Response of Encapsulated Rat Pancreatic Islets to Hypoxia

Hypoxia contributes to encapsulated pancreatic islet graft failure. To gain insight into the mechanisms that lead to hypoxia-induced graft failure, encapsulated islet function, vitality, and cell replication were assessed after 2 and 5 days of hypoxic (1% O₂) and normoxic (20% O₂) culture. The mRNA expression levels of Bcl-2, Bax, inducible nitric oxide synthase (iNOS), and monocyte chemoattractant protein 1 (MCP-1) were assessed, as well as the amount of nitrite and MCP-1 in the culture medium. Hypoxia was associated with loss of encapsulated islet function and vitality, but not with an increase in islet cell replication. Loss of vitality was due to necrosis, and only modestly due to apoptosis. Hypoxia was not associated with changes in the Bcl-2/Bax mRNA ratio, but it did increase the expression of iNOS and MCP-1 mRNA. The increased mRNA levels were, however, not associated with elevated concentrations of nitrite nor with elevated levels of MCP-1 protein. The increased iNOS mRNA levels imply a role for NO in the completion of cell death by hypoxia. The increased MCP-1 mRNA levels suggest that encapsulated islets in vivo contribute to their own graft failure by attracting cytokine-producing macrophages. The discrepancy between iNOS mRNA and nitrite is explained by the longer half-life of NO during hypoxia. MCP-1 protein levels are underestimated as a consequence of the lower number of vital cells in combination with a higher proteolytic activity due to necrosis. Thus, strategies to eliminate hypoxia may not only improve islet function and vitality, but may also reduce the attraction of macrophages by encapsulated islets.

Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in an STI population: performances of the Presto CT-NG assay, the Lightmix Kit 480 HT CT/NG and the COBAS Amplicor with urine specimens and urethral/cervicovaginal samples

OBJECTIVES

This study assessed the performances of the Presto CT-NG assay, the Lightmix Kit 480 HT CT/NG and the COBAS Amplicor for Chlamydia trachomatis and Neisseria gonorrhoeae detection.

DESIGN

A cross-sectional study design.

SETTING

Izore, Centre for Diagnosing Infectious Diseases in Friesland, the Netherlands, tested samples sent from regional sexually transmitted infection (STI) outpatient clinics and regional hospitals from the province Friesland, the Netherlands.

PARTICIPANTS

Samples were collected from 292 men and 835 women. These samples included 560 urine samples and 567 urethral/cervicovaginal samples.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure is C trachomatis infection. No secondary outcome measures are available.

RESULTS

The sensitivity, specificity, positive predicative value (PPV) and negative predictive value (NPV) for C trachomatis detection in urine samples using the Presto CT-NG assay were 100%, 99.8%, 98.1% and 100%, respectively; for the Lightmix Kit 480 HT CT/NG: 94.2%, 99.8%, 96.1% and 99.4%, respectively; for the COBAS Amplicor: 92.3%, 99.6%, 96% and 99.2%, respectively. The sensitivity, specificity, PPV and NPV for C trachomatis detection in urethral/cervicovaginal swabs using the Presto CT-NG assay and the COBAS Amplicor were 100%, 99.8%, 97.7% and 100%, respectively; for the Lightmix Kit 480 HT CT/NG: 100%, 99.6%, 97.7% and 100%, respectively. Calculations for N gonorrhoeae could not be made due to a low prevalence.

CONCLUSIONS

All three assays had a high sensitivity, specificity, PPV and NPV for C trachomatis, with best performance for the Presto CT-NG assay.

Kidney injury molecule-1 is an early noninvasive indicator for donor brain death-induced injury prior to kidney transplantation

With more marginal deceased donors affecting graft viability, there is a need for specific parameters to assess kidney graft quality at the time of organ procurement in the deceased donor. Recently, kidney injury molecule-1 (Kim-1) was described as an early biomarker of renal proximal tubular damage. We assessed Kim-1 in a small animal brain death model as an early and noninvasive marker for donor-derived injury related to brain death and its sequelae, with subsequent confirmation in human donors. In rat kidney, real-time PCR revealed a 46-fold Kim-1 gene upregulation after 4 h of brain death. In situ hybridization showed proximal tubular Kim-1 localization, which was confirmed by immunohistochemistry. Also, Luminex assay showed a 6.6-fold Kim-1 rise in urine after 4 h of brain death. In human donors, 2.5-fold kidney injury molecule-1 (KIM-1) gene upregulation and 2-fold higher urine levels were found in donation after brain death (DBD) donors compared to living kidney donors. Multiple regression analysis showed that urinary KIM-1 at brain death diagnosis was a positive predictor of recipient serum creatinine, 14 days (p < 0.001) and 1 year (p < 0.05) after kidney transplantation. In conclusion, we think that Kim-1 is a promising novel marker for the early, organ specific and noninvasive detection of brain death-induced donor kidney damage.

Signal transduction pathways involved in brain death-induced renal injury

Kidneys derived from brain death organ donors show an inferior survival when compared to kidneys derived from living donors. Brain death is known to induce organ injury by evoking an inflammatory response in the donor. Neuronal injury triggers an inflammatory response in the brain, leading to endothelial dysfunction and the release of cytokines in the circulation. Serum levels of interleukin-6, -8, -10, and monocyte chemoattractant protein-1 (MCP-1) are increased after brain death. Binding with cytokine-receptors in kidneys stimulates activation of nuclear factor-kappa B (NF-kappaB), selectins, adhesion molecules and production of chemokines leading to cellular influx. Mitogen-activated protein kinases (MAP-kinases) mediate inflammatory responses and together with NF-kappaB they seem to play an important role in brain death induced renal injury. Altering the activation state of MAP-kinases could be a promising drug target for early intervention to reduce cerebral injury related donor kidney damage and improve outcome after transplantation.

Time-dependent changes in donor brain death related processes

Donor brain death (BD) affects kidney function and survival after transplantation. Studies on brain dead kidney donors indicate that, besides inflammation and coagulation, cytoprotective gene expression is activated as well. Here, we evaluated in a time-course experiment progression of these renal BD-related processes. Animals were sacrificed 0.5, 1, 2 or 4 h after BD and compared to sham-operated controls. Proinflammatory genes (E-selectin, MCP-1, II-6) were massively up-regulated (p < 0.05) already 0.5 h after BD. Inducers of proinflammatory gene expression were either activated (NF-kappaB) or induced in expression (Egr-1) after 0.5 h of BD. Increased numbers of infiltrating granulocytes were seen in the interstitium from 0.5 h on. Also, expression of protective genes HO-1 and HSP70 were increased within 0.5 h. Remarkably, reactive oxygen species formation was detectable only in the later phase of BD. Among 14 measured serum cytokines, MCP-1 and KC-protein were significantly elevated from 0.5 h on. In conclusion, a fast induction of proinflammatory and stress-induced protective processes in brain dead donor kidneys was demonstrated, probably triggered by changes occurring during BD induction. Importantly, hypoxia appeared not to be one of the initial triggers, and early increased systemic levels of chemokines MCP-1 and KC may be regarded as the starting point for the inflammatory cascade in brain dead donor kidneys.

Effects of brain death on stress and inflammatory response in the human donor kidney

BACKGROUND

After kidney transplantation, a decreased graft survival is seen in grafts from brain dead donors compared to living donors, possibly related to a progressive inflammatory reaction in the graft. In this study, we focused on the effects of brain death on the inflammatory response (adhesion molecules, leukocyte infiltration, and gene expression) and stress-related heat shock proteins in the human kidney. Research outcomes and clinical donor parameters were linked to outcome data after transplantation.

METHODS

Human kidney biopsy specimens were obtained during organ retrieval from brain dead and living organ donor controls. On these specimens, immunohistochemistry and semiquantitative RT-PCR were performed. Regression analyses were performed connecting results to outcome data of kidney recipients.

RESULTS

In brain death, immunohistochemistry showed an increase of E-selectin and interstitial leukocyte invasion versus controls; RT-PCR showed an increase of gene expression of HO-1 and Hsp70. One and 3 years after transplantation, high ICAM and VCAM expression proved to have a negative effect on kidney function in brain dead and living kidneys, while HO-1 proved to have a strongly positive effect, but only in kidneys from living donors.

CONCLUSIONS

E-selectin expression and interstitial leukocyte accumulation in brain dead donor kidneys indicate an early phase inflammatory state prior to organ retrieval. Also, brain death causes a stress-related response resulting in upregulation of potentially protective heat shock proteins. The upregulation of HO-1 is beneficial in living donor kidneys, but might be inadequate in brain death.

Renal expression of heat shock proteins after brain death induction in rats

The majority of transplanted kidneys are derived from brain-dead patients. This nonphysiological state influences the hemodynamic and hormonal status of the donor. As a result, kidneys derived from brain-dead donors have inferior graft survival and increased graft function loss. Heat shock proteins (HSPs) are a family of stress-inducible proteins involved in maintaining cell homeostasis and regulating the immune system. We studied renal expression of the genes HO-1, HSP27, HSP40, and HSP70 after experimental brain death in rats. Brain death was induced in male F344 rats by slowly inflating a balloon catheter in the epidural space. Untreated rats were used as controls. Animals were humanely killed after 4 hours of brain death. Kidneys were analysed using RT-PCR, Western blotting, and immunohistochemistry. RT-PCR showed an increase in expression of genes coding for HO-1 (3.6-fold; P < .05) and HSP70 (2.7-fold; P < .05) after brain death. Western blotting also revealed an increase in HO-1 protein levels (4.6-fold; P < .001) but changes in HSP70 protein expression were not detected. Immunohistochemistry showed increments of HO-1 protein expression in the renal cortical tubules of brain-dead rats. HSP70 was predominantly increased in renal distal tubules of brain-dead rats treated for hypotension. No changes were observed in renal HSP27 and HSP40 expression after brain death. Renal stress caused by brain death induces expression of the cytoprotective genes HO-1 and HSP70, but not of HSP27 and HSP40. The up-regulation of these cytoprotective genes could be part of a recuperative mechanism induced by stress associated with brain death.

Rat islet isolation yield and function are donor strain dependent

Effective rat islet isolation is pertinent for successful islet transplantation and islet studies in vitro. To determine which rat strain yields the highest number of pure and functional islets, four commonly used rat strains were compared with regard to islet yield, islet purity and islet function. Secretory responses were assessed by stimulation with glucose, and by stimulation with glucose plus 3-isobutyl-1-methylxanthine (IBMX). We show that rat islet function and isolation yield are donor strain dependent. Albino Oxford (AO) rats donated twice as many islets than Wistar, Lewis and Sprague Dawley (SD) rats. Stimulation with glucose plus IBMX resulted in an average five-fold increase of the stimulation index of AO, Lewis, Wistar and SD rats compared to stimulation with glucose only. AO islets had improved secretory responses after a one-week culture period, but required the addition of IBMX to glucose to elicit a distinguished stimulated insulin secretion after 2 days of culture. Islets from SD rats showed inferior results with regard to purity immediately after isolation and with regard to function after short- and after long-time culture. Because Lewis islets possessed the highest secretory response to glucose (without IBMX) immediately after isolation, Lewis rats may be preferred as islet donors for immediate use. The addition of IBMX to glucose for in vitro functional testing is recommended because it elicits high insulin secretory responses of islets regardless of the rat strain. AO rats are preferred for culture experiments since the number of experimental animals is reduced two-fold compared to Lewis, Wistar and SD rats.

Response of encapsulated rat pancreatic islets to hypoxia

Hypoxia contributes to encapsulated pancreatic islet graft failure. To gain insight into the mechanisms that lead to hypoxia-induced graft failure, encapsulated islet function, vitality, and cell replication were assessed after 2 and 5 days of hypoxic (1% O2) and normoxic (20% O2) culture. The mRNA expression levels of Bcl-2, Bax, inducible nitric oxide synthase (iNOS), and monocyte chemoattractant protein 1 (MCP-1) were assessed, as well as the amount of nitrite and MCP-1 in the culture medium. Hypoxia was associated with loss of encapsulated islet function and vitality, but not with an increase in islet cell replication. Loss of vitality was due to necrosis, and only modestly due to apoptosis. Hypoxia was not associated with changes in the Bcl-2/Bax mRNA ratio, but it did increase the expression of iNOS and MCP-1 mRNA. The increased mRNA levels were, however, not associated with elevated concentrations of nitrite nor with elevated levels of MCP-1 protein. The increased iNOS mRNA levels imply a role for NO in the completion of cell death by hypoxia. The increased MCP-1 mRNA levels suggest that encapsulated islets in vivo contribute to their own graft failure by attracting cytokine-producing macrophages. The discrepancy between iNOS mRNA and nitrite is explained by the longer half-life of NO during hypoxia. MCP-1 protein levels are underestimated as a consequence of the lower number of vital cells in combination with a higher proteolytic activity due to necrosis. Thus, strategies to eliminate hypoxia may not only improve islet function and vitality, but may also reduce the attraction of macrophages by encapsulated islets.

Sulfur regulation of the sulfate transporter genes sutA and sutB in Penicillium chrysogenum

Penicillium chrysogenum uses sulfate as a source of sulfur for the biosynthesis of penicillin. Sulfate uptake and the mRNA levels of the sulfate transporter-encoding sutB and sutA genes are all reduced by high sulfate concentrations and are elevated by sulfate starvation. In a high-penicillin-yielding strain, sutB is effectively transcribed even in the presence of excess sulfate. This deregulation may facilitate the efficient incorporation of sulfur into cysteine and penicillin.

Sulfate transport in Penicillium chrysogenum: cloning and characterization of the sutA and sutB genes

In industrial fermentations, Penicillium chrysogenum uses sulfate as the source of sulfur for the biosynthesis of penicillin. By a PCR-based approach, two genes, sutA and sutB, whose encoded products belong to the SulP superfamily of sulfate permeases were isolated. Transformation of a sulfate uptake-negative sB3 mutant of Aspergillus nidulans with the sutB gene completely restored sulfate uptake activity. The sutA gene did not complement the A. nidulans sB3 mutation, even when expressed under control of the sutB promoter. Expression of both sutA and sutB in P. chrysogenum is induced by growth under sulfur starvation conditions. However, sutA is expressed to a much lower level than is sutB. Disruption of sutB resulted in a loss of sulfate uptake ability. Overall, the results show that SutB is the major sulfate permease involved in sulfate uptake by P. chrysogenum.

Positioning of nuclei in the secondary Mycelium of Schizophyllum commune in relation to differential gene expression

In this paper we propose a novel type of gene regulation in the MATA|l4 MATB|l4 heterokaryon of Schizophyllum commune by means of differential positioning of the nuclei. It was found that binucleate hyphae with juxtaposed nuclei secrete SC4 hydrophobin (abundant during fruit-body formation), while SC3 (abundant during aerial hyphae formation in both mono- and dikaryons) appeared to be absent. Certain growth conditions disrupted the binucleate state in that the compatible nuclei became separated at a considerable distance. Under these conditions SC4 was not secreted while SC3 was secreted to a high degree. Disruption of the binucleate state was earlier observed in developing aerial hyphae which secrete SC3. Apparently, when the nuclei are in close proximity the dikaryon-expressed genes are switched on by interaction of the products of the MATA and MATB mating-type genes, while SC3 is suppressed by interacting products of the MATB genes, as occurs in the common MATA heterokaryon (MATA= MATB|l4). Growth conditions that lead to disruption of the binucleate state apparently result in abolishment of interaction between the MATB mating-type genes. Under these conditions, dikaryon-specific mRNAs do not accumulate in the MATA|l4 MATB|l4 heterokaryon, while SC3 mRNA becomes highly abundant.

Homology-dependent silencing of the SC3 gene in Schizophyllum commune

After introduction of extra copies of the SC3 hydrophobin gene into a wild-type strain of Schizophyllum commune, gene silencing was observed acting on both endogenous and introduced SC3 genes in primary vegetative transformants. Nuclear run-on experiments indicated that silencing acted at the transcriptional level. Southern analysis revealed that cytosine methylation of genomic DNA occurred. Moreover, SC3 silencing was suppressed by exposure to 5-azacytidine during growth. After growth of SC3-suppressed colonies from homogenized mycelium or from colonies stored at 4 degrees, SC3 transcription was restored. However, after prolonged growth SC3 silencing was again observed. Introduction of a promoterless SC3 fragment into wild type gave less SC3 silencing.

Genetic regulation of emergent growth in Schizophyllum commune

After a period of juvenile growth, Schizophyllum commune starts to transcribe genes for a number of abundant cell-wall proteins that are excreted into the medium by submerged hyphae but become part of the cell wall in emergent structures. The dikaryon transcribes the genes SC1, SC3, SC4, and SC6 that encode hydrophobins and SC7 and SC14 that encode hydrophilic wall proteins of unknown function. Of these, only the SC3 gene is highly transcribed in the monokaryon. The SC3p hydrophobin forms an insoluble hydrophobic rodlet layer by interfacial self-assembly at the outer surface of aerial hyphae of both monokaryon and dikaryon. The SC4p hydrophobin forms an insoluble membrane separating the extracellular matrix surrounding dikaryotic hyphae of the plectenchyma from air cavities in the fruit bodies while the product of the SC7 gene is found within the extracellular matrix. However, these plectenchyma hyphae do not express the SC3 gene. Because SC3 activity is suppressed in a MATA = MATB≠ heterokaryon and a MATAx matBCon homokaryon, interaction between different B mating-type gene products appears responsible for suppression of SC3 in the hyphae that form the plectenchyma. On the other hand, in aerial hyphae of the MATA ≠ MATB≠ heterokaryon the binucleate state of the hyphae appears disrupted and this is accompanied by expression of SC3 only, as in the monokaryon. This suggests that regulation of specific genes by the products of different MATB genes only occurs when these genes are present in closely paired nuclei. Thus, spatial differences in gene expression during emergent growth in the MATA ≠ MATB≠ heterokaryon may occur by regulation of the nuclear distribution. Key words: Schizophyllum commune development, hydrophobins in development, mating-type genes in Schizophyllum, fruit-body development, emergent growth.