Translationally controlled tumour protein is associated with podocyte hypertrophy in a mouse model of type 1 diabetes

AIMS/HYPOTHESIS

Translationally controlled tumour protein (TCTP) is thought to be involved in cell growth by regulating mTOR complex 1 (mTORC1) signalling. As diabetes characteristically induces podocyte hypertrophy and mTORC1 has been implicated in this process, TCTP may have a role in the pathogenesis of diabetes-induced podocyte hypertrophy.

METHODS

We investigated the effects and molecular mechanisms of TCTP in diabetic mice and in high glucose-stimulated cultured podocytes. To characterise the role of TCTP, we conducted lentivirus-mediated gene silencing of TCTP both in vivo and in vitro.

RESULTS

Glomerular production of TCTP was significantly higher in streptozotocin induced-diabetic DBA/2J mice than in control animals. Double-immunofluorescence staining for TCTP and synaptopodin revealed that podocyte was the principal cell responsible for this increase. TCTP knockdown attenuated the activation of mTORC1 downstream effectors and the overproduction of cyclin-dependent kinase inhibitors (CKIs) in diabetic glomeruli, along with a reduction in proteinuria and a decrease in the sizes of podocytes as well as glomeruli. In addition, knockdown of TCTP in db/db mice prevented the development of diabetic nephropathy, as indicated by the amelioration of proteinuria, mesangial expansion, podocytopenia and glomerulosclerosis. In accordance with the in vivo data, TCTP inhibition abrogated high glucose-induced hypertrophy in cultured podocytes, which was accompanied by the downregulation of mTORC1 effectors and CKIs.

CONCLUSIONS/INTERPRETATION

These findings suggest that TCTP might play an important role in the process of podocyte hypertrophy under diabetic conditions via the regulation of mTORC1 activity and the induction of cell-cycle arrest.

Plasma protein profiles in early asthmatic responses to inhalation allergen challenge

Although mediators, such as lipids, cytokines, and chemokines, are related to the appearance of an IPR, there has been no reliable indicator to predict conditions for the appearance of an IPR. In this study, we adopted a proteomic approach to investigate the pathogenesis at the level of the plasma proteins and to develop plasma markers to predict the appearance of an IPR following an inhalation challenge with Dermatophagoides pteronyssinus (D.p.). Sixteen mild asthmatics were recruited. Plasma was obtained before challenge and when a decline in forced expiratory volume in 1 s (FEV(1)) values greater than 20% from the phosphate-buffered saline value was achieved during D.p. allergen challenge (positive responders), or at 60 min after the highest concentration of D.p. allergen was inhaled (negative responders). After comparing normalized volumes of the spots in the two groups, differentially expressed spots were identified using intra-gel digestion and mass spectrometric analysis. Before D.p. antigen challenge, four spots of gamma fibrinogen and its isoforms were significantly decreased and two spots of complement C3 fragments were significantly increased in the positive responders compared to the negative responders. After D.p. antigen challenge, complement C3 fragment was persistently higher, while gamma fibrinogen was lower in the positive responders than in the negative responders. A validation study using Western blotting showed that gamma fibrinogen expression in the IPR-positive asthmatics was significantly decreased compared to the average of the IPR-negative asthmatic control group. These results indicate that alterations in the complement cascade and fibrinogen may predispose patients to the appearance of an immediate response to D.p. allergen challenge and may provide plasma markers to predict the appearance of an IPR.

Association of angiotensin I-converting enzyme gene polymorphisms with aspirin intolerance in asthmatics

BACKGROUND

Aspirin-intolerant asthma (AIA) refers to the development of bronchoconstriction in asthmatic individuals following the ingestion of aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs). Angiotensin I-converting enzyme (ACE), a membrane-bound peptidase present in the lung, plays a pivotal role in the metabolism of the endogenous peptides involved in the pathogenesis of asthma.

METHODS

We screened a Korean asthma cohort (581 asthmatics including 81 aspirin-intolerant asthmatics and 231 aspirin-tolerant asthmatics, and 181 normal controls) for four single nucleotide polymorphisms (SNPs; -262 A>T and -115 T>C in the 5'-flanking region and +5467 T>C [Pro450Pro] and+11860 A>G [Thr776Thr] in the coding region) and one ins/del (+21288 CT) in the ACE gene.

RESULTS

None of the SNPs or haplotypes showed any association with the development of asthma, but they were significantly associated with the risk of AIA. Logistic regression indicated that the frequency of the rare alleles of -262 A>T and -115 T>C was higher in subjects with AIA than in subjects with aspirin-tolerant asthma (ATA) (P=0.003-0.01, P( corr)=0.015-0.05). Subjects homozygous for the rare alleles of -262 A>T and -115 T>C showed a greater decline in forced expiratory volume in 1 s (FEV(1)) after aspirin provocation than those homozygous for the common alleles (P<0.05). A luciferase reporter assay indicated that ACE promoters containing the rare -262 A>T allele possessed lower activity than did those containing the common allele (P=0.009). In addition, ACE promoters bearing the rare -115 T>C allele had no luciferase activity. DNA-protein binding assays revealed a band containing the ACE promoter region (including -262 A) and a protein complex.

CONCLUSION

The -262 A>T polymorphism in the promoter of the ACE gene is associated with AIA, and the rare allele of -262 A>T may confer aspirin hypersensitivity via the down-regulation of ACE expression.

Apolipoprotein E genotype in Korean schizophrenic patients

The apolipoprotein E (APOE) epsilon4 allele is a known risk factor for the development of Alzheimer's disease, however, an association of the APOE genotype with schizophrenia is controversial. We investigated the association in 60 Korean schizophrenic patients and 60 healthy controls. APOE genotypes were identified by reverse hybridization-based line probe assay. There were significant differences in the distribution of APOE genotypes between schizophrenic patients and controls. APOE epsilon2 and epsilon3 allele frequencies in schizophrenic patients were significantly different from those in controls. Our results suggest that APOE alleles seem to be operative in the pathogenesis of schizophrenic disorders.