T cell responses in immune-mediated IgA nephropathy.

Immunoglobulin A nephropathy (IgAN) is a complex autoimmune disease with various underlying causes and significant clinical heterogeneity. There are large individual differences in its development, and the etiology and pathogenesis are still poorly understood. While it is known that immunobiological factors play a significant role in the pathophysiology of IgAN, the specific nature of these factors has yet to be fully elucidated. Numerous investigations have verified that cluster of differentiation 4+ (CD4+) and CD8+ T lymphocytes are involved in the immunopathogenesis of IgAN. Furthermore, certain data also point to γδT cells' involvement in the pathophysiology of IgAN. By thoroughly examining the mechanisms of action of these T cells in the context of IgAN, this review sheds light on the immunopathogenesis of the disease and its associated factors. The review is intended to provide reference value for the future research in this field and promising treatment clues for clinical patients.

Deciphering roles of protein post-translational modifications in IgA nephropathy progression and potential therapy.

Immunoglobulin A nephropathy (IgAN), one type of glomerulonephritis, displays the accumulation of glycosylated IgA in the mesangium. Studies have demonstrated that both genetics and epigenetics play a pivotal role in the occurrence and progression of IgAN. Post-translational modification (PTM) has been revealed to critically participate in IgAN development and progression because PTM dysregulation results in impaired degradation of proteins that regulate IgAN pathogenesis. A growing number of studies identify that PTMs, including sialylation, o-glycosylation, galactosylation, phosphorylation, ubiquitination and deubiquitination, modulate the initiation and progression of IgAN. Hence, in this review, we discuss the functions and mechanisms of PTMs in regulation of IgAN. Moreover, we outline numerous compounds that govern PTMs and attenuate IgAN progression. Targeting PTMs might be a useful strategy to ameliorate IgAN.

Phospholipase A2 receptor is associated with hypercoagulable status in membranous nephropathy: a narrative review.

Background and Objective: Membranous nephropathy (MN) is the pathology type with the highest incidence of thrombotic events in nephrotic syndrome (NS). While patients with MN are prone to developing thromboembolic complications, the specific mechanism remains unclear. Many studies have shown a high titer of PLA2R antibody aggravates proteinuria and hypoalbuminemia and predicts a lower likelihood of clinical remission in patients with PLA2R-associated MN. Proteinuria and hypoalbuminemia also increase the risk of thrombotic events. In our previous review, we found secretory phospholipase A2 (sPLA2) may act as a ligand for PLA2R, and binding of sPLA2 to PLA2R results in damage to podocytes. sPLA2 can promote the release of AA from membrane phospholipids, and AA is closely related to blood lipid levels and coagulation cascades. The objective of this study is to explain the relationship between phospholipase A2 receptor (PLA2R) and blood hypercoagulability in MN patients and the new theory that secretory phospholipase A2 (sPLA2) and arachidonic acid (AA) may play a role in regulating blood lipid levels and the coagulation cascade in patients with PLA2R-positive MN. Methods: Literature retrieval was conducted through China National Knowledge Infrastructure (CNKI) and PubMed. Abstract and Introduction information was then retrieved and the results from the literature searched, classified, and important information summarized. A conclusion was then reached, and a new standpoint put forward. Key Content and Findings: We discussed the role of PLA2R antibody and sPLA2 in hypercoagulability in patients with MN and analyzed the following four possible mechanisms: sPLA2 can combine with PLA2R and induce podocyte apoptosis; sPLA2 may promote the production of anti-PLA2R antibodies; sPLA2 may promote the release of AA from membrane phospholipids; and AA induces platelet aggregation. Conclusions: PLA2R may exacerbate hypercoagulability in patients with PLA2R-related MN, and sPLA2 plays an important role in the process.

Crosstalk of fibroblast growth factor 23 and anemia-related factors during the development and progression of CKD (Review).

Fibroblast growth factor 23 (FGF23) plays an important role in the development of chronic kidney disease-mineral bone disorder (CKD-MBD). Abnormally elevated levels of 1,25-dihydroxyvitamin D cause osteocytes to secrete FGF23, which subsequently induces phosphaturia. Recent studies have reported that iron deficiency, erythropoietin (EPO) and hypoxia regulate the pathways responsible for FGF23 production. However, the molecular mechanisms underlying the interactions between FGF23 and anemia-related factors are not yet fully understood. The present review discusses the associations between FGF23, iron, EPO and hypoxia-inducible factors (HIFs), and their impact on FGF23 bioactivity, focusing on recent studies. Collectively, these findings propose interactions between FGF23 gene expression and anemia-related factors, including iron deficiency, EPO and HIFs. Taken together, these results suggest that FGF23 bioactivity is closely associated with the occurrence of CKD-related anemia and CKD-MBD.

Effects of hypoxia on bone metabolism and anemia in patients with chronic kidney disease.

BACKGROUND: Abnormal bone metabolism and renal anemia seriously affect the prognosis of patients with chronic kidney disease (CKD). Existing studies have mostly addressed the pathogenesis and treatment of bone metabolism abnormality and anemia in patients with CKD, but few have evaluated their mutual connection. Administration of exogenous erythropoietin to CKD patients with anemia used to be the mainstay of therapeutic approaches; however, with the availability of hypoxia-inducible factor (HIF) stabilizers such as roxadustat, more therapeutic choices for renal anemia are expected in the future. However, the effects posed by the hypoxic environment on both CKD complications remain incompletely understood. AIM: To summarize the relationship between renal anemia and abnormal bone metabolism, and to discuss the influence of hypoxia on bone metabolism. METHODS: CNKI and PubMed searches were performed using the key words "chronic kidney disease," "abnormal bone metabolism," "anemia," "hypoxia," and "HIF" to identify relevant articles published in multiple languages and fields. Reference lists from identified articles were reviewed to extract additional pertinent articles. Then we retrieved the Abstract and Introduction and searched the results from the literature, classified the extracted information, and summarized important information. Finally, we made our own conclusions. RESULTS: There is a bidirectional relationship between renal anemia and abnormal bone metabolism. Abnormal vitamin D metabolism and hyperparathyroidism can affect bone metabolism, blood cell production, and survival rates through multiple pathways. Anemia will further attenuate the normal bone growth. The hypoxic environment regulates bone morphogenetic protein, vascular endothelial growth factor, and neuropilin-1, and affects osteoblast/osteoclast maturation and differentiation through bone metabolic changes. Hypoxia preconditioning of mesenchymal stem cells (MSCs) can enhance their paracrine effects and promote fracture healing. Concurrently, hypoxia reduces the inhibitory effect on osteocyte differentiation by inhibiting the expression of fibroblast growth factor 23. Hypoxia potentially improves bone metabolism, but it still carries potential risks. The optimal concentration and duration of hypoxia remain unclear. CONCLUSION: There is a bidirectional relationship between renal anemia and abnormal bone metabolism. Hypoxia may improve bone metabolism but the concentration and duration of hypoxia remain unclear and need further study.

Exploring Steric Effects of Zinc Complexes Bearing Achiral Benzoxazolyl Aminophenolate Ligands in Isoselective Polymerization of rac-Lactide.

A series of tridentate achiral benzoxazolyl-based aminophenolate zinc complexes, LZnN(SiMe3)2 (L = 2-{[benzoxazoly-CH2N(R3)-]CH2}-6-R1-4-R2-C6H2O, R1 = R2 = Cl, R3 = Bn (1); R1 = R2 = tBu, R3 = Bn (2); R1 = trityl, R2 = Me: R3 = Bn (3); R3 = phenethyl (4); R3 = 3-methylbutyl (7); R3 = n-hexyl (8); R3 = cyclopentyl (9); R3 = cyclooctyl (11); R3 = 1-adamantyl (12)), was synthesized via the reactions of Zn[N(SiMe3)2]2 and 1 equiv of the corresponding aminophenol proligands. All of the complexes were obtained as racemates, and the X-ray diffraction studies confirmed the monomeric structures of typical complexes 11 and 12, where the metal center is tetra-coordinated by three donors of the aminophenolate ligand and one silylamido group. All of the complexes proved to be efficient initiators for the ring-opening polymerization of rac-lactide ( rac-LA) at ambient temperature, and the polymerizations were better controlled in the presence of 2-propanol. The substituents on the ortho-position of the phenoxide unit of the ligand and the skeleton nitrogen atom show significant influences on the stereoselectivity of the corresponding complex toward the polymerization of rac-LA, leading to the production of heterotactic biased polylactide (PLA) by complexes 1 and 2 ( Pm = 0.40-0.44) and moderately to highly isotactic PLA by complexes 3-12 ( Pm = 0.74-0.89). Detailed mechanism studies and microstructure analysis of typical PLA samples revealed that these zinc initiators afforded isotactic stereoblock PLAs via a chain-end control mechanism, and there is no obvious polymer exchange process during the polymerization process.

Aluminum methyl, alkoxide and α-alkoxy ester complexes supported by 6,6'-dimethylbiphenyl-bridged salen ligands: synthesis, characterization and catalysis for rac-lactide polymerization.

The synthesis and characterization of aluminum alkyl and alkoxide complexes bearing racemic 6,6'-dimethylbiphenyl-bridged salen-type ligands, and their catalysis in the ring-opening polymerization (ROP) of rac-lactide are reported. Reactions of AlMe3 with various amounts of the proligands (6,6'-[(6,6'-dimethyl-[1,1'-biphenyl]-2,2'-diyl)bis(nitrylomethilidyne)]-bis(2-R(1)-4-R(2)-phenol): , R(1) = R(2) = Me; , R(1) = (t)Bu, R(2) = Me; , R(1) = R(2) = cumyl; , R(1) = Br, R(2) = (t)Bu) afforded the corresponding mono- and dinuclear aluminum methyl complexes [AlMe (), Al2Me4 ()]. Aluminum alkoxide complexes AlO(i)Pr (), AlOBn (), and α-alkoxy ester complexes Al(OCMe2CO2Me) (), Al[(S)-OCHMeCO2Me] () were prepared via in situ alcoholysis of the parent aluminum methyl complex with the corresponding alcohols. The molecular structures of mononuclear complexes , dinuclear complex , alkoxide complexes and α-alkoxy ester complexes were established by single-crystal X-ray diffraction studies. Two broad resonances at about 69-70 ppm and 25-41 ppm were observed in the (27)Al NMR spectra of complexes and , indicating the existence of both four- and five-coordinate aluminum centers in solution, which results from the dissociation of one N donor of the salen ligand, accompanied by an association and dissociation equilibrium of the carbonyl group of the α-alkoxy ester ligand to the aluminum center. Complex is also a rare example of an O-lactate model complex that mimics the first insertion of l-LA. All complexes were investigated for the ROP of rac-LA at 110 °C in toluene. The polymerization initiated by complexes in the presence of (i)PrOH showed living features, affording PLAs with narrow molecular weight distributions (PDIs = 1.03-1.05) and 65-73% isotacticities. Particularly, complex showed an "immortal" behavior for the polymerization of rac-LA in the presence of excess alcohol. Compared with the mononuclear counterparts, the tetra-coordinate dinuclear aluminum complexes enabled a few fold boosts in activity, but gave atactic PLAs with broadened PDIs.

ß-Tricalcium phosphate/poly(glycerol sebacate) scaffolds with robust mechanical property for bone tissue engineering.

Despite good biocompatibility and osteoconductivity, porous ß-TCP scaffolds still lack the structural stability and mechanical robustness, which greatly limit their application in the field of bone regeneration. The hybridization of ß-TCP with conventional synthetic biodegradable PLA and PCL only produced a limited toughening effect due to the plasticity of the polymers in nature. In this study, a ß-TCP/poly(glycerol sebacate) scaffold (ß-TCP/PGS) with well interconnected porous structure and robust mechanical property was prepared. Porous ß-TCP scaffold was first prepared with polyurethane sponge as template and then impregnated into PGS pre-polymer solution with moderate viscosity, followed by in situ heat crosslinking and freezing-drying process. The results indicated that the freezing-drying under vacuum process could further facilitate crosslinking of PGS and formation of Ca(2+)-COO(-) ionic complexing and thus synergistically improved the mechanical strength of the ß-TCP/PGS with in situ heat crosslinking. Particularly, the ß-TCP/PGS with 15% PGS content after heat crosslinking at 130°C and freezing-drying at -50°C under vacuum exhibited an elongation at break of 375±25% and a compressive strength of 1.73MPa, 3.7-fold and 200-fold enhancement compared to the ß-TCP, respectively. After the abrupt drop of compressive load, the ß-TCP/PGS scaffolds exhibited a full recovery of their original shape. More importantly, the PGS polymer in the ß-TCP/PGS scaffolds could direct the biomineralization of Ca/P from particulate shape into a nanofiber-interweaved structure. Furthermore, the ß-TCP/PGS scaffolds allowed for cell penetration and proliferation, indicating a good cytobiocompatibility. It is believed that ß-TCP/PGS scaffolds have great potential application in rigid tissue regeneration.