SARA suppresses myofibroblast precursor transdifferentiation in fibrogenesis in a mouse model of scleroderma

We previously reported that Smad anchor for receptor activation (SARA) plays a critical role in maintaining epithelial cell phenotype. Here, we show that SARA suppressed myofibroblast precursor transdifferentiation in a mouse model of scleroderma. Mice overexpressing SARA specifically in PDGFR-β+ pericytes and pan-leukocytes (SARATg) developed significantly less skin fibrosis in response to bleomycin injection compared with wild-type littermates (SARAWT). Single-cell RNA-Seq analysis of skin PDGFR-β+ cells implicated pericyte subsets assuming myofibroblast characteristics under fibrotic stimuli, and SARA overexpression blocked the transition. In addition, a cluster that expresses molecules associated with Th2 cells and macrophage activation was enriched in SARAWT mice, but not in SARATg mice, after bleomycin treatment. Th2-specific Il-31 expression was increased in skin of the bleomycin-treated SARAWT mice and patients with scleroderma (or systemic sclerosis, SSc). Receptor-ligand analyses indicated that lymphocytes mediated pericyte transdifferentiation in SARAWT mice, while with SARA overexpression the myofibroblast activity of pericytes was suppressed. Together, these data suggest a potentially novel crosstalk between myofibroblast precursors and immune cells in the pathogenesis of SSc, in which SARA plays a critical role.

Staphylococcus aureus-Associated Glomerulonephritis and Chronic Granulomatous Disease in an Adolescent Male

Staphylococcus-associated glomerulonephritis (GN) is an uncommon diagnosis in pediatric patients. Empiric therapy with steroids alone could potentially worsen the underlying infectious process in these patients, leading to worse clinical outcomes. An adolescent male diagnosed with GN was subsequently found to have chronic granulomatous disease with a Staphylococcus aureus liver abscess. His GN improved with antibiotics alone. This case illustrates the need to consider chronic infection, and primary immunodeficiency, in the differential diagnosis for new-onset GN.

Interleukin-6 Contributes to the Development of Anemia in Juvenile CKD

Introduction

Anemia is a common complication of chronic kidney disease (CKD) in children; however, the role of inflammation in its pathogenesis remains incompletely understood.

Methods

To elucidate the role of interleukin (IL)-6 in renal anemia, we induced CKD by adenine diet in juvenile wild-type (WT) and IL-6 deficient (Il6KO) mice, and examined serum IL-6 and relevant parameters in children with CKD.

Results

WT-CKD mice developed anemia despite increases in serum erythropoietin and displayed low serum iron and elevated serum IL-6. IL-6 deficiency resulted in a significant improvement of red blood cell count and hemoglobin in CKD mice. This effect was associated with improvement of hypoferremia by Il6 deletion, likely mediated by hepcidin. However, correction of hypoferremia by oral iron supplementation in WT-CKD mice did not fully replicate the protective effects of Il6 deletion, suggesting an additional iron-independent role for IL-6 in CKD-anemia. Indeed, Il6 deletion mitigated the severity of renal fibrosis and alleviated relative erythropoietin insufficiency in CKD mice. Cytokine profiling in a pediatric CKD cohort demonstrated that of 10 cytokines (IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, tumor necrosis factor (TNF)-α, and interferon-γ), only IL-6 was significantly (inversely) associated with hemoglobin when adjusted for glomerular filtration rate (GFR). The association between IL-6 and hemoglobin in children with CKD remained significant after adjustment for CKD stage, iron therapy, and hepcidin.

Discussion

IL-6 contributes to development of anemia in juvenile CKD, through mechanisms that include induction of hypoferremia, aggravation of renal fibrosis, and alteration of the erythropoietin axis. IL-6 appears to be a promising therapeutic target in the management of CKD-anemia.

Idiopathic renal replacement lipomatosis

Renal replacement lipomatosis (RRL) is a rare disorder which exhibits extensive proliferation of fatty tissue within the renal sinus, hilum, and perirenal region. The pathogenesis of this entity is unknown, though association with aging, renal atrophy, longstanding chronic urinary infections has been noted. Although imaging modalities may suggest the diagnosis of this entity, it is histopathology that clinches the diagnosis most accurately. We report a case of a 52 year old male who presented with nonfunctioning kidney and was histopathologically confirmed to be a case of renal replacement lipomatosis.

Partitioning-Defective 1a/b Depletion Impairs Glomerular and Proximal Tubule Development

The kidney is a highly polarized epithelial organ that develops from undifferentiated mesenchyme, although the mechanisms that regulate the development of renal epithelial polarity are incompletely understood. Partitioning-defective 1 (Par1) proteins have been implicated in cell polarity and epithelial morphogenesis; however, the role of these proteins in the developing kidney has not been established. Therefore, we studied the contribution of Par1a/b to renal epithelial development. We examined the renal phenotype of newborn compound mutant mice carrying only one allele of Par1a or Par1b. Loss of three out of four Par1a/b alleles resulted in severe renal hypoplasia, associated with impaired ureteric bud branching. Compared with kidneys of newborn control littermates, kidneys of newborn mutant mice exhibited dilated proximal tubules and immature glomeruli, and the renal proximal tubular epithelia lacked proper localization of adhesion complexes. Furthermore, Par1a/b mutants expressed low levels of renal Notch ligand Jag1, activated Notch2, and Notch effecter Hes1. Together, these data demonstrate that Par1a/b has a key role in glomerular and proximal tubule development, likely via modulation of Notch signaling.

Memantine protects rats treated with intrathecal methotrexate from developing spatial memory deficits

PURPOSE

To test whether memantine can prevent methotrexate-induced cognitive deficits in a preclinical model.

EXPERIMENTAL DESIGN

After noting that methotrexate exposure induces prolonged elevations of the glutamate analog homocysteic acid (HCA) within cerebrospinal fluid, we tested whether intrathecal injection of HCA would produce memory deficits similar to those observed after intrathecal methotrexate. We then tested whether memantine, an antagonist of the N-methyl-d-aspartate (NMDA) subclass of glutamate receptors, could protect animals treated with clinically relevant doses of intrathecal methotrexate against developing memory deficits. Finally, we asked whether memantine affected this pathway beyond inhibiting the NMDA receptor by altering expression of the NMDA receptor or affecting concentrations of HCA or glutamate within the central nervous system.

RESULTS

Four intrathecal doses of methotrexate induced deficits in spatial memory, persisting at least one month following the final injection. Intrathecal HCA was sufficient to reproduce this deficit. Concurrent administration of memantine during the period of methotrexate exposure was protective, decreasing the incidence of methotrexate-induced spatial memory deficits from 56% to 20% (P < 0.05). Memantine neither altered expression of NMDA receptors within the hippocampus nor blunted the methotrexate-induced increases in glutamate or HCA.

CONCLUSIONS

Excitotoxic glutamate analogs including HCA contribute to cognitive deficits observed after intrathecal methotrexate. Memantine, an NMDA receptor antagonist, reduces the incidence of cognitive deficits in rats treated with intrathecal methotrexate, and may therefore benefit patients with cancer receiving similar treatment.

Comparative analysis of the 100 kb region containing the Pi-k(h) locus between indica and japonica rice lines

We have recently cloned a pathogen inducible blast resistance gene Pi-k^h from the indica rice line Tetep using a positional cloning approach. In this study, we carried out structural organization analysis of the Pi-k^h locus in both indica and japonica rice lines. A 100 kb region containing 50 kb upstream and 50 kb downstream sequences flanking to the Pi-k^h locus was selected for the investigation. A total of 16 genes in indica and 15 genes in japonica were predicted and annotated in this region. The average GC content of indica and japonica genes in this region was 53.15% and 49.3%, respectively. Both indica and japonica sequences were polymorphic for simple sequence repeats having mono-, di-, tri-, tetra-, and pentanucleotides. Sequence analysis of the specific blast resistant Pi-k^h allele of Tetep and the susceptible Pi-k^h allele of the japonica rice line Nipponbare showed differences in the number and distribution of motifs involved in phosphorylation, resulting in the resistance phenotype in Tetep.

High-resolution mapping, cloning and molecular characterization of the Pi-k ( h ) gene of rice, which confers resistance to Magnaporthe grisea

In order to understand the molecular mechanisms involved in the gene-for-gene type of pathogen resistance, high-resolution genetic and physical mapping of resistance loci is required to facilitate map-based cloning of resistance genes. Here, we report the molecular mapping and cloning of a dominant gene (Pi-k ( h )) present in the rice line Tetep, which is associated with resistance to rice blast disease caused by Magnaporthe grisea. This gene is effective against M. grisea populations prevalent in the Northwestern Himalayan region of India. Using 178 sequence tagged microsatellite, sequence-tagged site, expressed sequence tag and simple sequence repeat (SSR) markers to genotype a population of 208 F(2) individuals, we mapped the Pi-k ( h ) gene between two SSR markers (TRS26 and TRS33) which are 0.7 and 0.5 cM away, respectively, and can be used in marker-assisted-selection for blast-resistant rice cultivars. We used the markers to identify the homologous region in the genomic sequence of Oryza sativa cv. Nipponbare, and a physical map consisting of two overlapping bacterial artificial chromosome and P1 artificial chromosome clones was assembled, spanning a region of 143,537 bp on the long arm of chromosome 11. Using bioinformatic analyses, we then identified a candidate blast-resistance gene in the region, and cloned the homologous sequence from Tetep. The putative Pi-k ( h ) gene cloned from Tetep is 1.5 kbp long with a single ORF, and belongs to the nucleotide binding site-leucine rich repeat class of disease resistance genes. Structural and expression analysis of the Pi-k ( h ) gene revealed that its expression is pathogen inducible.

Butyrate enema therapy stimulates mucosal repair in experimental colitis in the rat

BACKGROUND

The short chain fatty acid (SCFA) butyrate provides energy for colonocytes, stimulates colonic fluid and electrolyte absorption and is recognised as an effective treatment for multiple types of colitis.

AIM

To examine the impact of butyrate enema therapy on the clinical course, severity of inflammation, and SCFA stimulated Na+ absorption in a chronic experimental colitis.

METHODS

Distal colitis was induced in rats with a trinitrobenzenesulphonic acid (TNBS) enema. Five days after induction, rats were divided into groups to receive: no treatment, saline enemas, or 100 mM Na-butyrate enemas daily. On day 24, colonic damage score and tissue myeloperoxidase (MPO) activity were evaluated. Colon was mounted in Ussing chambers and Na+ transport and electrical activities were measured during a basal period and after stimulation with 25 mM butyrate.

RESULTS

In the untreated and the saline enema treated TNBS groups, diarrhoea and extensive colonic damage were seen, associated with increased tissue MPO activities and absent butyrate stimulated Na+ absorption. In contrast, in the butyrate enema treated TNBS group, diarrhoea ceased, colonic damage score improved, and tissue MPO activity as well as butyrate stimulated Na+ absorption recovered to control values.

CONCLUSION

Butyrate enema therapy stimulated colonic repair, as evidenced by clinical recovery, decreased inflammation, and restoration of SCFA stimulated electrolyte absorption.

Inhibition of short-chain fatty acid absorption and Na+ absorption during acute colitis in the rabbit

BACKGROUND/AIMS

Short-chain fatty acids (SCFAs) provide energy for colonocytes and stimulate colonic fluid and electrolyte absorption. The impact of acute colitis on SCFA-stimulated Na+ absorption and SCFA absorption was examined.

METHODS

Proximal colon from rabbits infected with Yersinia entercolitica, a pair-fed group, and controls was mounted in Ussing chambers, and Na+ transport, short-circuit current, and tissue conductance were examined during a basal period and after stimulation with the SCFAs, butyrate, or propionate. Propionate transport and luminal SCFA concentration were evaluated.

RESULTS

Butyrate and propionate stimulated electroneutral Na+ absorption above basal levels in the control and pair-fed groups, as evidenced by significant increases in mucosal-to-serosal and net Na+ fluxes with no change in serosal-to-mucosal flux, short-circuit current, or conductance. Butyrate-stimulated Na+ absorption and propionate absorption were blocked by amiloride, an inhibitor of Na(+)-H+ exchange. In the infected group, both butyrate and propionate failed to stimulate colonic Na+ absorption above basal levels. Propionate absorption was inhibited, and epinephrine failed to stimulate Na+ or propionate absorption. Luminal SCFA concentrations were increased in acute colitis.

CONCLUSIONS

Inhibition of SCFA-stimulated Na(+)-H+ exchange and SCFA absorption contribute to the diarrheal fluid loses observed in acute colitis and may reduce colonocyte energy supply.