Donald C. Houghton

Cyclosporine-induced acute renal dysfunction in the rat: Evidence of arteriolar vasoconstriction with preservation of tubular function

Dose-related cyclosporine-induced renal dysfunction is the most frequent adverse effect noted with this exciting immunosuppressive drug. To investigate pathogenetic factors involved, we studied renal tubular function and afferent arteriolar morphology during severe experimental cyclosporine-induced reduction in glomerular filtration rate. Pair-fed male rats were given cyclosporine 50 mg/kg or olive oil vehicle alone by gavage for periods of 3-14 days. Glomerular filtration rate declined progressively, reaching a nadir of 0.18 +/- .05 ml/min/100 g vs. .86 +/- .03 ml/min/100 g in controls at 14 days (P less than 0.001). Despite the severe reduction in glomerular filtration rate there was no difference in fractional sodium excretion, fractional lithium excretion, enzymuria, or in vitro renal cortical slice uptake of tetraethylammonium in cyclosporine and vehicle-treated animals. Light microscopy showed vacuolar changes without evidence of tubular necrosis at 7 and 14 days in cyclosporine-treated rats. Progressive decline in the diameter of the afferent arteriole was noted by scanning electron microscopy. By day 14 the lumenal diameter of afferent arterioles from cyclosporine-treated animals was 8.9 +/- 0.4 micron vs. 13.5 +/- 0.4 micron in controls (P less than 0.05). We conclude that afferent arteriolar vasoconstriction rather than direct tubular injury is a major pathogenetic factor in experimental cyclosporine nephrotoxicity.

Modification of experimental nephrotoxicity with fish oil as the vehicle for cyclosporine.

Cyclosporine-associated renal dysfunction is well recognized. While renal vasoconstriction appears to be a major pathogenic factor, the precise mechanism responsible for the altered hemodynamics is unclear. To investigate whether alterations in renal eicosanoid metabolism could be involved, we substituted fish oil rich in eicosapentaenoic acid (EPA), an inhibitor of cyclooxy-genase metabolites, for the conventional olive oil cyclosporine vehicle. Male rats were pretreated with 1.0 cc fish oil or olive oil by gavage. After 14 days, cyclosporine (12.5 mg/cc vehicle) was added to the oil and animals received cyclosporine 50 mg/kg for an additional 14 days. Pair-fed control animals received fish oil or olive oil alone. Glomerular filtration rate (GFR) was severely reduced in the cyclosporine-in-olive-oil (CSA + OO) group (0.28±.05 ml/min/100 g) vs. olive oil (OO) controls (0.70±.04) (P<0.001). While GFR was reduced in the cyclosporine-in-fish oil group (CSA + FO) vs. fish oil (FO) controls (0.47±.07 vs. 0.74±.04), it was significantly higher than in the CSA + OO group (P<0.05). Trough whole-blood cyclosporine levels were not significantly different in the two groups. While CSA + OO appeared to elevate renal cortical content of thromboxane B2 (65.7±7.3 pg/mg tissue vs. 46.9±5.3 for OO), both the CSA + FO and FO groups had reduced levels (31.1±2.7 and 29.5±2.3, respectively). In addition, there was a striking reduction in proximal tubular vacuolar changes in the CSA ± FO vs. CSA + OO group. We conclude that the use of EPA-rich fish oil as the vehicle for cyclosporine results in improved renal function and morphology and is associated with depressed renal cortical levels of vasoconstrictor thromboxane B2.

Enhancement of FK506 nephrotoxicity by sodium depletion in an experimental rat model

FK506 can show efficacy in transplant rejection even after other immunosuppressive drugs have been ineffective. However, the lack of a suitable animal model has hindered the study of FK nephrotoxicity, which has been noted as a common adverse effect in human trials. In this paper, we report a model of chronic FK nephrotoxicity in which renal structure and function are worsened by sodium depletion. Pair-fed male Sprague-Dawley rats were given FK (6 mg/kg p.o.) or vehicle for 21 days on a low-salt or normal diet. There was no significant difference in body weight between FK and vehicle groups. The FK whole-blood trough levels (3-10 ng/ml) in rats are similar to those in FK treated transplant patients. In sodium-depleted rats, FK clearly decreased GFR (0.09 +/- 0.03 ml/min/100 g vs. 0.94 +/- 0.06 ml/min/100 g in the vehicle group, P < 0.01), urinary osmolarity (UOsm, P < 0.01) and plasma magnesium (P < 0.01) and increased plasma creatinine (Pcr, P < 0.01), fractional excretion of magnesium (P < 0.01), urine volume (P < 0.01), plasma renin activity (PRA, P < 0.05), and alanine aminopeptidase (AAP, P < 0.05) as compared with those in the vehicle group. Salt depletion significantly potentiated these functional changes as compared with those in the normal salt group (GFR, UOsm, Pcr, PRA, and AAP of the low salt group vs. those of the normal salt group, P < 0.05 by ANOVA). In the sodium-depleted rats, the main lesion in the rat kidneys was focal collapse and vacuolization in proximal tubules, but there was also significant interstitial fibrosis. In contrast, no injury was observed in the sodium-replete rat kidneys. In conclusion, an experimental model of FK nephrotoxicity in sodium-depleted rats has been developed that is characterized by reduced GFR and structural damage to the proximal tubule accompanied by interstitial fibrosis. Sodium depletion appears to potentiate these changes at blood levels similar to those achieved in patients receiving FK.

An abundance of IgG4+ plasma cells is not specific for IgG4-related tubulointerstitial nephritis

IgG4-related tubulointerstitial nephritis (IgG4-TIN), the renal parenchymal lesion of IgG4-related sclerosing disease, is characterized, among other things, by the presence of numerous IgG4-positive plasma cells (IgG4+PC) in the kidney infiltrate. The specificity of this finding for IgG4-TIN has not been addressed. To address this we examined 100 consecutive renal biopsy samples with active interstitial inflammation for the presence of IgG4+PC, and correlated the findings with principal diagnosis, the available clinical histories, and the findings in four biopsy samples of IgG4-TIN. Eleven of the survey biopsy samples contained an average of more than 10 IgG4+PC per × 200 field, including two with IgG4+PC in numbers comparable to those in two of the IgG4-related tubulointerstitial disease biopsy samples. The principal pathological diagnoses in the IgG4+PC-rich cases included anti-neutrophil cytoplasmic antibody-positive necrotizing glomerulonephritis (five cases), diabetic nephropathy (two cases), idiopathic interstitial nephritis (two cases), membranous glomerulonephritis (one case), and lupus nephritis (one case). There was no reason, based on histology or clinical history, to believe that any of these cases represented previously unsuspected IgG4-related tubulointerstitial disease. We conclude that the presence of numerous IgG4+PC is essential to, but not sufficient for, the diagnosis of IgG4-TIN.

HLA-DRB1*0102 is associated with TINU syndrome and bilateral, sudden-onset anterior uveitis but not with interstitial nephritis alone

Background Tubulointerstitial nephritis and uveitis (TINU) syndrome is a rare form of uveitis. Previously, the authors had demonstrated a strong association of human leukocyte antigen (HLA) DRB1*0102 with TINU. Here, the authors performed HLA analysis on subjects with isolated bilateral sudden-onset uveitis (as in the TINU subtype) or with isolated tubulointerstitial nephritis (TIN). Methods Patients with sudden onset, anterior, bilateral uveitis not fulfilling a diagnosis of TINU were identified. Pathology reports were reviewed to identify subjects with biopsy-proven TIN. Molecular typing of the HLA-DRB1 gene was performed by the Luminex technology-based sequence-specific oligonucleotide (SSO) hybridisation method (One Lambda, Canoga Park, California). HLA-DRB1 allele frequencies were compared with normal published controls (http://www.ncbi.nlm.nih.gov/projects/gv/mhc/ihwg.cgi dbMHC Europe cohort) and the published TINU cohort (n=18). Results The authors included 28 subjects with uveitis and 14 with TIN. There was a significantly higher frequency of DRB1*0102 in the isolated uveitis cohort versus in normal controls (10.7% vs 0.6%, respectively, p<0.0001; RR 14.3 (6.9–29.8)). None of the nephritis patients showed this HLA subtype. Another association with HLA-DRB1*08 was seen in the isolated uveitis cohort with an allele frequency of 10.7% versus 2.7% in normal controls (p=0.0019; RR 4.0 (1.8–9.0)). In contrast, the HLA-DRB1*08 was not different from controls in the TINU cohort (allele frequency 2.8%, p=not significant). Conclusion The incidence of HLA-DRB1*0102 is increased in sudden-onset bilateral anterior uveitis, as seen in patients with TINU. The same allele does not appear to occur in increased frequency in patients with isolated TIN. HLA DRB1*0102 might predispose to this subset of uveitis.

Diet-Induced Systemic Lupus Erythematosus (SLE) in Primates

Ten adult, female cynomolgus macaques were randomly assigned to two equal groups: (1) semipurified diet (SPD); and (2) SPD with 45% ground alfalfa seed (AS). Both groups were studied at monthly intervals after 5 mo on their respective diets. Control animals had a mean hematocrit (Hct) of 43 +/- 2%, negative antiglobulin (AG), antinuclear antibody (ANA) and LE cell tests. Mean values for C3 and C4 were 309 +/- 47 mg/dl and 35 +/- 7 mg/dl, respectively. Mean serum binding to radiolabeled double stranded deoxyribonucleic acid (dsDNA) was 1.9 +/- 0.2%. Three of five animals fed AS developed signs of an SLE-like illness characterized by AG-positive anemia (lowest Hct 30%), positive ANA (highest titer greater than 1:15, 360; rim pattern) and elevated anti-dsDNA binding (highest 96%) with variable degrees of hypocomplementemia. One animal had granular deposition of immunoglobulin and complement at the dermal-epidermal junction of clinically normal skin the presence of immune complex-induced glomerulonephritis.

Clinically relevant doses and blood levels produce experimental cyclosporine nephrotoxicity when combined with nitric oxide inhibition

Cyclosporine (CsA) administration and nitric oxide (NO) blockade promote similar chronic renal hemodynamic alterations in rats. We evaluated various clinical CsA doses under conditions of NO blockade using L-NAME (N-nitro L-arginine methyl ester). Groups of Sprague-Dawley rats kept on a normal salt (+NaCl) or low-salt (-NaCl) diet were given CsA 7.5 mg/kg, 2.5 mg/kg, or vehicle (VH) for 21 days. CsA or VH treatment was preceded by one week of L-NAME and continued for three weeks. Inulin clearance, CsA blood level, and weekly blood pressure change were assessed at 28 days. Marked CsA dose dependent reductions in GFR in -NaCl animals (P < 0.01 versus VH + L-NAME) and +NaCl animals (P < 0.05 versus VH + L-NAME, +NaCl) as well as blood pressure elevations (P < 0.01 versus VH + L-NAME at 28 days) occurred in groups concurrently treated with CsA and L-NAME. In addition, Impaired renal function and morphologic lesions in rats (CsA 2.5 mg/kg) receiving L-NAME or CsA alone demonstrated CsA blood levels within the therapeutic range of human renal transplant patients. VH groups treated with L-NAME alone produced blood pressure elevations but were spared of renal functional or morphological alterations. Primary renal morphologic lesions in CsA treated animals included proximal tubule collapse and vacuolization and, less frequently, interstitial edema and vacuolization of interstitial cells. Unique to rats treated simultaneously with CsA and L-NAME were vascular abnormalities consisting of endothelial and arteriolar medial hyperplasia and occasional acute medial necrosis. In conclusion, acute CsA nephrotoxicity can be enhanced by simultaneous NO blockade, suggesting NO has a protective effect in CsA-induced nephropathy. These results can be achieved with a drug exposure profile that correlates with clinical therapy.

IgG4 Immunostaining and Its Implications in Orbital Inflammatory Disease

Objective IgG4-related disease is an emerging clinical entity which frequently involves tissue within the orbit. In order to appreciate the implications of IgG4 immunostaining, we analyzed gene expression and the prevalence of IgG4- immunostaining among subjects with orbital inflammatory diseases. Methods We organized an international consortium to collect orbital biopsies from 108 subjects including 22 with no known orbital disease, 42 with nonspecific orbital inflammatory disease (NSOI), 26 with thyroid eye disease (TED), 12 with sarcoidosis, and 6 with granulomatosis with polyangiitis (GPA). Lacrimal gland and orbital adipose tissue biopsies were immunostained for IgG4 or IgG secreting plasma cells. RNA transcripts were quantified by Affymetrix arrays. Results None of the healthy controls or subjects with TED had substantial IgG4 staining. Among the 63 others, the prevalence of significant IgG4-immunostaining ranged from 11 to 39% depending on the definition for significant. IgG4 staining was detectable in the majority of tissues from subjects with GPA and less commonly in tissue from subjects with sarcoidosis or NSOI. The detection of IgG4+ cells correlated with inflammation in the lacrimal gland based on histology. IgG4 staining tissue expressed an increase in transcripts associated with inflammation, especially B cell-related genes. Functional annotation analysis confirmed this. Conclusion IgG4+ plasma cells are common in orbital tissue from patients with sarcoidosis, GPA, or NSOI. Even using the low threshold of 10 IgG4+ cells/high powered field, IgG4 staining correlates with increased inflammation in the lacrimal gland based on histology and gene expression.

FUNCTIONAL AND STRUCTURAL CHARACTERISTICS OF EXPERIMENTAL FK 506 NEPHROTOXICITY

1. FK 506 (Tacrolimus, Prograf®) is a novel Immunosuppressant which is effective in solid organ transplantation and autoimmune diseases. The lack of a suitable animal model has hindered the study of the nephrotoxicity of the drug which has emerged as a common adverse effect in clinical trials. We report both acute and chronic nephrotoxicity with tacrolimus (FK) in which renal structure and function are worsened by sodium depletion.

Clinically silent progressive renal tubulointerstitial disease during cisplatin chemotherapy

Background. Chronic cisplatin nephrotoxicity is well documented in animal models but not well characterized in humans. The authors report a 56‐year‐old woman who had end‐stage chronic tubulointerstitial nephropathy develop during treatment with multiple courses of cisplatin chemotherapy for ovarian carcinoma.