Proteinuria

1. Proteinuria Plasma proteins - essential components of any living being The kidneys play a major role in the retention of plasma proteins glomerular filtration barrier renal tubules reabsorption of the passing through glomerular filtration barrier proteins

2. Proteinuria The glomerular capillary wall - charge and size-selective properties high-molecular-weight (HMW) plasma proteins can not enter the urinary space only a tiny fraction of albumin, globulin, and other large plasma proteins cross LMW proteins (<20,000 Da) cross capillary wall they are normally reabsorbed by the proximal tubule

3. Proteinuria Most healthy individuals excrete 30 and 130 mg/day of protein the upper limit of normal total urine protein excretion - 150 to 200 mg/day for adults the upper limit of normal albumin excretion - 30 mg/day

4. Proteinuria Normal tubular protein secretion  a very small amount of protein that normally appears in the urine Tamm-Horsfall protein (uromodulin) HMW glycoprotein (23 × 106 Da) formed on the epithelial surface of the thick ascending limb of the loop of Henle and early distal convoluted tubule binds and inactivates the cytokines interleukin-1 and tumor necrosis factor Immunoglobulin A (IgA) Urokinase

5. Proteinuria Normal urine protein excretion up to 150 mg/d the detection of abnormal quantities or types of protein in the urine - an early sign of significant renal or systemic disease Normal urine albumin excretion less than 5 mg/L low levels of albumin excretion = microalbuminuria linked to the identification of the early stages of diabetic kidney disease Microalbuminuria excretion of 30-300 mg/d or 20-200 µg/min too small to be detected by routine dipstick screening

6. Proteinuria Abnormal amounts of protein in the urine – three/four mechanisms glomerular proteinuria disruption of the capillary wall barrier  a large amount of HMW plasma proteins that overwhelm the limited capacity of tubular reabsorption and cause protein to appear in the urine tubular proteinuria tubular damage or dysfunction inhibit the normal resorptive capacity of the proximal tubule increased amounts of mostly LMW proteins appear in the urine increased production of normal or abnormal plasma proteins can be filtered at the glomerulus and overwhelms the resorptive capacity of the proximal tubule (!!) rarely - increased urine protein due to increased tubular production of protein

7. Proteinuria β2-Microglobulin an LMW (11.8-kDa) protein identified as the light chain of class I major histocompatibility antigens (e.g., human leukocyte antigens [HLAs] A, B, and C) freely filtered at the glomerulus  avidly taken up and catabolized by the proximal tubule detectable urinary levels of β2-microglobulin - associated with many pathologic conditions involving the proximal tubule aminoglycoside Balkan endemic nephropathy heavy metal nephropathies radiocontrast nephropathy kidney transplant rejection useful in distinguishing upper from lower urinary tract infection.

8. Proteinuria Bence Jones protein immunoglobulin light chains filtered at the glomerulus plasma cell dyscrasias may produce monoclonal proteins, immunoglobulin, free light chains, and a combination of these the detection of urine immunoglobulin light chains can be the first clue to a number of important clinical syndromes associated with plasma cell dyscrasias that involve the kidney plasma cell dyscrasias may also manifest as proteinuria or albuminuria when the glomerular deposition of light chains causes disruption of the normally impermeable capillary wall (!!)

9. Proteinuria Selective or nonselective proteinuria glomerular proteinuria can be further characterized as selective or nonselective a clearance ratio of immunoglublin G (IgG; an HMW protein)–to-albumin that is less than 0.10 = selective proteinuria more often seen in patients with minimal change disease predicts a good response to treatment with corticosteroids IgG-to-albumin clearance ratios greater than 0.50 = nonselective pattern the cost of the protein separation procedures has limited their widespread clinical use

10. Proteinuria Glomerular proteinuria / tubular proteinuria higher amounts of albumin and HMW proteins suggest glomerular proteinuria nephrotic range >3 g/24 hr  certain glomerular source isolated increases in LMW protein fractions are more suggestive of tubular proteinuria it is unusual for tubular proteinuria to exceed 1 to 2 g/day only a small fraction of protein excretion due to tubular damage should be albumin tubular proteins are heterogeneous; α2-microglobulin is often a major constituent

11. Proteinuria Techniques to Measure Urine Protein in random samples in timed or untimed overnight samples in 24-hour collections source of error - inaccurate urine collection particularly 24-hour collections

12. Proteinuria Techniques to Measure Urine Protein Tests to accurately quantitate total protein concentration in urine rely on precipitation(sulfosalicylic acid is added to a sample of urine, and the turbidity is measured with a photometer or a nephelometer) Tests to estimate total protein concentration in urine chemically impregnated plastic strips (dipstick)

13. Proteinuria Techniques to Measure Urine Protein Tests to accurately quantitate total protein concentration in urine (precipitation) proteins detected: γ-globulin light chains, albumin the method is more sensitive to albumin than to globulins trichloroacetic acid can be used in place of sulfosalicylic acid to increase the sensitivity to γ-globulin (eg for Bence Jones protein) Tests to estimate total protein concentration in urine(dipstick) pH-sensitive colorimetric indicator that changes color when negatively charged proteins bind to it positively charged proteins are less detected  immunoglobulin light chains may escape urine dipstick detection even when present in large amounts in the urine sensitive to very small urine protein concentrations -the lower limit of detection 10-20 mg/dL (could be Tamm-Horsfall protein)

14. Proteinuria Techniques to Measure Urine Protein quantitative determinations of albuminas gold standards Radioimmunoassay Immunoturbimetric technique Enzyme-linked immunosorbent assay (ELISA)

15. Proteinuria Techniques to Measure Urine Protein Screening methods dipstick = qualitative or semiquantitative for total protein excretion and microalbuminuria sensitivity and specificity - markedly influenced by fluid intake, state of diuresis, and the resulting urine concentration protein-to-creatinine or albumin-to-creatinine ratio in random, or timed urine collections there is a high degree of correlation between 24-hour urine protein excretion and protein-to-creatinine ratios in random, single-voided urine samples in patients with a variety of kidney diseases

16. Proteinuria Techniques to Measure Urine Protein Screening methods - protein-to-creatinine or albumin-to-creatinine ratio more quantitative than a simple dipstick screening procedure a protein-to-creatinine ratio of greater than 3.0 or 3.5 mg/mg or less than 0.2 mg/mg indicates protein excretion rates of greater than 3.0 or 3.5 g/24 hr or less than 0.2 g/24 hr

17. Proteinuria Analytic tools - to separate and identify individual urinary proteins agarose gel electrophoresis column gel chromatography polyacrylamide gel electrophoresis immunoelectrophoresis isoelectric focusing proteomic techniques employing mass spectrometry peptide mass fingerprinting have been used in clinical laboratories to determine the selectivity of urine protein to identify monoclonal immunoglobulin heavy and light chains

18. Proteinuria β2-Microglobulin commonly measured in urine using radioimmunoassay or ELISA Bence Jones protein immunoglobulin light chains may not be detected by dipstick a proteinuria or albuminuria may also exists when the glomerular deposition of light chains causes disruption of the normally impermeable capillary wall monoclonal proteins are best detected using serum and urine immunoelectrophoresis the diagnosis of a plasma cell dyscrasia can be suspected when a tall, narrow band on electrophoresis suggests the presence of a monoclonal γ-globulin or immunoglobulin light chain

19. Proteinuria Screening methods  establisheddiagnosis of kidney disease Measuring the amount of urine protein (usefull in IgA nephropathy, membranous nephropathy, type I membranoproliferative glomerulonephritis, nephrotic syndrome, mild renal insufficiency ) additional prognostic information can be used to monitor the response to immunosuppressive therapy

20. Proteinuria There are variations of concentration of albumin in the urine with: physical activity level, acute illnesses or fevers, menstruation, pregnancy, vaginal discharge, diet, blood pressure, volume status, degree of glycemic control, and urine collection method (eg, 24 h, overnight or timed, short-term) Albumin excretion - 25% higher during the day than overnight, with a day-to-day variation of 40% before a patient is classified as having microalbuminuria - at least 3 urine samples over a 6-month period that satisfy the above range criterion are recommended

21. Proteinuria The presence of abnormal amounts or types of protein in the urine reflects : A defective glomerular barrier  abnormal amounts of proteins of intermediate molecular weight enter the Bowman space Tubular diseases  inability of the kidneys to normally reabsorb the proteins through the renal tubules Overproduction of plasma proteins pass through the normal glomerular basement membrane (GBM)  enter the tubular fluid in amounts that exceed the capacity of the normal proximal tubule to reabsorb them

22. Proteinuria Symptoms in most patients - asymptomatic proteinuria detected upon screening in patients with hypertension, diabetes frequently in the absence of serious underlying renal disease

23. Proteinuria The more common and benign causes of proteinuria transient proteinuria associated with physical exertion and fever orthostatic proteinuria (albuminuria < 1 g/d, normal renal function) typically - in tall thin adolescents or adults younger than 30 years, +/- severe lordosis overnight urine collection shows normal protein excretion (ie, <50 mg during 8-h period) nonrenal disease (proteinuria < 1 g/d, normal renal function) severe cardiac failure, sleep apnea

24. Proteinuria Microalbuminuria (30-300 mg/d or 20-200 µg/min) frequently observed in association with: Hypertension Early stages of diabetic nephropathy

25. Proteinuria Proteinuria in significant glomerular disease in excess of 500 mg/d particularly associated with: Changes in urine appearance: red/smoky, frothy Edema: ankle, periorbital, labial, scrotal Elevated blood pressure Elevated cholesterol, lipiduria, hypoalbuminemia Active urine sediment (dysmorphic red blood cells,+/-red cell casts) Abnormal renal function

26. Proteinuria Proteinuria in significant glomerular disease Joint discomfort, skin rash, eye symptoms, or symptoms of Raynaud syndrome Multisystem disease : systemic lupus erythematosus, rheumatoid arthritis History of kidney disease (including pregnancy related) Medication, including over-the-counter or herbal remedies Past health problems, such as jaundice, tuberculosis, malaria, syphilis, endocarditis Systemic symptoms, such as fever, night sweats, weight loss, or bone pain Risk factors for HIV or hepatitis Symptoms that suggest complication(s) of nephrotic syndrome Loin pain, abdominal pain, breathlessness, pleuritic chest pain, rigors Associated upper respiratory tract infection

27. How dose proteinuria damage the kidney?

28. How dose proteinuria damage the kidney? glomerulosclerosis is explained by the hyperfiltration theory tubulointerstitial injury is olso induced by proteinuria; this is a final common pathway to eventual kidney failure

29. How dose proteinuria damage the kidney?

30. How dose proteinuria damage the kidney?

31. How dose proteinuria damage the kidney?

32. How dose proteinuria damage the kidney? Albumin - Albumin-bound fatty acids albumin = a major components in proteinuric urine albumin-bound fatty acids = important mediators of tubulointerstitial injury  apoptosis in proximal tubular cells

33. How dose proteinuria damage the kidney?

34. How dose proteinuria damage the kidney? Tubulointerstitial injury induced by proteinuria molecular and cell biological changes up-regulation of certain proinflammatory and profibrogenic gene: MCP-1, osteopontin transdifferentiation of tubular cells into myofibroblasts fibrosis of the kidney a large number of apoptotic cells in the tubulointerstitial compartment apoptosis of tubular cells  atubular glomeruli and decreases the number of functional nephrons

35. How dose proteinuria damage the kidney? Tubulointerstitial injury induced by proteinuria = atubular glomeruli and interstitial fibrosis

36. How dose proteinuria damage the kidney? What mediates tubular and interstitial damage induced by proteinuria?

37. How dose proteinuria damage the kidney?

38. How dose proteinuria damage the kidney? Effects of filtered macromolecules on tubular cells

39. How dose proteinuria damage the kidney?

40. How dose proteinuria damage the kidney? Various components in proteinuric urine damages tubular cells directly: growth factors transferrin albumin albumin-bound fatty acids complement components in proteinuric urine

41. How dose proteinuria damage the kidney? Protein overload in tubular cells is also associated with ammonium production Complement component C3 modified by ammonia = amidated C3  amidated C3 forms the alternative pathway convertase of the complement cascade Preferential secretion of ammonia into the tubular lumen  inappropriate activation of the alternative pathway at the brush border in proteinuric conditions

42. How dose proteinuria damage the kidney? Complement components in proteinuric urine = crucial mediator of tubulointerstitial damage complement is activated in urine of patients with various glomerular diseases the degree of intratubular complement activation correlated with the level of non-selective proteinuria

43. How dose proteinuria damage the kidney?

44. How dose proteinuria damage the kidney? accumulation of inflammatory cells around tubules of high filtered protein load C3 staining in the brush border or within the cytoplasm at sites of high protein reabsorption !! renoprotective effects of ACE inhibitor by limiting tubular activation of complement

45. How dose proteinuria damage the kidney? proteinuria  tubular injury fibrotic changes  duration of proteinuria, quantity of proteinuria, quality of proteinuria, other factors other factors: hypertension, smoking, aging, chronic hypoxia

46. How dose proteinuria damage the kidney? ?

47. How dose proteinuria damage the kidney?

48. How dose proteinuria damage the kidney? ?

49. How dose proteinuria damage the kidney?

50. How dose proteinuria damage the kidney?