An ELISA for the detection of type IV collagen in human urine--application to patients with glomerulonephritis

Drug-induced nephrotoxicity and its biomarkers

Nephrotoxicity occurs when kidney-specific detoxification and excretion do not work properly due to the damage or destruction of kidney function by exogenous or endogenous toxicants. Exposure to drugs often results in toxicity in kidney which represents the major control system maintaining homeostasis of body and thus is especially susceptible to xenobiotics. Understanding the toxic mechanisms for nephrotoxicity provides useful information on the development of drugs with therapeutic benefi ts with reduced side effects. Mechanisms for drug-induced nephrotoxicity include changes in glomerular hemodynamics, tubular cell toxicity, inflammation, crystal nephropathy, rhabdomyolysis, and thrombotic microangiopathy. Biomarkers have been identifi ed for the assessment of nephrotoxicity. The discovery and development of novel biomarkers that can diagnose kidney damage earlier and more accurately are needed for effective prevention of drug-induced nephrotoxicity. Although some of them fail to confer specificity and sensitivity, several promising candidates of biomarkers were recently proved for assessment of nephrotoxicity. In this review, we summarize mechanisms of drug-induced nephrotoxicity and present the list of drugs that cause nephrotoxicity and biomarkers that can be used for early assessment of nephrotoxicity.

Effect of renin-angiotensin-aldosterone system triple blockade on non-diabetic renal disease: addition of an aldosterone blocker, spironolactone, to combination treatment with an angiotensin-converting enzyme inhibitor and angiotensin II receptor blocker

Although dual blockade of the renin-angiotensin-aldosterone system (RAAS) with the combination of an angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker (ARB) is generally well-established as a treatment for nephropathy, this treatment is not fully effective in some patients. Based on the recent evidence implicating aldosterone in renal disease progression, this study was conducted to examine the efficacy of blockade with three different mechanisms by adding an aldosterone blocker in patients who do not respond adequately to the dual blockade. A 1-year randomized, open-label, multicenter, prospective controlled study was conducted, in which 32 non-diabetic nephropathy patients with proteinuria exceeding 0.5 g/day were enrolled after more than 12 weeks of ACE-I (5 mg enalapril) and ARB (50 mg losartan) combination treatment. These patients were allocated into two groups of 16 patients each: a triple blockade group in which 25 mg of spironolactone daily was added to the ACE-I and ARB combination treatment, and a control group in which 1 mg of trichlormethiazide or 20 mg of furosemide was added to the combination treatment instead of spironolactone depending upon the creatinine level. After 1 year of treatment, the urinary protein level decreased by 58% (p<0.05) with the triple blockade but was unchanged in the controls. Furthermore, urinary type IV collagen level decreased by 40% (p<0.05) with the triple blockade but was unchanged in the controls. The decreases in urinary protein and urinary type IV collagen were not accompanied by a decrease in blood pressure. Mean serum creatinine, potassium and blood pressure did not change significantly by either treatment. In conclusion, triple blockade of the RAAS was effective for the treatment of proteinuria in patients with non-diabetic nephropathy whose increased urinary protein had not responded sufficiently to a dual blockade.

Decreased urinary concentrations of type IV collagen in amyotrophic lateral sclerosis

OBJECTIVES

Type IV collagen (IV-C) abnormalities of skin and serum have been reported in patients with amyotrophic lateral sclerosis (ALS). However, there has been no study of urinary IV-C in ALS. The present study investigates urinary IV-C and the relation to its skin content in patients with ALS.

MATERIAL AND METHODS

We studied IV-C immunoreactivity of skin and measured urinary levels of IV-C in ALS patients and controls.

RESULTS

The basement membrane as well as blood vessels of skin in ALS patients was weakly positive for IV-C as compared with those of controls. Immunostaining became even weaker as ALS progressed. The urinary level of IV-C in ALS patients was significantly decreased as compared to diseased controls (P<0.001) and healthy controls (P<0.001), and was negatively and significantly associated with duration of symptoms (r=-0.85, P<0.001). There was an appreciable positive correlation between urinary IV-C levels and the density for IV-C immunoreactivity in ALS patients (r=0.84, P<0.01).

CONCLUSION

These data suggest that a metabolic alteration of IV-C may occur in ALS patients and decreased levels of urinary IV-C may be related to the decreased IV-C immunoreactivity of skin in ALS.

Exposure of human renal proximal tubular cells to glucose leads to accumulation of type IV collagen and fibronectin by decreased degradation

Thickening and reduplication of the tubular basement membrane has been reported as an early event in diabetic nephropathy. In the current study we examined the effects of elevated D-glucose concentrations on human proximal tubular (HPTC) type IV collagen and fibronectin turnover. Incubation of confluent growth arrested HPTC with 25 mM D-glucose led to accumulation of both type IV collagen and fibronectin. This effect was maximal at 48 hours and represented a sevenfold increase for fibronectin (N = 4, P = 0.04), and a threefold increase for type IV collagen (N = 3, P = 0.03) over cells exposed to 5 mM D-glucose controls. This increase was not dependent on new gene transcription for either protein. Tissue inhibitor of metalloproteinases (TIMP 1 + TIMP 2) were induced following addition of 25 mM D-glucose, but not when cells were exposed to 5 mM D-glucose. Twenty-four hours after the addition of 25 mM D-glucose there was an eightfold increase in TIMP 1 (P = 0.009, N = 4), and a tenfold increase in TIMP 2 levels (P = 0.003, N = 4), over the control values for both inhibitors. The increase in both TIMP 1 and TIMP 2 in response to 25 mM D-glucose was abrogated in a dose dependent manner by the aldose reductase inhibitor sorbinil. Gelatin-substrate gel zymography showed increased activity of gelatinase A, but not of gelatinase B in response to the addition of 25 mM D-glucose to HPTC. The induction of gelatinase A was accompanied by increased gelatinase A mRNA expression, which was inhibited both by protein kinase C (PKC) depletion using PMA pre-treatment, and by the addition of a PKC inhibitor. These data demonstrate that the glucose-induced accumulation of type IV collagen and fibronectin is unrelated to increased gene transcription, but may involve alterations in the degradative pathway of these basement membrane constituents. Furthermore, the data demonstrate that glucose may simultaneously activate two intracellular pathways (the polyol pathway and a PKC dependent activation pathway), which are involved in mediating separate, complementary effects on cell function.

Urinary type IV collagen as a marker for early diabetic nephropathy

We investigated the urinary secretion of type IV collagen in 115 subjects with non-insulin-dependent diabetes mellitus (NIDDM) without macroproteinuria, 34 normal healthy subjects and 19 subjects with chronic glomerulonephritis (CGN). We examined the relation between the urinary level of type IV collagen and various clinical parameters. The urinary level of type IV collagen was significantly elevated in NIDDM subjects compared with normal subjects (4.88 +/- 3.12 vs. 1.7 +/- 1.25 micrograms/gCr, P < 0.001). The urinary level of type IV collagen was increased even in NIDDM subjects with normoalbuminuria. The ratio of urinary type IV collagen was significantly lower in subjects with chronic glomerulonephritis (CGN) than those in NIDDM subjects (P < 0.001), although there was no significant difference in the urinary level of type IV collagen between NIDDM and CGN subjects. The ratio of urinary type IV collagen to albumin was under 10.0 x 10(-6) in all subjects with CGN. Our results suggest that measurement of the urinary level of type IV collagen is useful for detection of early diabetic nephropathy and for the differential diagnosis of diabetic nephropathy and chronic glomerulonephritis.

Urinary excretion of type IV collagen and laminin in the evaluation of nephropathy in NIDDM: comparison with urinary albumin and markers of tubular dysfunction and/or damage

To clarify the diagnostic relevance of urinary type IV collagen (IV-C) and laminin in diabetic nephropathy, the excretion of these basement membrane proteins were determined by enzyme immunoassay in 172 non-insulin-dependent diabetic patients with different grades of nephropathy and 64 non-diabetic control subjects, and were evaluated in comparison with those of urinary albumin, N-acetyl-beta-D-glucosaminidase (NAG) and alpha 1-microglobulin (alpha 1MG). These excretions were also compared between a group of non-diabetic renal disease (NDRD) patients (n = 24) and a subgroup of the diabetic patients studied (n = 76), whose urinary albumin excretion (UAE) varied within the ranges of micro- and macroalbuminuria. Of the diabetic patients studied, 49.7%, 53.4% and 32.4% had raised urinary albumin, NAG and alpha 1 MG excretion, respectively. In these patients, 54% and 53% exceeded the upper limit of normal for urinary IV-C and laminin. The level of IV-C and laminin excretion and the prevalence of their abnormal excretion showed a trend to increase with increasing grade of nephropathy, as assessed by UAE. In the normoalbuminuric [UAE < 20 mg/g creatinine (Cr)] stage, 28.3% and 26.3% patients had raised urinary IV-C and laminin excretion, respectively. In this stage, the excretion values for IV-C and laminin also rose significantly even when the UAE was < or = 10 mg/g Cr (P < 0.05 and P < 0.005, respectively). There was a close linear relationship between IV-C and laminin excretion (r = 0.73, P < 0.0001), together with their significant relationships with albumin, NAG and alpha 1MG excretion. The relationship of urinary IV-C and laminin with urinary NAG and alpha 1MG excretion remained significant even in normoalbuminuric patients. The normoalbuminuric patients with raised NAG and/or alpha 1MG excretion also had a higher prevalence of raised IV-C and laminin excretion than those with normal NAG and alpha 1MG excretion. The excretion values for IV-C and laminin, and the excretion ratios for IV-C/albumin and laminin/albumin were significantly higher in diabetic patients with evidence of incipient and clinical nephropathy than in NDRD patients, though the two patient groups had a comparable level of serum Cr and UAE. We conclude that the measurement of urinary IV-C and laminin may have potential for the evaluation of diabetic nephropathy. Furthermore, their determination might be helpful for distinguishing diabetic versus non-diabetic etiologies of altered renal function in diabetic patients.