Gene expression profile in rat renal isografts from brain dead donors

Cobalt protoporphyrin protects the liver against apoptosis in rats of brain death

Brain death (BD) leads to a marked increase in apoptosis, which influences the viability of donor organs. Induction of heme oxygenase 1 (HO-1) has been shown to exert beneficial effects in different liver injury models. Therefore, we examined the effect of pretreating rats with cobalt protoporphyrin (CoPP), an HO-1 inducer, on apoptosis in liver during BD and elucidated the mechanisms involved. First, rats were killed at 0, 1, 2, 4 and 6 h after BD induction to examine the expression of hepatic HO-1. Second, rats were randomly divided into four groups (n=6): (S group) rats undergoing sham operation, (CS group) rats pretreated with CoPP for 24 h before the sham operation, (B group) rats undergoing BD for 6 h, (CB group) rats pretreated with CoPP for 24 h before BD induction. The expression levels of hepatic HO-1 mRNA and protein in rats increased at 0, 1, 2, 4 and 6h after BD induction, compared with sham operated rats. In the CB group compared with the B group, the increased hepatic expression of HO-1 correlated with a significant decrease in serum ALT/AST levels, fewer apoptotic cells in liver, increased hepatic expression of Mcl-1 and Bcl-2, and decreased hepatic expression of Bax, cytosolic cytochrome c and cleaved caspase-3. CoPP inhibits apoptosis in liver of BD rats in part via modulating the mitochondrial apoptosis pathway. HO-1 may serve as a potential target for improving the quality of organs from BD donors.

Meta-analysis of molecular response of kidney to ischemia reperfusion injury for the identification of new candidate genes

BACKGROUND

Accumulated to-date microarray data on ischemia reperfusion injury (IRI) of kidney represent a powerful source for identifying new targets and mechanisms of kidney IRI. In this study, we conducted a meta-analysis of gene expression profiles of kidney IRI in human, pig, rat, and mouse models, using a new scoring method to correct for the bias of overrepresented species. The gene expression profiles were obtained from the public repositories for 24 different models. After filtering against inclusion criteria 21 experimental settings were selected for meta-analysis and were represented by 11 rat models, 6 mouse models, and 2 models each for pig and human, with a total of 150 samples. Meta-analysis was conducted using expression-based genome-wide association study (eGWAS). The eGWAS results were corrected for a rodent species bias using a new weighted scoring algorithm, which favors genes with unidirectional change in expression in all tested species.

RESULTS

Our meta-analysis corrected for a species bias, identified 46 upregulated and 1 downregulated genes, of which 26 (55%) were known to be associated with kidney IRI or kidney transplantation, including LCN2, CCL2, CXCL1, HMOX1, ICAM1, ANXA1, and TIMP1, which justified our approach. Pathway analysis of our candidates identified "Acute renal failure panel" as the most implicated pathway, which further validates our new method. Among new IRI candidates were 10 novel (<5 published reports related to kidney IRI) and 11 new candidates (0 reports related to kidney IRI) including the most prominent candidates ANXA2, CLDN4, and TYROBP. The cross-species expression pattern of these genes allowed us to generate three workable hypotheses of kidney IRI, one of which was confirmed by an additional study.

CONCLUSIONS

Our first in the field kidney IRI meta-analysis of 150 microarray samples, corrected for a species bias, identified 10 novel and 11 new candidate genes. Moreover, our new meta-analysis correction method improved gene candidate selection by identifying genes that are model and species independent, as a result, function of these genes can be directly extrapolated to the disease state in human and facilitate translation of potential diagnostic or therapeutic properties of these candidates to the bedside.

Genomewide expression profiles of rat model renal isografts from brain dead donors

BACKGROUND

It has been well documented that two factors, brain death (BD) and ischemia/reperfusion (I/R) injury, have distinct but overlapping adverse influences on the clinical outcome of renal transplantation.

METHOD

We previously established a rat model of renal isografting from brain dead donors. In the present study, we performed genomic expression profiling with a high-density oligonucleotide microarray to identify genes that were upregulated or downregulated by BD and/or I/R injury.

RESULTS

Among a total of 20,550 genes, most of those upregulated by BD were genes for adhesion molecules and cytokines or for chemokines such as Gro1 and IP-10. When overexpression of these genes was assessed by real-time reverse transcriptase-polymerase chain reaction, it was only observed one hr after the engraftment of kidneys from BD donors and returned to baseline thereafter, indicating the presence of an acute systemic inflammatory response to BD. Analysis of biologic networks demonstrated the activation of specific pathways that were clearly different for BD and I/R injury. The p53 and NFkappaB pathway was involved in the acute response to BD, whereas the Myc, Jun, and c-fos pathway was involved in I/R injury. Investigation of secretory protein genes identified LCN2 and SPP1 as candidate genes for biologic markers.

CONCLUSION

Because our experimental system is a good model of renal transplantation from brain dead or living human donors, our data may be useful for elucidating the pathologic processes involved and for identification of novel markers for graft dysfunction of renal transplantation.

Up-Regulation of Osteopontin, Chemokines, Adhesion Molecule, and Heat Shock Proteins in 1-Hour Biopsy From Cardiac Death Donor Kidneys

AIMS

Since April 1979, 471 kidneys were retrieved from donors after cardiac death (DCD) using an in situ regional cooling technique, with excellent renal function and good long-term graft survival. However, the precise cascade of events following transplantation of DCD kidneys and the influence of ischemia-reperfusion injury remain unclear. In this study, we performed gene expression profiling using 1-hour biopsy samples from DCD kidneys versus those from living sources.

METHODS

All kidney grafts were procured at our center using an in situ regional cooling technique from DCD. Living donor kidneys (LD) were harvested by open nephrectomy. All graft biopsies were performed 1 hour after reperfusion (DCD n = 8, LD n = 9). We analyzed the expression profile of 20,173 genes.

RESULTS

One hundred seventy eight genes were up-regulated (>2-fold difference and DCD/LD > 1.5) and 120 down-regulated (<1/2-fold and LD/DCD > 1.5) in DCD kidneys. Expression of osteopontin (22.5 +/- 2.6-fold DCD vs 7.7 +/- 1.7 LD; P < .001), chemokines (CCL4 4.4 +/- 0.7 vs 2.5 +/- 0.3; P < .01), (CCL2 6.0 +/- 1.3 vs 2.8 +/- 0.5), CXCL1 (9.5 +/- 0.4 vs 2.0 +/- 0.2), and CXCL2 (16.7 +/- 5.3 vs 4.8 +/- 1.3; P < .05), adhesion molecule (ICAM-1 4.7 +/- 0.7 vs 2.5 +/- 0.4; P < .05), and heat shock proteins (HSPA1L 6.7 +/- 0.7 vs 1.6 +/- 0.3, HSPA1A 17.7 +/- 2.6 vs 2.4 +/- 0.5, HSPA1B 13.3 +/- 0.2 vs 3.0 +/- 0.7, HSPA5 6.7 +/- 0.8 vs 3.2 +/- 0.3, HSPB1 2.9 +/- 0.2 vs 1.0 +/- 0.1, and HSPH1 19.4 +/- 3.0 vs 5.9 +/- 1.1; P < .001) were up-regulated in the kidneys from DCD.

CONCLUSION

This report analyzed global gene expression using 1-hour biopsy samples from DCD kidneys. These results may provide new insight into the identification of novel target genes for the development of therapeutic approaches and for determining graft viability of kidneys from DCD.

Mechanistic pathways and biological roles for receptor-independent activators of G-protein signaling

Signal processing via heterotrimeric G-proteins in response to cell surface receptors is a central and much investigated aspect of how cells integrate cellular stimuli to produce coordinated biological responses. The system is a target of numerous therapeutic agents and plays an important role in adaptive processes of organs; aberrant processing of signals through these transducing systems is a component of various disease states. In addition to G-protein coupled receptor (GPCR)-mediated activation of G-protein signaling, nature has evolved creative ways to manipulate and utilize the Galphabetagamma heterotrimer or Galpha and Gbetagamma subunits independent of the cell surface receptor stimuli. In such situations, the G-protein subunits (Galpha and Gbetagamma) may actually be complexed with alternative binding partners independent of the typical heterotrimeric Galphabetagamma. Such regulatory accessory proteins include the family of regulator of G-protein signaling (RGS) proteins that accelerate the GTPase activity of Galpha and various entities that influence nucleotide binding properties and/or subunit interaction. The latter group of proteins includes receptor-independent activators of G-protein signaling (AGS) proteins that play surprising roles in signal processing. This review provides an overview of our current knowledge regarding AGS proteins. AGS proteins are indicative of a growing number of accessory proteins that influence signal propagation, facilitate cross talk between various types of signaling pathways, and provide a platform for diverse functions of both the heterotrimeric Galphabetagamma and the individual Galpha and Gbetagamma subunits.

Allogeneic activation is attenuated in a model of mouse lung perfused with magnesium-deficient blood

Hypomagnesemia, which is frequently observed in patients treated with calcineurin inhibitors to prevent rejection after allogeneic transplantation, has been associated with a faster rate of decline in allograft function. The effect of hypomagnesemia on lung allograft has not been reported yet. In our model of isolated mouse lung, we have evaluated the early effects of allogeneic lung perfusion with blood from magnesium (Mg)-deficient mice for 3 h on lung activation and remodelling, compared to isogeneic perfusion. Hypomagnesemia (0.21+/-0.07 mmol Mg(2+)/l) was observed in blood from Mg-deficient mice, but no inflammatory pattern. The mRNA level of the intercellular adhesion molecule (ICAM)-1, but neither of the vascular cell adhesion molecule (VCAM)-1, nor of the cytokines tumor necrosis factor (TNF)alpha and interleukin (IL)-2, was enhanced (p<0.05). Although caspase-3 mRNA was transiently enhanced, no apoptotic cells were evidenced in lung tissues even after 3 h. Using cDNA array, we found that the genes encoding RANKL, RANK, TNFR2, NFATX, IL-1R2, IL-6R gp130, SOCS3, PDGFRB, P63, CSF3R, CXCL1, CXCL5, CX3CL1, CSF1, which are involved in inflammation and apoptosis regulation, were markedly up-regulated in allogeneic conditions. Our results support a limited allogeneic activation and an early stage of the inflammatory process in lung, at the time of inflammatory cell recruitment without lung tissue remodelling, as a result of hypomagnesemia. These findings suggest that cyclosporine-related hypomagnesemia, observed in most of the transplanted patients, does not constitute an additional risk for lung allograft outcome.

Transcriptomic changes in developing kidney exposed to chronic hypoxia

cDNA arrays compared gene expression in kidneys of neonatal mice subjected to 1, 2, and 4 weeks of chronic constant (CCH) or intermittent (CIH) hypoxia with normoxic littermates. Five to twenty percent of genes were regulated in each condition, with greater changes in CCH. Up-regulation of 42% of the solute carriers after 1 week of CCH suggests a strong activation of pH controlling pathways. Significant reduction in expression change of genes important in growth, development, and aging as a function of time indicates reduced maturation rate in CIH and CCH treatments. Regulated genes showed gender dependence in CCH, being higher in females than males at 1 week and higher in males than females thereafter. Transcriptional control was enhanced in CCH but not in CIH. Thus, CCH and CIH both alter gene expression and retard maturation with the more profound changes occurring in CCH than in CIH.