New renal drug development to face chronic renal disease

Upregulation of KLF14 expression attenuates kidney fibrosis by inducing PPARα-mediated fatty acid oxidation

Tubulointerstitial fibrosis (TIF) is essential during the development of end-stage kidney disease (ESKD) and is associated with the impairment of fatty acid oxidation (FAO). Kruppel-like factor 14 (KLF14) is an important gene in lipid metabolism, but its role in TIF remains unknown. TGF-β-stimulated HK-2 cells and mouse unilateral ureteral obstruction (UUO) were used as renal fibrosis models. The role of KLF14 in the process of renal fibrosis was verified by gene knockout mice, genetic or pharmacological interference in animal model and cell model respectively. In the current study, we found that KLF14 expression increased after activation of the TGF-β signaling pathway during TIF. In KLF14^-/- mice, more severe fibrosis was observed after unilateral ureteral obstruction (UUO) was induced. In human HK2 cells, knockdown of KLF14 led to more severe fibrosis induced by TGF-β1, while overexpression of KLF14 partially attenuated this process. Specifically, KLF14 deficiency decreased mitochondrial FAO activity, resulting in lipid accumulation. Thus, the energy supply to the cells was insufficient, finally resulting in TIF. We further proved that KLF14 could target peroxisome proliferator activated receptor alpha (PPARα) as a transcriptional activator. This study identified the upregulation of KLF14 expression in response to kidney stress during the process of fibrosis. Upon TIF, the activated TGF-β signaling pathway can enhance KLF14 expression, while the upregulation of KLF14 expression can decrease the degree of TIF by improving FAO activity in tubular epithelial cells and recovering the energy supply mediated by PPARα.

Transcription factor old astrocyte specifically induced substance is a novel regulator of kidney fibrosis

Prevention of kidney fibrosis is an essential requisite for effective therapy in preventing chronic kidney disease (CKD). Here, we identify Old astrocyte specifically induced substance (OASIS)/cAMP responsive element‐binding protein 3‐like 1 (CREB3l1), a CREB/ATF family transcription factor, as a candidate profibrotic gene that drives the final common pathological step along the fibrotic pathway in CKD. Although microarray data from diseased patient kidneys and fibrotic mouse model kidneys both exhibit OASIS/Creb3l1 upregulation, the pathophysiological roles of OASIS in CKD remains unknown. Immunohistochemistry revealed that OASIS protein was overexpressed in human fibrotic kidney compared with normal kidney. Moreover, OASIS was upregulated in murine fibrotic kidneys, following unilateral ureteral obstruction (UUO), resulting in an increase in the number of OASIS‐expressing pathological myofibroblasts. In vitro assays revealed exogenous TGF‐β1 increased OASIS expression coincident with fibroblast‐to‐myofibroblast transition and OASIS contributed to TGF‐β1–mediated myofibroblast migration and increased proliferation. Significantly, in vivo kidney fibrosis induced via UUO or ischemia/reperfusion injury was ameliorated by systemic genetic knockout of OASIS, accompanied by reduced myofibroblast proliferation. Microarrays revealed that the transmembrane glycoprotein Bone marrow stromal antigen 2 (Bst2) expression was reduced in OASIS knockout myofibroblasts. Interestingly, a systemic anti‐Bst2 blocking antibody approach attenuated kidney fibrosis in normal mice but not in OASIS knockout mice after UUO, signifying Bst2 functions downstream of OASIS. Finally, myofibroblast‐restricted OASIS conditional knockouts resulted in resistance to kidney fibrosis. Taken together, OASIS in myofibroblasts promotes kidney fibrosis, at least in part, via increased Bst2 expression. Thus, we have identified and demonstrated that OASIS signaling is a novel regulator of kidney fibrosis.

LC-MS/MS assay for the determination of a novel anti-fibrotic candidate mefunidone in monkey plasma and its application to a pharmacokinetics study

Mefunidone (MFD) is a promising anti-fibrotic candidate molecule with greater anti-fibrotic activity than pirfenidone (PFD). However, there has been no report on the methodology used for the quantification of MFD or on any investigation of its pharmacokinetics. In this study, an efficient and reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to assay MFD in monkey plasma. This assay method was validated and applied to a pharmacokinetics study in monkeys. The lower limit of quantification of this assay was 0.1 μg·mL^-1 , and the linear calibration curve was acquired with R²  > 0.99 between 0.1 and 60 μg·mL^-1 . The intra-day and inter-day precision were evaluated with coefficient of variations of 1.5%-5.8%, whereas the mean accuracy ranged from 91.7% to 106.9%. A negligible matrix effect and good recovery were obtained using this assay, with average extraction recoveries of MFD and the internal standard (IS) in the range of 85.5%-124.8% and 84.1%-94.0%, respectively. The precision of the absolute matrix effect of MFD and the IS was 1.2-3.0% and 1.2-7.3%, respectively. The samples were stable under all experimental conditions. Linear pharmacokinetics were observed for MFD in monkeys, where the exposures of MFD increased proportionally with increasing MFD doses at the range of 10-90 mg·kg^-1 . Moderate elimination of MFD from the body was observed, with t_1/2 of 5-7 h, and the elimination rate of MFD was stable during multiple dosing. In conclusion, this method provides an reliable analytical approach for quantification of MFD in plasma and was successfully applied to a pharmacokinetics study in monkeys.

CD40 Generation 2.5 Antisense Oligonucleotide Treatment Attenuates Doxorubicin-induced Nephropathy and Kidney Inflammation

Preclinical and clinical data suggest CD40 activation contributes to renal inflammation and injury. We sought to test whether upregulation of CD40 in the kidney is a causative factor of renal pathology and if reduction of renal CD40 expression, using antisense oligonucleotides (ASOs) targeting CD40, would be beneficial in mouse models of glomerular injury and unilateral ureter obstruction. Administration of a Generation 2.5 CD40 ASO reduced CD40 mRNA and protein levels 75–90% in the kidney. CD40 ASO treatment mitigated functional, transcriptional, and pathological endpoints of doxorubicin-induced nephropathy. Experiments using an activating CD40 antibody revealed CD40 is primed in kidneys following doxorubicin injury or unilateral ureter obstruction and CD40 ASO treatment blunted CD40-dependent renal inflammation. Suborgan fractionation and imaging studies demonstrated CD40 in glomeruli before and after doxorubicin administration that becomes highly enriched within interstitial and glomerular foci following CD40 activation. Such foci were also sites of ASO distribution and activity and may be predominately comprised from myeloid cells as bone marrow CD40 deficiency sharply attenuated CD40 antibody responses. These studies suggest an important role of interstitial renal and/or glomerular CD40 to augment kidney injury and inflammation and demonstrate that ASO treatment could be an effective therapy in such disorders.