Low body weight is a risk factor for proteinuria in multiracial Southeast Asian pediatric population

We examined the impact of low birth weight and low current body weight on proteinuria in a cohort of children participating in the pilot study of a nationwide screening program. Two thousand eighty-three children underwent screening examinations, including birth history, anthropometric measures, blood pressure measurements, and urinalysis. On this study, children with proteinuria were found to have significantly lower mean body weights compared with children without proteinuria (38.7 +/- 7.6 versus 42.8 +/- 11.0 kg; P < 0.001). Progressively decreasing body weights were associated with increasing degrees of proteinuria (42.8 +/- 11.0, 38.9 +/- 7.6, and 37.2 +/- 8.5 kg for 0, 30, and 100 mg/dL of protein, respectively; P = 0.05). When examined by multiple logistic regression, low body weight was associated with a 1.8-fold greater risk (95% confidence interval, 1.27 to 2.64; P = 0.0019) for proteinuria after adjusting for potential confounders. There were trends for lower birth weights in children with proteinuria (3,047.6 +/- 445.2 versus 3,175.0 +/- 608.6 g for proteinuric and nonproteinuric groups, respectively; P = 0.275) and a greater prevalence of children with birth weights less than the 25th percentile (31.3% versus 25.0%; P = 0.786). The relationship between low current body weight and proteinuria was not explained by differences in blood pressure. In conclusion, low current body weight had a stronger relationship with proteinuria than low birth weight in this pediatric population. We hypothesize that the effect of low birth weight on renal disease may be significantly enhanced by environmental factors that result in a low current body weight.

Biopsy-proved acute tubulointerstitial nephritis and toxic epidermal necrolysis associated with vancomycin

A 70-year-old man receiving vancomycin for a methicillin-resistant Staphylococcus aureus (MRSA) abscess developed a drug-induced hypersensitivity reaction with rash, eosinophilia, and acute renal failure requiring dialysis. Renal biopsy revealed diffuse and marked interstitial and tubular infiltration by mononuclear cells and eosinophils; acute tubulointerstitial nephritis (TIN) was diagnosed. The rash progressed to erythema multiforme major after rechallenge with vancomycin in the setting of MRSA peritoneal catheter-related peritonitis and then to fatal toxic epidermal necrolysis in the setting of steroid taper and persistent serum vancomycin levels. This case further implicates vancomycin as a drug that infrequently can cause severe acute TIN and exfoliative dermatitis. When a renally excreted drug such as vancomycin is administered, serum drug levels should be serially monitored and high-dosage steroids be maintained or tapered slowly until serum drug levels become undetectable.

Funding ESRD care through charity: the paradigm of the National Kidney Foundation of Singapore

Given the prohibitive costs of end-stage renal disease (ESRD) care for certain countries and the increasing incidence of ESRD worldwide, alternative methods of funding dialysis care are increasingly necessary. We describe the paradigm of the National Kidney Foundation of Singapore (NKF-S), the provider of subsidized dialysis care and comprehensive rehabilitative services to approximately 60% of all ESRD patients in the country, whose activities are funded entirely by charitable public donations. Unique to the NKF-S model are the considerations of the donor as an "investor" in the health care of NKF-S dialysis patients, the personal responsibility of the dialysis patient as a recipient of this "investment" to play an active role in achieving good clinical and rehabilitative outcomes, and the fostering of community-based support systems to facilitate patient rehabilitation such as partnerships with employers willing to employ dialysis patients. The success of the system is shown by its clinical outcomes, which approximate those observed in the United States. We believe that several aspects of the NKF-S model for ESRD care may be implemented in other communities, particularly in countries that have yet to develop financially and clinically mature dialysis programs.

The molecular pathogenesis and experimental therapy of IgA nephropathy: recent advances and future directions

In 1968 Berger and Hinglais published the first description of IgA nephropathy (IgAN). In the ensuing 30 years, extensive clinical, epidemiologic, and immunologic characterizations of primary (idiopathic) glomerulonephritis with IgA as the predominant or co-dominant immunoglobulin deposited in the mesangia of all glomeruli, have established the features of IgAN as a distinct glomerular disease entity. Despite these efforts, the basic molecular mechanism(s) which mediate abnormal mesangial IgA deposition with ensuing extracellular matrix expansion and mesangial cell proliferation remains poorly understood, definitive diagnosis still depends on histologic examination of renal biopsy specimens, and widely accepted standards for effective therapy remain to be defined. This review will begin with a summary of the earlier 'descriptive' histopathologic and clinical epidemiologic work which firmly established the distinct immunohistologic features of IgAN, the most common glomerulonephritis among patients undergoing renal biopsy and a major cause of renal failure worldwide. In recent years, a series of important advances in the areas of molecular pathogenesis and experimental therapy have emerged, reflected in a "molecular" paradigm shift in the techniques and approaches applied to the study of IgAN. Representative studies will be critically evaluated to highlight both the strengths and potential weaknesses of each of these approaches. Throughout, the author will offer a personal perspective on promising areas of new investigation and potential approaches to the identification of disease/susceptibility genes involved in the development and progression of IgAN, the application of these discoveries through the development of clinically useful molecular diagnostic tests, and the rational design of novel therapeutic strategies.

Haptoglobin reduces renal oxidative DNA and tissue damage during phenylhydrazine-induced hemolysis

BACKGROUND

Haptoglobin knockout (Hp-/-) mice are more sensitive to phenylhydrazine-induced hemolysis than Hp+/+ mice.

METHODS

Hemolysis was induced in Hp-/- and Hp+/+ mice using phenylhydrazine. Relative renal tissue damage and function were then assessed.

RESULTS

Hp-/- mice had higher basal levels of renal lipid peroxidation, as evidenced by levels of malonaldehyde and 4-hydroxy-2(E)-nonenal (MDA/HNE). After the administration of phenylhydrazine, levels of 8-hydroxyguanine (but not other products of oxidative DNA damage) were significantly elevated in the renal DNA. There was also increased induction of heme oxygenase-1. The more severe renal damage in Hp-/- mice was also evident in the delayed erythropoietin gene expression and poorer renal clearance of 3H-inulin. This reduction in glomerular filtration function in Hp+/+ and Hp-/- mice could be restored to baseline by vasodilators (prazosin or diazoxide), implicating renal vasoconstriction as a major mechanism of acute renal failure during induced hemolysis. Precipitation of hemoglobin in the kidney was not increased in Hp-/- mice.

CONCLUSIONS

Haptoglobin appears to play an important physiological role as an antioxidant, particularly during hemolysis.

Evidence for genetic factors in the development and progression of IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is the most common glomerulonephritis in the world among patients undergoing renal biopsy. Once considered a relatively benign condition, longitudinal follow-up studies have revealed that in fact 9 to 50% of patients progress to end-stage renal disease within 20 years of disease onset. In the three decades since its first description by Jean Berger and Nicole Hinglais, clinical, epidemiologic, and immunologic studies of the pathogenesis of primary (idiopathic) mesangial glomerulonephritis with predominant IgA deposits have characterized the features of IgAN as a distinct glomerular disease entity. However, the basic molecular mechanism(s) underlying abnormal IgA deposition in the mesangium with ensuing extracellular matrix expansion and mesangial cell proliferation remains poorly understood. The task of elucidating the molecular basis of IgAN is made especially challenging by the fact that both environmental and genetic components likely contribute to the development and progression of IgAN.

METHODS AND RESULTS

We review here the evidence for genetic factors in the development and progression of IgAN, including a reappraisal of earlier conflicting results from small immunogenetic case-control studies, the evidence for racial differences in the prevalence of IgAN, a detailed summary of all reported occurrences of familial IgAN worldwide, and an exhaustive review of new insights gained through the study of two murine models of hereditary IgAN: the ddY and the uteroglobin-deficient mouse.

CONCLUSIONS

With the development of powerful molecular genetic approaches to the study of both Mendelian and complex human genetic diseases, and the successful efforts of investigators to identify and clinically characterize large IgAN multiplex families, we propose that genetic analysis of familial IgAN is the most promising approach to the identification of IgAN disease/susceptibility genes. Alternatively, if the case-control study design is employed to identify associations between particular candidate genes or markers and the development of IgAN, spurious associations caused by the effects of population stratification should be ruled out by confirming the findings using powerful and sensitive family-based methodologies such as the transmission/dysequilibrium test (TDT).

Somatisation among Asian refugees and immigrants as a culturally-shaped illness behaviour

Epidemiological studies indicate a high prevalence of major depression and anxiety disorder (including post-traumatic stress disorder) among Asian refugees and immigrants living in North America. Yet there exists an alarming underutilization of mental health services and underdiagnosis of psychiatric illness in this rapidly growing minority group. In order to investigate a culturally-derived basis for these observations, a critical review was conducted on descriptive epidemiologic, sociologic, and anthropologic studies of psychiatric illness among Asians and Asian refugees and immigrants reported in the general psychiatric and trans-cultural psychiatric literature of the past forty years. Studies examining the mode of illness presentation among Asian refugees seeking medical care suggest a marked tendency to articulate somatic rather than affective complaints when serious underlying psychiatric conditions exist. In this context, somatisation among Asian refugees and immigrants may reflect culturally-shaped beliefs regarding notions of disease aetiology and treatment as well as what is deemed culturally-appropriate help-seeking behaviour during illness. Misdiagnosis and underdiagnosis of psychiatric illness in this and other minority populations can be minimised by establishing pluralistic norms and multidimensional criteria which take into account the ethnically diverse manifestations of illness behaviour encountered increasingly in Western primary care and psychiatry clinics.

Acute compartment syndrome in a hypothyroid patient

Acute compartment syndrome (ACS) is caused by conditions that either decrease the size of the compartment of increase the content of the compartment. Intracompartmental pressures are raised, thereby initiating a sequence of events that results in myoneural injury. Although limb trauma is the most common and well-organized etiology of ACS, the cause is frequently not readily apparent. Thyroid disease is not a commonly recognized cause of ACS; only one case of ACS associated with hypothyroidism has been previously reported. We now describe a second case of ACS in a patient with severe hypothyroidism and discuss the possible pathogenesis of this association.

Renal angiomyolipoma with a prominent angiomatous component and extramedullary hematopoiesis: a case report

Renal angiomyolipoma is a benign tumor of hamartomatous nature. A case of asymptomatic renal angiomyolipoma in a 57-year-old female is reported. Her right renal mass was incidentally discovered during the evaluation of acute hepatitis by abdominal sonography. She received right simple nephrectomy. The renal pelvic tumor was found to be an angiomyolipoma with a prominent angiomatous component containing hematopoietic elements. Unfortunately, the patient died of peritoneal carcinomatosis because of adenocarcinoma of the transverse colon five years later.

Brown bowel syndrome: report of two cases

Brown bowel syndrome is a rare intestinal disorder associated with the deposition of lipofuscin pigment in the smooth muscle cells. We report two such cases presenting with intestinal pseudo-obstruction, abdominal pain, and body weight loss. Both cases had malabsorption and fatty liver. Exploratory laparotomy revealed brownish discoloration of the small bowel wall and enlargement of mesenteric lymph nodes. Light microscopy, autofluorescence and ultrastructure studies confirmed the deposition of lipofuscin pigments in the intestinal muscle cells and reticuloendothelial cells of mesenteric lymph nodes. In addition, the calf muscle biopsy of case 1 displayed myopathy and fatty replacement. Skeletal muscle strength of both patients was partially restored after parenteral and oral vitamin E supplement and other conservative treatment, but gastrointestinal symptoms of both patients continued to deteriorate. Thus, brown bowel syndrome associated with prolonged and severe malnutrition and possibly vitamin E deficiency appears only partially responsive to vitamin E supplementation.

The involvement of a LINE-1 element in a DNA rearrangement upstream of the mdr1a gene in a taxol multidrug-resistant murine cell line

Two closely related but functionally distinct P-glycoprotein isoforms are encoded by the murine multidrug-resistance genes mdr1a and mdr1b. In a series of independently selected multidrug-resistant (MDR) J774.2 cell lines, mdr gene amplification and/or overexpression and overproduction of either the mdr1a or mdr1b products, or both gene products, correlates with the MDR phenotype. To investigate the possibility that mutations in the promoter regions of the mdr1a or mdr1b genes could influence their differential expression, mdr promoter-specific probes were used to detect and map potential structural alterations. An unusual structural rearrangement was found in the 5'-region of the amplified mdr1a allele in J7.T1, a cell line selected with taxol. To characterize this rearrangement, the regulatory regions of the mdr1a and mdr1b genes were analyzed. Whereas no gross structural alterations were detected by Southern blot hybridization using the mdr1b promoter probe, a novel amplified EcoRI fragment was detected by the mdr1a promoter probe. To determine the precise nature of this mutation, an mdr1a 5'-genomic clone was isolated from J7.T1 cells. Sequence analysis revealed an unusual DNA rearrangement consisting of the mdr1b gene, from its fourth intron toward its 3'-end, upstream of an intact mdr1a promoter on the amplified allele. We propose that this event occurred by an unequal sister chromatid exchange that was mediated by LINE-1 repetitive elements.

Biochemical and genetic characterization of the multidrug resistance phenotype in murine macrophage-like J774.2 cells

The development of multidrug resistance (MDR) in malignant tumors is a major obstacle to the treatment of many cancers. MDR sublines have been derived from the J774.2 mouse macrophage-like cell line and utilized to characterize the phenotype at the biochemical and genetic level. Two isoforms of the drug resistance-associated P-glycoprotein are present and distinguishable both electrophoretically and pharmacologically. Genetic analysis has revealed the presence of a three-member gene family; expression of two of these genes, mdr1a and mdr1b, is associated with MDR whereas the expression of the third, mdr2, is not. Studies of these three genes have revealed similarities and differences in the manner in which they are regulated at the transcriptional level, and have suggested that post-transcriptional effects may also be important.

Structural and functional analysis of the mouse mdr1b gene promoter

The overproduction of P-glycoprotein, an integral membrane protein thought to function as a drug efflux pump, is the hallmark of the multidrug resistance phenotype. In murine multidrug resistant J774.2 cell lines, distinct mdr genes, mdr1a and mdr1b, encode unique P-glycoprotein isoforms. To examine the transcriptional regulation of the mdr1b gene, its promoter was isolated and characterized. The transcription initiation site was mapped by primer extension, and the 5'-flanking region was sequenced. Several potential regulatory elements were identified in this region. A transient expression vector was constructed by fusion of 540 base pairs of 5'-flanking sequence and part of the first untranslated exon to the chloramphenicol acetyltransferase (CAT) gene. When transfected into monkey kidney COS-1, rat pituitary GH3 or T47D human breast cells, the mdr1b 5'-flanking sequences were capable of driving CAT expression. Transient transfection studies using deletion subclones of the mdr1b-CAT construct were done to locate potential cis-acting sequences. The studies indicate the presence of cis-acting elements in the 5'-flanking region of the mdr1b gene. The implications of these findings for expression and regulation of the mdr1b gene are discussed.

Structural analysis of the mouse mdr1a (P-glycoprotein) promoter reveals the basis for differential transcript heterogeneity in multidrug-resistant J774.2 cells

In multidrug-resistant mouse J774.2 cells, the differential overproduction of functionally distinct phosphoglycoprotein isoforms reflects the amplification or transcriptional activation or both of two mdr gene family members, mdr1a and mdr1b. The mdr1a gene is a complex transcriptional unit whose expression is associated with multiple transcript sizes. Independently selected multidrug-resistant J774.2 cell lines differentially overexpress either 4.6- and 5.0-kilobase (kb) or 4.7- and 5.1-kb mdr1a transcripts. However, abundant overproduction of the mdr1a gene product was observed only in cell lines which overexpressed the 4.6- and 5.0-kb mRNAs. In order to determine the basis for mdr1a transcript heterogeneity and the relationship between transcript size and steady-state mdr1a protein levels, genomic and cDNA sequence analyses of the 5' and 3' ends of the mdr1a gene were carried out. Promoter sequence analysis and primer extension mapping indicated that mdr1a transcripts were differentially initiated from two putative promoters to generate either 5.1- and 4.7-kb or 5.0- and 4.6-kb transcripts in four multidrug-resistant J774.2 cell lines. Sequence analysis of 3' cDNA variants and a 3' genomic fragment revealed that the 5.1- and 5.0-kb mRNAs had identical 3'-untranslated regions which differed from those of the 4.7- and 4.6-kb mRNAs as a result of the utilization of a more downstream alternative poly(A) addition signal. Transcript initiation from the putative upstream promoter correlated with a 70 to 85% decrease in steady-state mdr1a protein levels relative to transcript levels. In addition, the identification of putative AP-1 and AP-2 promoter elements suggests a possible role for protein kinase A and protein kinase C in the regulation of mdr1a. The implications of these findings for mdr gene expression and regulation are discussed.

Differential transport properties of two mdr gene products are distinguished by progesterone

P-glycoprotein is an integral membrane protein that is overproduced in multidrug-resistant cells. It is likely to function as an energy-dependent drug efflux pump to maintain intracellular drug concentrations below cytotoxic levels. Individually isolated multidrug-resistant murine cell lines, J7.V1-1 and J7.V3-1, overproduce P-glycoproteins encoded by the mdr1b and mdr1a genes, respectively. The transport properties of these cell lines and the drug binding characteristics of their P-glycoproteins have been compared. It is concluded that 1) the mdr1a gene product is a more efficient efflux pump than the mdr1b gene product, and 2) whereas a single class of vinblastine binding sites is present in J7.V1-1 membrane vesicles, there appears to be two classes of such sites in J7.V3-1 membrane vesicles. The effects of verapamil and progesterone, two compounds that are known to interact with P-glycoprotein, have been analyzed in the two cell lines. Progesterone inhibited drug binding and efflux and increased drug sensitivity to vinblastine with more potency in J7.V1-1 cells than in J7.V3-1 cells. It is concluded that progesterone, but not verapamil, can be used to differentiate the two mdr gene products in the mouse.

Alternate overexpression of two P-glycoprotein [corrected] genes is associated with changes in multidrug resistance in a J774.2 cell line

In multidrug-resistant murine J774.2 cells, the mdr1a and mdr1b genes encode the 120- and 125-kDa P-glycoprotein precursors, respectively (Hsu, S. I., Lothstein, L., and Horwitz, S.B. (1989) J. Biol. Chem. 264, 12053-12062). It is shown here that a J774.2 cell line selected for vinblastine resistance (J7.V3) switched from the 125- to 120-kDa precursor when cells that were maintained in 20 nM vinblastine were grown in 40 nM vinblastine for 20 months. The rate of switching was accelerated by growing cells in higher levels of vinblastine. These findings suggest that cells which express mdr1a have a selective growth advantage compared to cells which express mdr1b. Consistent with this hypothesis, the switching event that occurs in cells maintained at 40 nM vinblastine was correlated with 3.5-5-fold higher levels of resistance to vinblastine, taxol, and doxorubicin in the absence of any detectable increase in the amount of immunoreactive P-glycoprotein. These findings suggest that P-glycoproteins derived from mdr1a and mdr1b are functionally distinct.

Differential overexpression of three mdr gene family members in multidrug-resistant J774.2 mouse cells. Evidence that distinct P-glycoprotein precursors are encoded by unique mdr genes

A hallmark of the multidrug-resistant phenotype is the overproduction of a family of 130-180-kDa integral membrane phosphoglycoproteins collectively called P-glycoprotein. Gene-specific hybridization probes were derived from three classes of mouse P-glycoprotein cDNAs. These probes revealed the differential amplification and/or transcriptional activation of three distinct but closely related mdr genes (mdr1a, mdr1b, and mdr2) in independently selected multidrug-resistant J774.2 mouse cell lines. Overexpression of mdr1a and mdr1b was found to correlate, in general, with the differential overproduction of either a 120- or 125-kDa P-glycoprotein precursor, respectively. This same correlation was observed in a single cell line during the course of stepwise selection for resistance to vinblastine in which a switch in gene expression from mdr1b to mdr1a resulted in a switch from the 125- to 120-kDa P-glycoprotein precursor. These findings suggest that differential overexpression of distinct mdr genes which encode unique P-glycoprotein isoforms is a possible mechanism for generating diversity in the multidrug-resistant phenotype.