Is the urinary biomarkers assessment a non-invasive approach to tubular lesions of the solitary kidney?

Why is chronic kidney disease progressive? Evolutionary adaptations and maladaptations

Despite significant advances in renal physiology, the global prevalence of chronic kidney disease (CKD) continues to increase. The emergence of multicellular organisms gave rise to increasing complexity of life resulting in trade-offs reflecting ancestral adaptations to changing environments. Three evolutionary traits shape CKD over the lifespan: 1) variation in nephron number at birth, 2) progressive nephron loss with aging, and 3) adaptive kidney growth in response to decreased nephron number. Although providing plasticity in adaptation to changing environments, the cell cycle must function within constraints dictated by available energy. Prioritized allocation of energy available through the placenta can restrict fetal nephrogenesis, a risk factor for CKD. Moreover, nephron loss with aging is a consequence of cell senescence, a pathway accelerated by adaptive nephron hypertrophy that maintains metabolic homeostasis at the expense of increased vulnerability to stressors. Driven by reproductive fitness, natural selection operates in early life but diminishes thereafter, leading to an exponential increase in CKD with aging, a product of antagonistic pleiotropy. A deeper understanding of the evolutionary constraints on the cell cycle may lead to manipulation of the balance between progenitor cell renewal and differentiation, regulation of cell senescence, and modulation of the balance between cell proliferation and hypertrophy. Application of an evolutionary perspective may enhance understanding of adaptation and maladaptation by nephrons in the progression of CKD, leading to new therapeutic advances.

Physiology and Pathophysiology of Compensatory Adaptations of a Solitary Functioning Kidney

Children born with a solitary functioning kidney (SFK) have an increased risk of hypertension and kidney disease from early in adulthood. In response to a reduction in kidney mass, the remaining kidney undergoes compensatory kidney growth. This is associated with both an increase in size of the kidney tubules and the glomeruli and an increase in single nephron glomerular filtration rate (SNGFR). The compensatory hypertrophy and increase in filtration at the level of the individual nephron results in normalization of total glomerular filtration rate (GFR). However, over time these same compensatory mechanisms may contribute to kidney injury and hypertension. Indeed, approximately 50% of children born with a SFK develop hypertension by the age of 18 and 20–40% require dialysis by the age of 30. The mechanisms that result in kidney injury are only partly understood, and early biomarkers that distinguish those at an elevated risk of kidney injury are needed. This review will outline the compensatory adaptations to a SFK, and outline how these adaptations may contribute to kidney injury and hypertension later in life. These will be based largely on the mechanisms we have identified from our studies in an ovine model of SFK, that implicate the renal nitric oxide system, the renin angiotensin system and the renal nerves to kidney disease and hypertension associated with SFK. This discussion will also evaluate current, and speculate on next generation, prognostic factors that may predict those children at a higher risk of future kidney disease and hypertension.

Is ciprofloxacin safe in patients with solitary kidney and upper urinary tract infection?

The solitary kidney (SK) undergoes adaptive phenomena of hyperfunction and hyperfiltration. These secondary adaptive phenomena can make it more vulnerable to potentially nephrotoxic therapies. Adverse reactions of the kidneys to ciprofloxacin are rare, but sometimes severe. Therefore, our study sought to assess the reactions to ciprofloxacin of patients with solitary kidney (SK) and urinary tract infection (UTI) by means of urinary biomarkers. We studied 19 patients with SK and urinary tract infection (UTI) who had been administered a 7-day treatment with intravenous ciprofloxacin. Urinary N-acetyl-beta-d-glucosaminidase, alpha 1-microglobulin, and estimated glomerular filtration rate (eGFR) of these patients were measured at the initiation and at the end of treatment. In 47.37% patients NAG diminished under ciprofloxacin treatment. This observation has the significance of favourable evolution of the tubulointerstitial lesions caused by UTI and lack of nephrotoxic effects; 52.63% cases presented an increase of urinary NAG, a fact that suggests a nephrotoxic effect of ciprofloxacin. The evolution of urinary alpha 1-microglobulin was similar to that one of urinary NAG. Only one of three cases with chronic kidney disease (CKD) stage 5 presented acute kidney injury, associated with increase in the tubular markers. In spite of the high variability of the urinary biomarkers, UTI evolved favourably in these cases; eGFR increased in 16 out of 19 patients, a fact which is indicative of a good outcome of renal function, even in patients with elevated levels of the tubular damage biomarkers. This observation supports the hypothesis that eGFR may be dissociated from the biomarkers which assess tubular injury. In SK patients the occurrence of AKI is not frequent, although the urinary biomarkers rise in some patients treated with ciprofloxacin. This is related not only to the nephrotoxic effect of the drug, but probably to the association of other factors (allergy, individual susceptibility). In SK patients, renal tubular biomarkers, especially NAG, allow monitoring of tubular injury and impose caution in prescribing ciprofloxacin treatment, mainly to patients at risk. Ciprofloxacin is relatively safe regarding its nephrotoxicity, while caution is required in vulnerable patients.

A forward to optimization of antivenom therapy: An in vivo study upon the effectiveness of the antivenom against early and delayed nephrotoxicity induced by the venom of the Iranian scorpion Hemiscorpius lepturus in rat

The aim of the present in vivo study was to identify the optimal effective dose, the most favorable time and the route of administration of the available polyvalent scorpion antivenom against the toxic effects induced by Hemiscorpius lepturus (H. lepturus) venom in rat. The end point for assessment included measurement of alanin-amino-peptidase (AAP) and N-acetyl-b-d-glucosaminidase (NAG), biochemical urine analysis and histopathological assessment. The results showed that a single subcutaneous 50 μg of the venom produced significant increase in the AAP and NAG enzyme activity, urinary biochemical parameters and induced histopathological structural abnormalities in the renal system. The optimal effective co-administered dose of the antivenom was 0.5 ml, which when administered 1 and 2 h of envenomation by intravenous (IV) and subcutaneous (SC) routes respectively produced significant protection against these toxic effects. Prudently, the significance of these findings need to be assessed in further clinical studies.