Radicicol, a heat shock protein 90 inhibitor, reduces glomerular filtration rate

Decoding the anti-hypertensive mechanism of α-mangostin based on network pharmacology, molecular docking and experimental validation

BACKGROUND

Hypertension is a leading risk factor for disability and deaths worldwide. Evidence indicates that alpha-mangostin(α-MG) can reduce blood pressure and improve target organ damage. Nonetheless, its pharmacological targets and potential mechanisms of action remain inadequately elucidated.

METHOD

We used SwissTargetPrediction to identify α-MG's drug targets and DisGeNET, GeneCards, CTD, and GEO databases for hypertension-related targets, and then determined antihypertensive therapeutic targets of α-MG by intersecting these targets. GO functional enrichment analysis, KEGG pathway analysis, and disease association analysis were conducted using the DAVID database and R package "clusterprofile", visualized with Cytoscape software. The binding affinity of α-MG to identified targets was confirmed through molecular docking using Autodock Vina v.1.2.2 software. The impact of α-MG on target genes was validated using an Angiotensin II-induced hypertensive mouse model and RT-qPCR.

RESULTS

A total of 51 potential antihypertensive therapeutic targets for α-MG were identified by intersecting 109 drug targets with 821 disease targets. Furthermore, 10 cellular component terms, 10 disease terms, and the top 20 enriched biological processes, molecular functions, and KEGG pathways related to α-MG's antihypertensive effects were documented. Molecular docking studies indicated a strong binding affinity of α-MG with the HSP90AA1 domain. In Ang II-induced hypertensive mice aorta, treatment with α-MG effectively reversed the aberrant mRNA expression of TNF, HSP90AA1, NFKB1, PPARG, SIRT1, PTGS2, and RELA.

CONCLUSION

Our analyses showed that TNF, HSP90AA1, NFKB1, PPARG, SIRT1, PTGS2, and RELA might be α-MG's potential therapeutic targets for hypertension, laying groundwork for further investigation into its pharmacological mechanisms and clinical uses.

The mitochondrial redistribution of ENOS is regulated by AKT1 and dimer status

Previously, we have shown that endothelial nitric-oxide synthase (eNOS) dimer levels directly correlate with the interaction of eNOS with hsp90 (heat shock protein 90). Further, the disruption of eNOS dimerization correlates with its redistribution to the mitochondria. However, the causal link between these events has yet to be investigated and was the focus of this study. Our data demonstrates that simvastatin, which decreases the mitochondrial redistribution of eNOS, increased eNOS-hsp90 interactions and enhanced eNOS dimerization in cultured pulmonary arterial endothelial cells (PAEC) from a lamb model of pulmonary hypertension (PH). Our data also show that the dimerization of a monomeric fraction of human recombinant eNOS was stimulated in the presence of hsp90 and ATP. The over-expression of a dominant negative mutant of hsp90 (DNHsp90) decreased eNOS dimer levels and enhanced its mitochondrial redistribution. We also found that the peroxynitrite donor3-morpholinosydnonimine (SIN-1) increased the mitochondrial redistribution of eNOS in PAEC and this was again associated with decreased eNOS dimer levels. Our data also show in COS-7 cells, the SIN-1 mediated mitochondrial redistribution of wildtype eNOS (WT-eNOS) is significantly higher than a dimer stable eNOS mutant protein (C94R/C99R-eNOS). Conversely, the mitochondrial redistribution of a monomeric eNOS mutant protein (C96A-eNOS) was enhanced. Finally, we linked the SIN-1-mediated mitochondrial redistribution of eNOS to the Akt1-mediated phosphorylation of eNOS at Serine(S)617 and showed that the accessibility of this residue to phosphorylation is regulated by dimerization status. Thus, our data reveal a novel mechanism of pulmonary endothelial dysfunction mediated by mitochondrial redistribution of eNOS, regulated by dimerization status and the phosphorylation of S617.

Mitochondrial Impairment: A Link for Inflammatory Responses Activation in the Cardiorenal Syndrome Type 4

Cardiorenal syndrome type 4 (CRS type 4) occurs when chronic kidney disease (CKD) leads to cardiovascular damage, resulting in high morbidity and mortality rates. Mitochondria, vital organelles responsible for essential cellular functions, can become dysfunctional in CKD. This dysfunction can trigger inflammatory responses in distant organs by releasing Damage-associated molecular patterns (DAMPs). These DAMPs are recognized by immune receptors within cells, including Toll-like receptors (TLR) like TLR2, TLR4, and TLR9, the nucleotide-binding domain, leucine-rich-containing family pyrin domain-containing-3 (NLRP3) inflammasome, and the cyclic guanosine monophosphate (cGMP)-adenosine monophosphate (AMP) synthase (cGAS)-stimulator of interferon genes (cGAS-STING) pathway. Activation of these immune receptors leads to the increased expression of cytokines and chemokines. Excessive chemokine stimulation results in the recruitment of inflammatory cells into tissues, causing chronic damage. Experimental studies have demonstrated that chemokines are upregulated in the heart during CKD, contributing to CRS type 4. Conversely, chemokine inhibitors have been shown to reduce chronic inflammation and prevent cardiorenal impairment. However, the molecular connection between mitochondrial DAMPs and inflammatory pathways responsible for chemokine overactivation in CRS type 4 has not been explored. In this review, we delve into mechanistic insights and discuss how various mitochondrial DAMPs released by the kidney during CKD can activate TLRs, NLRP3, and cGAS-STING immune pathways in the heart. This activation leads to the upregulation of chemokines, ultimately culminating in the establishment of CRS type 4. Furthermore, we propose using chemokine inhibitors as potential strategies for preventing CRS type 4.

Effects of modified Huangqi Chifeng decoction on the IL-17 signaling pathway in an IgA nephropathy rat model

ETHNOPHARMACOLOGICAL RELEVANCE

Immunoglobulin A nephropathy (IgAN) is an immune-related primary glomerular disease prevalent worldwide, with complicated clinical manifestations and an unclear pathogenesis. IgAN is the main cause of chronic renal failure and places a significant burden on patients and society. The modified Huangqi Chifeng decoction (MHCD) is an effective prescription for the clinical treatment of IgAN while its specific mechanism remains to be further elucidated.

AIM OF THE STUDY

Based on the findings of previous network pharmacology-related method-based studies, this study aimed to further explore the mechanism of action of MHCD for IgAN treatment.

MATERIALS AND METHODS

IgAN rat model was established by bovine serum protein + carbon tetrachloride + lipopolysaccharide. After successful modeling, the rats in the original model group were divided into 5 group: model group, telmisartan group, and MHCD high-, medium- and low-dose groups by random number table (n = 10 respectively). The corresponding drugs were applied for 8 weeks, and the experiment lasted for 21 weeks. At the end of the experiment, 24h urine protein quantification, serum biochemistry and IL-6 and IL-17A levels were measured. The pathological changes of kidney were observed by light microscope, immunofluorescence microscope and the changes of glomerular ultrastructure were observed by transmission electron microscope. The expression levels of IL-17 signaling pathway related proteins (HSP90, MMP9, NF-κB P65 and p-NF-κB P65) were detected by Western Blot and immunohistochemistry.

RESULT

Telmisartan and MHCD treatment can reduce the 24h urinary protein level and improved blood stasis states of IgAN rats, alleviate the renal pathological injury, decrease the serum levels of IL-6, IL-17A and the expression levels of HSP90, MMP9 and p-NF-κB P65 related proteins in IL-17 signaling pathway.

CONCLUSION

MHCD can down-regulate the expression of IL-17 signaling pathway-related factors in IgAN model rats, improve the state of blood stasis, and alleviate the pathological damage of kidney in rats.

The Link Between Heat Shock Proteins, Renin-Angiotensin System, and the Coagulation Cascade in the Pathogenesis of the Coronavirus-19 Disease

INTRODUCTION

Understanding the pathogenesis of COVID-19 is integral for its successful treatment.

METHODS

Available literature on the relationship between COVID-19, heat shock proteins (HSP), and the renin-angiotensin-aldosterone (RAAS) system were searched and used to hypothesize how HSP can be targeted in COVID-19.

RESULTS

During SARS-CoV-2 cellular entry, the ACE-2 receptor is downregulated. This leads to the augmentation of angiotensin-2/AT1 receptor axis along with attenuation of the ACE-2/angiotensin_1-7/Mas axis. Heat shock proteins are key stabilizing molecules in various pathways.In the heart and vessels, HSP-90 and HSP-60 can facilitate angiotensin-2-mediated myocardial injury and endothelial cell activation. HSP-60-TLR4/CD14 complex formation stabilizes IκB-kinase (IKK) potentiating NF-κB activation. HSPs in lungs and kidneys have antioxidant, vasodilatory, and anti-inflammatory actions and may be protective against the effects of RAAS. Stress-induced HSP-70 has a role in complement-mediated microvascular injury such as has been demonstrated in COVID-19. SARS-CoV-2 can induce autophagy via Beclin-1 and ER (endoplasmic reticular) stress via BIP. These two can be potential targets in the HSP environment.

CONCLUSION

Various HSP molecules can modulate the effects of the renin-angiotensin-aldosterone (RAAS) system and thus may have a potential role in the pathogenesis of COVID-19.

Heat Shock Proteins: Connectors between Heart and Kidney

Over the development of eukaryotic cells, intrinsic mechanisms have been developed in order to provide the ability to defend against aggressive agents. In this sense, a group of proteins plays a crucial role in controlling the production of several proteins, guaranteeing cell survival. The heat shock proteins (HSPs), are a family of proteins that have been linked to different cellular functions, being activated under conditions of cellular stress, not only imposed by thermal variation but also toxins, radiation, infectious agents, hypoxia, etc. Regarding pathological situations as seen in cardiorenal syndrome (CRS), HSPs have been shown to be important mediators involved in the control of gene transcription and intracellular signaling, in addition to be an important connector with the immune system. CRS is classified as acute or chronic and according to the first organ to suffer the injury, which can be the heart (CRS type 1 and type 2), kidneys (CRS type 3 and 4) or both (CRS type 5). In all types of CRS, the immune system, redox balance, mitochondrial dysfunction, and tissue remodeling have been the subject of numerous studies in the literature in order to elucidate mechanisms and propose new therapeutic strategies. In this sense, HSPs have been targeted by researchers as important connectors between kidney and heart. Thus, the present review has a focus to present the state of the art regarding the role of HSPs in the pathophysiology of cardiac and renal alterations, as well their role in the kidney–heart axis.

Epigenome-wide association study of kidney function identifies trans-ethnic and ethnic-specific loci

BACKGROUND

DNA methylation (DNAm) is associated with gene regulation and estimated glomerular filtration rate (eGFR), a measure of kidney function. Decreased eGFR is more common among US Hispanics and African Americans. The causes for this are poorly understood. We aimed to identify trans-ethnic and ethnic-specific differentially methylated positions (DMPs) associated with eGFR using an agnostic, genome-wide approach.

METHODS

The study included up to 5428 participants from multi-ethnic studies for discovery and 8109 participants for replication. We tested the associations between whole blood DNAm and eGFR using beta values from Illumina 450K or EPIC arrays. Ethnicity-stratified analyses were performed using linear mixed models adjusting for age, sex, smoking, and study-specific and technical variables. Summary results were meta-analyzed within and across ethnicities. Findings were assessed using integrative epigenomics methods and pathway analyses.

RESULTS

We identified 93 DMPs associated with eGFR at an FDR of 0.05 and replicated 13 and 1 DMPs across independent samples in trans-ethnic and African American meta-analyses, respectively. The study also validated 6 previously published DMPs. Identified DMPs showed significant overlap enrichment with DNase I hypersensitive sites in kidney tissue, sites associated with the expression of proximal genes, and transcription factor motifs and pathways associated with kidney tissue and kidney development.

CONCLUSIONS

We uncovered trans-ethnic and ethnic-specific DMPs associated with eGFR, including DMPs enriched in regulatory elements in kidney tissue and pathways related to kidney development. These findings shed light on epigenetic mechanisms associated with kidney function, bridging the gap between population-specific eGFR-associated DNAm and tissue-specific regulatory context.

Geraniin is a diuretic by inhibiting the Na+-K+-2Cl- cotransporter NKCC2

Geranium seemannii Peyr is a perennial plant endemic to central Mexico that has been widely used for its diuretic effect, but the responsible compound of this effect is unknown as well as the mechanism by which the diuretic effect is achieved. Geraniin is one of the compounds isolated from this kind of geranium. This study was designed to determinate whether geraniin possesses diuretic activity and to elucidate the mechanism of action. Geraniin was extracted and purified from Geranium seemannii Peyr. Male Wistar rats were divided into four groups: 1) Control, 2) 75 mg/kg of geraniin, 3) 20 mg/kg of furosemide, and 4) 10 mg/kg of hydrochlorothiazide. Each treatment was administered by gavage every 24 h for 7 days. The urinary excretion of electrolytes and the fractional excretion of sodium (FENa) were determined. To uncover the molecular target of geraniin, Xenopus laevis oocytes were microinjected with cRNAs encoding the Na⁺-Cl^- cotransporter (NCC) and the Na⁺-K⁺-2Cl^- cotransporter NKCC2 to functionally express these cotransporters. Geraniin significantly increased diuresis, natriuresis, and calciuresis to a similar extent as was observed in the furosemide-treated rats. Consistent with the furosemide-like effect, in X. laevis oocytes, geraniin significantly reduced the activity of NKCC2, with no effect on NCC activity. In contrast to furosemide, the effect of geraniin on NKCC2 was irreversible, apparently due to its inhibitory effect on heat shock protein 90. Our observations suggest that geraniin could have a potential role in the treatment of hypertension or edematous states.

Heat shock proteins and kidney disease: perspectives of HSP therapy

Heat shock proteins (HSPs) mediate a diverse range of cellular functions, prominently including folding and regulatory processes of cellular repair. A major property of these remarkable proteins, dependent on intracellular or extracellular location, is their capacity for immunoregulation that optimizes immune activity while avoiding hyperactivated inflammation. In this review, recent investigations are described, which examine roles of HSPs in protection of kidney tissue from various traumatic influences and demonstrate their potential for clinical management of nephritic disease. The HSP70 class is particularly attractive in this respect due to its multiple protective effects. The review also summarizes current understanding of HSP bioactivity in the pathophysiology of various kidney diseases, including acute kidney injury, diabetic nephropathy, chronic glomerulonephritis, and lupus nephritis-along with other promising strategies for their remediation, such as DNA vaccination.

Accessory proteins for heterotrimeric G-proteins in the kidney

Heterotrimeric G-proteins play a fundamentally important role in regulating signal transduction pathways in the kidney. Accessory proteins are being identified as direct binding partners for heterotrimeric G-protein α or βγ subunits to promote more diverse mechanisms by which G-protein signaling is controlled. In some instances, accessory proteins can modulate the signaling magnitude, localization, and duration following the activation of cell membrane-associated receptors. Alternatively, accessory proteins complexed with their G-protein α or βγ subunits can promote non-canonical models of signaling activity within the cell. In this review, we will highlight the expression profile, localization and functional importance of these newly identified accessory proteins to control the function of select G-protein subunits under normal and various disease conditions observed in the kidney.

Endothelial nitric oxide synthase dimerization is regulated by heat shock protein 90 rather than by phosphorylation

Endothelial nitric oxide synthase (eNOS) is a multifunctional enzyme with roles in diverse cellular processes including angiogenesis, tissue remodeling, and the maintenance of vascular tone. Monomeric and dimeric forms of eNOS exist in various tissues. The dimeric form of eNOS is considered the active form and the monomeric form is considered inactive. The activity of eNOS is also regulated by many other mechanisms, including amino acid phosphorylation and interactions with other proteins. However, the precise mechanisms regulating eNOS dimerization, phosphorylation, and activity remain incompletely characterized. We utilized purified eNOS and bovine aorta endothelial cells (BAECs) to investigate the mechanisms regulating eNOS degradation. Both eNOS monomer and dimer existed in purified bovine eNOS. Incubation of purified bovine eNOS with protein phosphatase 2A (PP2A) resulted in dephosphorylation at Serine 1179 (Ser1179) in both dimer and monomer and decrease in eNOS activity. However, the eNOS dimer∶monomer ratio was unchanged. Similarly, protein phosphatase 1 (PP1) induced dephosphorylation of eNOS at Threonine 497 (Thr497), without altering the eNOS dimer∶monomer ratio. Different from purified eNOS, in cultured BAECs eNOS existed predominantly as dimers. However, eNOS monomers accumulated following treatment with the proteasome inhibitor lactacystin. Additionally, treatment of BAECs with vascular endothelial growth factor (VEGF) resulted in phosphorylation of Ser1179 in eNOS dimers without altering the phosphorylation status of Thr497 in either form. Inhibition of heat shock protein 90 (Hsp90) or Hsp90 silencing destabilized eNOS dimers and was accompanied by dephosphorylation both of Ser1179 and Thr497. In conclusion, our study demonstrates that eNOS monomers, but not eNOS dimers, are degraded by ubiquitination. Additionally, the dimeric eNOS structure is the predominant condition for eNOS amino acid modification and activity regulation. Finally, destabilization of eNOS dimers not only results in eNOS degradation, but also causes changes in eNOS amino acid modifications that further affect eNOS activity.

Intra-renal transfection of heat shock protein 90 alpha or beta (Hsp90α or Hsp90β) protects against ischemia/reperfusion injury

BACKGROUND

We previously reported that radicicol (Hsp90 inhibitor) induced a reduction in the renal blood flow and glomerular filtration rate, in part due to a reduction in urinary NO2/NO3 excretion, suggesting that Hsp90 regulates renal vascular tone in physiological conditions. However, there is a lack of information concerning Hsp90α or Hsp90β role on eNOS activity and their association with acute kidney injury (AKI) characterized by an inadequate NO production. This study evaluated the effects of Hsp90α or Hsp90β intra-renal transfection under ischemia/reperfusion (IR) injury.

METHODS

Uninephrectomized (Nx) rats were intra-renally transfected through injections with Hsp90α or Hsp90β cloned into pcDNA3.1(+) or empty vector (EV) at 48 h before inducing IR, as indicated in the following groups: (i) Nx+sham, (ii) Nx+IR, (iii) Nx+IR+EV, (iv) Nx+IR+Hsp90α and (v) Nx+IR+Hsp90β. After 24 h, physiological, histopathological, biochemical and molecular studies were performed.

RESULTS

IR-induced renal dysfunction, structural injury, tubular proliferation, the elevation of urinary Hsp72 and the reduction of urinary NO2/NO3 excretion. These alterations were associated with reduced eNOS-Hsp90 coupling and changes in the eNOS phosphorylation state mediated through a reduction in PKCα and increased Rho kinase expression. In contrast, intra-renal transfection of Hsp90α or Hsp90β prevented IR injury that was associated with the restoration of eNOS-Hsp90 coupling, eNOS activating phosphorylation and PKCα and Rho kinase levels.

CONCLUSIONS

Here we showed that eNOS-Hsp90 uncoupling plays a critical role in promoting NO reduction during IR. This effect was effectively reversed through Hsp90α or Hsp90β intra-renal transfection, suggesting their implication in regulating NO/eNOS pathway and the renal vascular tone.

Mineralocorticoid receptor blockade reduced oxidative stress in renal transplant recipients: a double-blind, randomized pilot study

BACKGROUND

Previous experimental studies from our laboratory have demonstrated that aldosterone plays a central role in renal ischemic processes. This study was designed to evaluate the effect of mineralocorticoid receptor blockade in renal transplant recipients from living donors.

METHODS

20 adult kidney transplant recipients from living donors were included in a double-blind, randomized, placebo-controlled clinical pilot study that compared spironolactone and placebo. Placebo or spironolactone (25 mg) was administered 1 day before and 3 days posttransplantation. Renal function and urinary kidney injury molecule-1, interleukin-18, and heat shock protein 72 as well as urinary hydrogen peroxide (H2O2) levels were quantified.

RESULTS

No significant differences were seen between the groups studied regarding age, gender, indication for kidney transplantation, residual renal function, renal replacement therapy, or warm and cold ischemia periods. In contrast, spironolactone administration significantly reduced the oxidative stress assessed by the urinary H2O2 excretion, in spite of no differences in renal function or reduction in tubular injury biomarkers.

CONCLUSIONS

The findings of this exploratory study strongly suggest that aldosterone promotes oxidative stress and that the administration of spironolactone reduces the production of urinary H2O2 as a result of lesser formation of surrogate reactive oxygen species secondary to the ischemia-reperfusion phenomenon.

Discovery and validation of small-molecule heat-shock protein 90 inhibitors through multimodality molecular imaging in living subjects

Up-regulation of the folding machinery of the heat-shock protein 90 (Hsp90) chaperone protein is crucial for cancer progression. The two Hsp90 isoforms (α and β) play different roles in response to chemotherapy. To identify isoform-selective inhibitors of Hsp90(α/β)/cochaperone p23 interactions, we developed a dual-luciferase (Renilla and Firefly) reporter system for high-throughput screening (HTS) and monitoring the efficacy of Hsp90 inhibitors in cell culture and live mice. HTS of a 30,176 small-molecule chemical library in cell culture identified a compound, N-(5-methylisoxazol-3-yl)-2-[4-(thiophen-2-yl)-6-(trifluoromethyl)pyrimidin-2-ylthio]acetamide (CP9), that binds to Hsp90(α/β) and displays characteristics of Hsp90 inhibitors, i.e., degradation of Hsp90 client proteins and inhibition of cell proliferation, glucose metabolism, and thymidine kinase activity, in multiple cancer cell lines. The efficacy of CP9 in disrupting Hsp90(α/β)/p23 interactions and cell proliferation in tumor xenografts was evaluated by non-invasive, repetitive Renilla luciferase and Firefly luciferase imaging, respectively. At 38 h posttreatment (80 mg/kg × 3, i.p.), CP9 led to selective disruption of Hsp90α/p23 as compared with Hsp90β/p23 interactions. Small-animal PET/CT in the same cohort of mice showed that CP9 treatment (43 h) led to a 40% decrease in (18)F-fluorodeoxyglucose uptake in tumors relative to carrier control-treated mice. However, CP9 did not lead to significant degradation of Hsp90 client proteins in tumors. We performed a structural activity relationship study with 62 analogs of CP9 and identified A17 as the lead compound that outperformed CP9 in inhibiting Hsp90(α/β)/p23 interactions in cell culture. Our efforts demonstrated the power of coupling of HTS with multimodality molecular imaging and led to identification of Hsp90 inhibitors.

Pathophysiology of acute kidney injury

Acute kidney injury (AKI) is the leading cause of nephrology consultation and is associated with high mortality rates. The primary causes of AKI include ischemia, hypoxia, or nephrotoxicity. An underlying feature is a rapid decline in glomerular filtration rate (GFR) usually associated with decreases in renal blood flow. Inflammation represents an important additional component of AKI leading to the extension phase of injury, which may be associated with insensitivity to vasodilator therapy. It is suggested that targeting the extension phase represents an area potential of treatment with the greatest possible impact. The underlying basis of renal injury appears to be impaired energetics of the highly metabolically active nephron segments (i.e., proximal tubules and thick ascending limb) in the renal outer medulla, which can trigger conversion from transient hypoxia to intrinsic renal failure. Injury to kidney cells can be lethal or sublethal. Sublethal injury represents an important component in AKI, as it may profoundly influence GFR and renal blood flow. The nature of the recovery response is mediated by the degree to which sublethal cells can restore normal function and promote regeneration. The successful recovery from AKI depends on the degree to which these repair processes ensue and these may be compromised in elderly or chronic kidney disease (CKD) patients. Recent data suggest that AKI represents a potential link to CKD in surviving patients. Finally, earlier diagnosis of AKI represents an important area in treating patients with AKI that has spawned increased awareness of the potential that biomarkers of AKI may play in the future.

Hsp90 inhibition: elimination of shock and stress

The 90 kDa heat shock proteins (Hsp90) represent a class of molecular chaperones responsible for the maturation and stabilization of many oncogenic proteins. Disrupting the ability of ATP to bind and facilitate the operation of Hsp90 has emerged as a promising approach toward cancer chemotherapeutic development. While numerous Hsp90 inhibitory scaffolds have been identified, progress through the clinic has revealed many obstacles that should be addressed in future analogue development. Recent reports of the complications, pitfalls, and downstream effects associated with Hsp90 inhibition are discussed herein, in hopes of providing a reference that can be used to guide the future design of Hsp90 inhibitory scaffolds.

Polymerized type I collagen reduces chronic cyclosporine nephrotoxicity

BACKGROUND

Polymerized type I collagen (P-collagen) has been successfully used to reduce human hypertrophic scars due to its anti-fibrotic and anti-inflammatory properties. We therefore carried out a study to determine if P-collagen reduces functional and structural injury in chronic cyclosporine [cyclosporine A (CsA)] nephropathy.

METHODS

Four groups of six male Wistar rats fed with a low sodium diet were treated with vehicle, P-collagen (0.8 mg/day, i.p.), CsA (15 mg/kg) or CsA + P-collagen for 15 days. Mean arterial pressure, renal blood flow and glomerular filtration rate were measured in all groups. Structural injury such as arteriolopathy, tubulo-interstitial fibrosis (TI-fibrosis) and positive apoptotic cells were quantified. The mRNA expression levels of transforming growth factor-beta (TGF-beta), kidney injury molecule (Kim-1), alpha-smooth muscle actin (alpha-SMA), glutathione peroxidase, catalase and Cu/Zn superoxide dismutase (SOD) as well as MnSOD were assessed. Antioxidant enzyme activity, renal lipoperoxidation and urinary excretion of oxygen peroxide (UH(2)O(2)V) were determined.

RESULTS

Cyclosporine produced renal dysfunction and induced the development of arteriolopathy, TI-fibrosis and tubular apoptosis. These alterations were associated with increases in TGF-beta, Kim-1 and alpha-SMA mRNA levels as well as with a significant increase of oxidative stress and a reduction of SOD activity. P-Collagen partially ameliorated CsA-induced renal dysfunction and structural injury and prevented both tubular apoptosis and increased oxidative stress. This renoprotective effect was found to be associated with a reduction of TGF-beta, Kim-1 and alpha-SMA mRNA levels.

CONCLUSIONS

This study has therefore demonstrated that P-collagen appears to have anti-fibrotic and anti-apoptotic properties and highlights the possibility that the compound might be useful in a strategy to reduce chronic CsA nephrotoxicity.