed that PTHrP treatment (≤3 h) induced internalization of PTH1R (PTH/PTHrP receptor)-TßRII (TGF-ß type 2 receptor) complex and suppressed TGF-ß1-mediated Smad2/3 activation and fibronectin (FN) up-regulation. However, prolonged PTHrP treatment (12-48 h) failed to induce PTH1R-TßRII association and internalization. Total protein levels of PTH1R and TßRII were unaffected by PTHrP treatment. These results suggest that internalization of PTH1R and TßRII after short PTHrP treatment might not lead to their proteolytic destruction, allowing the receptors to be recycled back to the plasma membrane during prolonged PTHrP exposure. Receptor re-expression at the cell surface allows PTHrP to switch from its initial inhibitory effect to promote induction of FN. Our study thus demonstrates the dual roles of PTHrP on TGF-ß1 signaling and FN up-regulation for the first time in glomerular MCs. These data also provided new insights to guide development of therapy for diabetic kidney disease (DKD).

Effect of cold stress on immunity in rats.

An increase in the morbidity of upper respiratory tract infections and the attack and exacerbation of autoimmune diseases has been observed to occur in the few days following sudden environmental temperature decreases, but the mechanisms for these phenomena are not well understood. To determine the effect of a sudden ambient temperature drop on the levels of stress hormones and T-lymphocyte cytokines in the plasma, the Toll-like receptor 4 (TLR4) expression of immunocompetent cells in rat spleens and the levels of regulatory T (Treg) cells in the peripheral blood, Sprague Dawley rats were divided into three groups of different ambient temperatures (20, 4 and -12°C). In each group, there were four observation time-points (1, 12, 24 and 48 h). Each ambient temperature group was subdivided into non-stimulation, lipopolysaccharide-stimulation and concanavalin A-stimulation groups. The levels of adrenocorticotropin (ACTH), epinephrine (EPI), angiotensin-II (ANG-II), interleukin-2 (IL-2), interferon-γ (IFN-γ), IL-4 and IL-10 in the plasma were determined using ELISA. The cellular expression levels of TLR4 and the presence of cluster of differentiation (CD)4+CD25+ and CD4+CD25+Forkhead box P3 (Foxp3)+ cells were determined using flow cytometry. The experiments demonstrated that the ACTH, EPI, ANG-II and IL-10 levels in the plasma were significantly increased at 4 and -12°C compared with those at 20°C, while the plasma levels of IFN-γ, IL-2 and IL-4, the TLR4 expression rates of immunocompetent cells in the rat spleen and the percentage of CD4+CD25+Foxp3+ Treg cells among the CD4+CD25+ Treg cells in the peripheral blood were decreased at 4 and -12°C compared with those at 20°C. These data indicate that cold stress affects the stress hormones and the innate and adaptive immunity functions in rats.

[Effects of nitrogen application rates and straw returning on nutrient balance and grain yield of late sowing wheat in rice-wheat rotation].

Field experiments were conducted to study the effects of nitrogen application rates and straw returning on grain yield, nutrient accumulation, nutrient release from straw and nutrient balance in late sowing wheat. The results showed that straw returning together with appropriate application of nitrogen fertilizer improved the grain yield. Dry matter, nitrogen, phosphorus and potassium accumulation increased significantly as the nitrogen application rate increased. At the same nitrogen application rate (270 kg N · hm(-2)), the dry matter, phosphorus and potassium accumulation of the treatment with straw returning were higher than that without straw returning, but the nitrogen accumulation was lower. Higher-rate nitrogen application promoted straw decomposition and nutrient release, and decreased the proportion of the nutrient released from straw after jointing. The dry matter, phosphorus and potassium release from straw showed a reverse 'N' type change with the wheat growing, while nitrogen release showed a 'V' type change. The nutrient surplus increased significantly with the nitrogen application rate. At the nitrogen application rate for the highest grain yield, nitrogen and potassium were surplus significantly, and phosphorus input could keep balance. It could be concluded that as to late sowing wheat with straw returning, applying nitrogen at 257 kg · hm(-2) and reducing potassium fertilizer application could improve grain yield and reduce nutrients loss.

[Effects of nitrogen application rates on apparent soil nitrogen surplus of late sowing wheat with straw returning in rice-wheat rotation].

Field experiments were conducted to study the effects of varying rates of nitrogen application on soil mineral nitrogen content, amount of nitrogen released from the straw, and grain yield of late sowing wheat with straw returning. The result showed that a high nitrogen fertilizer application rate enhanced the mineral nitrogen content in the soil layer of 0 to 50 cm, and also in the lower soil layers when using N at 270 and 360 kg · hm(-2) with the advance of growth stages. The amount of nitrogen released form the straw increased as the nitrogen application rate increased; the lowest appeared from overwintering to jointing, and the highest from jointing to maturity. During the whole growing season, apparent nitrogen surplus occurred when the nitrogen application rate was higher than 180 kg · hm(-2). The N surplus before jointing was significantly higher than that from jointing to maturity. Grain yield reached the highest at a nitrogen application rate of 270 kg · hm(-2), and a higher application rate obviously decreased the nitrogen use efficiency. It could be concluded that applying nitrogen at 270 kg · him(-2) could improve the grain yield of late sowing wheat with straw returning with the optimal ecological benefit.