Background: Diuretic resistance is among the most challenging problems that the cardio-nephrologist must address in daily clinical practice, with a considerable burden on hospital admissions and ...health care costs. Indeed, loop diuretics are the first-line therapy to overcome fluid overload in heart failure patients. The pathophysiological mechanisms of fluid and sodium retention are complex and depend on several neuro-hormonal signals mainly acting on sodium reabsorption along the renal tubule. Consequently, doses and administration modalities of diuretics must be carefully tailored to patients in order to overcome under- or overtreatment. The frequent and tricky development of diuretic resistance depends in part on post-diuretic sodium retention, reduced tubular secretion of the drug, and reduced sodium/chloride sensing. Sodium and chloride depletions have been recently shown to be major factors mediating these processes. Aquaretics and high-saline infusions have been recently suggested in cases of hyponatremic conditions. This review discusses the limitations and strengths of these approaches. Summary: Long-term diuretic use may lead to diuretic resistance in cardio-renal syndromes. To overcome this complication intravenous administration of loop diuretics and a combination of different diuretic classes have been proposed. In the presence of hyponatremia, high-saline solutions in addition to loop diuretics might be beneficial, whereas aquaretics require caution to avoid overcorrection. Key Messages: Diuretic resistance is a central theme for cardio-renal syndromes. Hyponatremia and hypochloremia may be part of the mechanisms for diuretic resistance. Aquaretics and high-saline solutions have been proposed as possible new therapeutic solutions.
Changes in the expression of potassium channels regulate skeletal muscle development. The purpose of this study was to investigate the expression profile and pharmacological role of K(v)7 ...voltage-gated potassium channels in skeletal muscle differentiation, proliferation, and survival after myotoxic insults. Transcripts for all K(v)7 genes (K(v)7.1-K(v)7.5) were detected by polymerase chain reaction (PCR) and/or real-time PCR in murine C(2)C(12) myoblasts; K(v)7.1, K(v)7.3, and K(v)7.4 transcripts were up-regulated after myotube formation. Western blot experiments confirmed K(v)7.2, K(v)7.3, and K(v)7.4 subunit expression, and the up-regulation of K(v)7.3 and K(v)7.4 subunits during in vitro differentiation. In adult skeletal muscles from mice and humans, K(v)7.2 and K(v)7.3 immunoreactivity was mainly localized at the level of intracellular striations positioned between ankyrinG-positive triads, whereas that of K(v)7.4 subunits was largely restricted to the sarcolemmal membrane. In C(2)C(12) cells, retigabine (10 microM), a specific activator of neuronally expressed K(v)7.2 to K(v)7.5 subunits, reduced proliferation, accelerated myogenin expression, and inhibited the myotoxic effect of mevastatin (IC(50) approximately 7 microM); all these effects of retigabine were prevented by the K(v)7 channel blocker 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991) (10 muM). These data collectively highlight neural K(v)7 channels as significant pharmacological targets to regulate skeletal muscle proliferation, differentiation, and myotoxic effects of drugs.
Long-term potentiation (LTP) depends on the coordinated regulation of an ensemble of proteins related to Ca(2+) homeostasis, including Ca(2+) transporters. One of the major players in the regulation ...of intracellular Ca(2+) (Ca(2+)(i)) homeostasis in neurons is the sodium/calcium exchanger (NCX), which represents the principal mechanism of Ca(2+) clearance in the synaptic sites of hippocampal neurons. Because NCX3, one of the three brain isoforms of the NCX family, is highly expressed in the hippocampal subfields involved in LTP, we hypothesized that it might represent a potential candidate for LTP modulation. To test this hypothesis, we first examined the effect of ncx3 gene ablation on NCX currents (I(NCX)) and Ca(2+) homeostasis in hippocampal neurons. ncx3(-/-) neurons displayed a reduced I(NCX), a higher basal level of Ca(2+)(i), and a significantly delayed clearance of Ca(2+)(i) following depolarization. Furthermore, measurement of field EPSPs, recorded from the CA1 area, revealed that ncx3(-/-) mice had an impaired basal synaptic transmission. Moreover, hippocampal slices from ncx3(-/-) mice exhibited a worsening in LTP compared with congenic ncx3(+/+). Consistently, immunohistochemical and immunoblot analysis indicated that in the hippocampus of ncx3(-/-) mice both Ca(2+)/calmodulin-dependent protein kinase IIα (CaMKIIα) expression and the phosphoCaMKIIα/CaMKIIα ratio were significantly reduced compared with ncx3(+/+). Interestingly, ncx3(-/-) mice displayed a reduced spatial learning and memory performance, as revealed by the novel object recognition, Barnes maze, and context-dependent fear conditioning assays. Collectively, our findings demonstrate that the deletion of the ncx3 gene in mice has detrimental consequences on basal synaptic transmission, LTP regulation, spatial learning, and memory performance.
Liver failure is associated to high mortality due to the accumulation of protein-bound metabolites, such as bilirubin, not removed by conventional hemodialysis. Different methods can efficiently ...remove them, such as the molecular adsorbent recirculating system (MARS), plasma exchange (PEX), and bilirubin or plasma adsorption perfusion (PAP). No direct comparison exists between MARS, PEX and PAP, and current guidelines do not specify which method (and when) to use. We have retrospectively evaluated MARS, PEX and PAP in their effectiveness in lowering plasma bilirubin concentration, and their effects on liver and kidney function. A total of 98 patients have been recruited, which comprised 68 patients treated with PAP (177 sessions), 16 patients with PEX (41 sessions) and 11 patients with MARS (21 sessions). Bilirubin, creatinine, liver enzymes were analyzed before and after the first treatment with each technique. The three methods did not differ for bilirubin lowering efficiency, with MARS showing only slightly less effective reductions. Finally, the three techniques did not differ in the amount of change of cholinesterase, but a lower reduction in AST was found using PAP. Our retrospective observation is one of the largest case series of hepatic failure treated with bilirubin absorption. The choice of the technique cannot be based on the desired reduction in bilirubin concentration. Based on costs and duration of treatment, we suggest that PAP could be considered as a first-line approach. In case of kidney involvement, MARS remains a valuable option.
A‐kinase anchor protein 121 (AKAP121) assembles a multivalent signalling complex on the outer mitochondrial membrane that controls persistence and amplitude of cAMP and src signalling to ...mitochondria, and plays an essential role in oxidative metabolism and cell survival. Here, we show that AKAP121 levels are regulated post‐translationally by the ubiquitin/proteasome pathway. Seven In‐Absentia Homolog 2 (Siah2), an E3–ubiquitin ligase whose expression is induced in hypoxic conditions, formed a complex and degraded AKAP121. In addition, we show that overexpression of Siah2 or oxygen and glucose deprivation (OGD) promotes Siah2‐mediated ubiquitination and proteolysis of AKAP121. Upregulation of Siah2, by modulation of the cellular levels of AKAP121, significantly affects mitochondrial activity assessed as mitochondrial membrane potential and oxidative capacity. Also during cerebral ischaemia, AKAP121 is degraded in a Siah2‐dependent manner. These findings reveal a novel mechanism of attenuation of cAMP/PKA signaling, which occurs at the distal sites of signal generation mediated by proteolysis of an AKAP scaffold protein. By regulating the stability of AKAP121‐signalling complex at mitochondria, cells efficiently and rapidly adapt oxidative metabolism to fluctuations in oxygen availability.
The classical approach to the analysis of kidney biopsies is based on semi-quantitative scores of the amount of sclerosis, inflammatory infiltrate, fibrosis and vascular damage. However, advanced ...renal lesions may be accompanied by a paucity of clinical features and, conversely, important clinical abnormalities may be accompanied by minimal histopathological changes. The objective of this study is to correlate new, semiautomatic, quantitative features of kidney biopsies (e.g. fractal analysis) with clinical and hematological parameters using a cross-sectional design.
Whole slide images from sixty-seven biopsies of patients diagnosed for diabetic nephropathy, hypertensive nephropathy, focal segmental glomerulosclerosis (FSGS) or IgA nephropathy have been used. The images have been semi-automatically quantified in the ImageJ environment, in order to derive the glomerular density, the tubular density, the number of tubules per glomerulus and the fractal dimension of the tubular lumen in the cortex (an index of complexity of the tubular lumen). For each patient, hemato-chemical data have been retrieved, including the uric acid level and the creatinine-based eGFR.
A linear relationship between eGFR and glomerular density was observed in hypertension and FSGS, but not in diabetic nephropathy. Conversely, the eGFR correlated with the tubular density across different glomerular conditions. Moreover, the tubular density was linearly correlated with uric acid levels in different pathological conditions. The fractal dimension of tubular lumen was correlated with the eGFR but only in hypertensive patients. Finally, blood pressure was not correlated to any of the morphological indices tested.
We propose the use of the fractal dimension as a new morphological descriptor of the nephron integrity.
Abstract
Background and Aims
The term "inflammation" is undoubtedly one of the oldest medical terms and yet in use. However, its meaning has changed over the centuries. This work gives a historical ...and critical view of the concept of inflammation, with particular reference to kidney diseases.
Method
The term "inflammation" was used in Galenic medicine to specify a collection of symptoms. Celsus (c. 25 BC – c. 50 AD) described "rubor et tumor cum calor et dolor", but the list became much longer in subsequent Galenic scholars. It is interesting to note that one of the inflammation symptoms, "tumor," was then used to indicate cancer (tumor=swelling due to a mass or due to edema). Virchow (1821 –1902) is often quoted for introducing a fifth symptom, "function Lasa", but his significant contribution relies on introducing the microscope to study diseases: thanks to this instrument, the paradigm of inflammation was undergoing a revolution. Thereby, the definition of inflammation shifted from a pure collection of symptoms to a histopathological classification, characterized by the tissue "inflammatory infiltrates" with subcategories according to the cell types involved. Numerous authors added their names to pathology textbooks when describing a new kind of cellular infiltration.
Overall, the tremendous success of the histopathologic paradigm of inflammation or "inflammatory infiltrates" was the possibility to contain and revert this phenomenon with corticosteroids (with few exceptions). Subsequently, specific drugs were proposed for each inflammatory infiltrate. This type of paradigm is still used today to define, e.g., tubulointerstitial nephritis or intra- and peri-glomerular inflammations. The subsequent classification of inflammatory infiltrates using immunohistochemistry did not modify our classification system (the distinction of, e.g., CD20 lymphocytes from CD4 T-cells is not used, unfortunately, in today's classification system).
Results
Towards the 1940s, Avery et al. recognize that some plasma proteins (specifically the famous C-reactive protein) increase during acute infection, which is a typical inflammatory state. This observation led to a new "molecular definition of inflammation". The idea to identify the presence of inflammatory infiltrates in tissues just by looking at plasma constituents had great success: after all, the histological processing of tissues was no longer needed. Even though many authors were alerting that these plasma constituents are often increased even in the absence of any "inflammatory infiltrate", the plasma proteins were so easily accessible that the new direction was not modifiable.
A modern generalization of this type of approach is called "liquid biopsy, " even though it is not limited to the inflammatory states, but to a larger number of identifiable diseases today only histologically.
The effect of the new "molecular" definition of inflammation was that a large number of diseases without significant inflammatory infiltrates (such as obesity, atherosclerosis, aging, dialysis, and chronic kidney disease) are notwithstanding accompanied by the increase of plasma proteins labeled as "inflammatory". Therefore, the list of "inflammatory" diseases (in the new terms) is now much more extensive. The price for such enlargement of conditions is that most new entries do not respond to steroids or other anti-inflammatory drugs.
Conclusion
The new definition of" inflammatory disease" comprises classical steroid-dependent disorders characterized by inflammatory infiltrates and new conditions with minimal inflammatory infiltrates plus the presence of "inflammatory" plasma proteins plus little response to steroids. It might be beneficial to distinguish these types of inflammation.
Significance Damage of the central nervous system (CNS) and neurodegenerative disorders represent the principal cause of morbidity and mortality among adults. An injured CNS is unable to regenerate ...dendritic or neurite connections because they spontaneously occur in the peripheral nervous system. Inhibitory influences of the glial cells and of myelin-associated inhibitors oppose the spontaneous regeneration of CNS neurons. Here, we identify a positive mechanism of neuronal differentiation, which acts in response to activation of intracellular pathway(s) to remove an inhibitory constraint of neurite outgrowth. Unveiling the molecular events regulating the regenerative capacity of neurons will impact on therapeutic initiatives to stem the course of brain damage or neurodegeneration.
Protein kinase A (PKA) controls major aspects of neurite outgrowth and morphogenesis and plays an essential role in synaptic plasticity and memory. However, the molecular mechanism(s) of PKA action on neurite sprouting and activity are still unknown. Here, we report that in response to neurotrophin or cAMP stimulation the RING ligase praja2 ubiquitinates and degrades NOGO-A, a major inhibitor of neurite outgrowth in mammalian brain. Genetic silencing of praja2 severely inhibited neurite extension of differentiating neuroblastoma cells and mesencephalic neurons and axon outgrowth and sprouting of striatal terminals in developing rat brain. This phenotype was rescued when both praja2 and NOGO-A were depleted, suggesting that NOGO-A is, indeed, a biologically relevant target of praja2 in neuronal cells. Our findings unveil a novel mechanism that functionally couples cAMP signaling with the proteolytic turnover of NOGO-A, positively impacting on neurite outgrowth in mammalian brain.
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