| 1. |
- Persson, Patrik, et al.
(författare)
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L-Citrulline, But Not L-Arginine, Prevents Diabetes Mellitus–Induced Glomerular Hyperfiltration and Proteinuria in Rat
- 2014
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Ingår i: Hypertension. - : Lippincott Williams & Wilkins. - 0194-911X .- 1524-4563. ; 64:2, s. 323-329
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Tidskriftsartikel (refereegranskat)abstract
- Diabetes mellitus–induced oxidative stress causes increased renal oxygen consumption and intrarenal tissue hypoxia. Nitric oxide is an important determinant of renal oxygen consumption and electrolyte transport efficiency. The present study investigates whether l-arginine or l-citrulline to promote nitric oxide production prevents the diabetes mellitus–induced kidney dysfunction. Glomerular filtration rate, renal blood flow, in vivo oxygen consumption, tissue oxygen tension, and proteinuria were investigated in control and streptozotocin-diabetic rats with and without chronic l-arginine or l-citrulline treatment for 3 weeks. Untreated and l-arginine–treated diabetic rats displayed increased glomerular filtration rate (2600±162 versus 1599±127 and 2290±171 versus 1739±138 µL/min per kidney), whereas l-citrulline prevented the increase (1227±126 versus 1375±88 µL/min per kidney). Filtration fraction was increased in untreated diabetic rats because of the increase in glomerular filtration rate but not in l-arginine– or l-citrulline–treated diabetic rats. Urinary protein excretion was increased in untreated and l-arginine–treated diabetic rats (142±25 versus 75±7 and 128±7 versus 89±7 µg/min per kidney) but not in diabetic rats administered l-citrulline (67±7 versus 61±5 µg/min per kidney). The diabetes mellitus–induced tissue hypoxia, because of elevated oxygen consumption, was unaltered by any of the treatments. l-citrulline administered to diabetic rats increases plasma l-arginine concentration, which prevents the diabetes mellitus–induced glomerular hyperfiltration, filtration fraction, and proteinuria, possibly by a vascular effect.
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| 2. |
- Nilsson, Linnéa
(författare)
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Studies on the Role of Apoptosis in Kidney Diseases
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Apoptosis is one of the most common types of cell death. Under physiological conditions, it plays an essential role in removal of damaged and potentially harmful cells. Excessive apoptosis has however been linked to a number of diseases including proteinuric kidney disease and DKD, and is believed to enhance the disease progression. Albuminuria and hyperglycemia are common symptoms of these diseases and albumin and high glucose have been seen to trigger intrinsic apoptosis in renal cells. Ouabain, a cardiotonic steroid, has previously been identified as an antiapoptotic agent that in subsaturating concentrations protect from intrinsic apoptosis. The mechanism of the protective effect of ouabain is still not fully understood and it remains to be concluded whether ouabain can protect from albumin and/or glucotoxic-triggered apoptosis.In study I we investigated the protective effects of ouabain in albumin-exposed primary rat PTC and podocytes and in the proteinuric kidney disease animal model passive Heymann nephritis. By reestablishing the balance between the proapoptotic protein BAX and the antiapoptotic protein BCL-XL, ouabain averted the albumin-triggered apoptosis in vitro and in vivo and protected from podocytes loss and glomerular-tubular disconnection.In study II we investigated the relationship between the glucose transporters renal cells express and their susceptibility of glucotoxic-triggered apoptosis. We identified the SGLT expressing cells, PTC and MC, to be more susceptible to high glucose-induced apoptosis than cells without SGLT. The apoptosis was mediated by BAX and BCL-XL imbalance and mitochondrial dysfunction, and was abolished when treated with ouabain or SGLT inhibitors. Podocytes, which lack SGLT, did not respond to short-term high glucose exposure.In study III we used super-resolution microscopy to investigate at which stage of the apoptotic process ouabain start to intervene. Ouabain interfered early in the apoptotic process, where it prevented activation of the sensitizer protein BAD. This allowed BCL-XL to avert BAX activation and translocation to mitochondria and thereby protected from mitochondrial dysfunction and apoptosis.In study IV we investigated differentially expressed genes between renal cortex and primary short-term PTC cultures and between PTC exposed to control and high glucose. The mRNA expression level of most genes was significantly up- or downregulated in PTC compared to renal cortex, with the biggest differences in mitochondria and metabolism related genes. Early state glucotoxicity did not significantly alter mRNA expression levels in PTC.
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| 3. |
- Friederich-Persson, Malou, et al.
(författare)
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Angiotensin II Reduces Transport-Dependent Oxygen Consumption but Increases Transport-Independent Oxygen Consumption in Immortalized Mouse Proximal Tubular Cells
- 2014
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Ingår i: Advances in Experimental Medicine and Biology. - New York, NY : Springer New York. - 0065-2598 .- 2214-8019. - 9781493906208 - 9781493905836 ; 812, s. 157-163
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress is closely associated with renal dysfunction following diabetes and hypertension. Angiotensin II (Ang II) can activate the NADPH-oxidase, increasing oxidative stress that is thought to blunt proximal tubular electrolyte transport and thereby oxygen consumption (QO(2)). We investigated the effect of Ang II on QO(2) in immortalized mouse proximal tubular cells over-expressing the NADPH oxidase subunit p22(phox); a model of increased oxidative stress. Cultured cells were exposed to either Ang II or H2O2 for 48 h. QO(2) was determined during baseline (113 mmol/l NaCl; transport-dependent QO(2)) and during sodium-free conditions (transport-independent QO(2)). Ang II reduced transport-dependent QO(2) in wild-types, but not in p22(phox) which also displayed increased QO(2) at baseline. Transport-independent QO(2) was increased in p22(phox) and Ang II had no additional effect, whereas it increased QO(2) in wild-type. Addition of H2O2 reduced transport-dependent QO(2) in wild-types, but not in p22(phox). Transport-independent QO(2) was unaffected by H2O2. The similar effects of Ang II and H2O2 to reduce transport-dependent QO(2) suggest a direct regulatory role of oxidative stress. In accordance, the transport-dependent QO(2) was reduced in p22(phox) already during baseline. The effects of Ang II on transport-independent QO(2) was not replicated by H2O2, indicating direct regulation via Ang II-receptors independently of oxidative stress. However, the Ang II effect was absent in p22(phox), suggesting that oxidative stress also modulates normal Ang II signaling. In conclusion, Ang II affects both transport-dependent and transport-independent QO(2) in proximal tubular cells and may be an important pathway modulating renal QO(2).
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| 4. |
- Burmakin, Mikhail, et al.
(författare)
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Pharmacological HIF-PHD inhibition reduces renovascular resistance and increases glomerular filtration by stimulating nitric oxide generation
- 2021
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Ingår i: Acta Physiologica. - : John Wiley & Sons. - 1748-1708 .- 1748-1716. ; 233:1
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Hypoxia-inducible factors (HIFs) are O2 -sensitive transcription factors that regulate multiple biological processes which are essential for cellular adaptation to hypoxia. Small molecule inhibitors of HIF-prolyl hydroxylase domain (PHD) dioxygenases (HIF-PHIs) activate HIF-dependent transcriptional programs and have broad clinical potential. HIF-PHIs are currently in global late-stage clinical development for the treatment of anaemia associated with chronic kidney disease. Although the effects of hypoxia on renal haemodynamics and function have been studied in animal models and in humans living at high altitude, the effects of pharmacological HIF activation on renal haemodynamics, O2 metabolism and metabolic efficiency are not well understood.METHODS: Using a cross-sectional study design, we investigated renal haemodynamics, O2 metabolism, gene expression and NO production in healthy rats treated with different doses of HIF-PHIs roxadustat or molidustat compared to vehicle control.RESULTS: Systemic administration of roxadustat or molidustat resulted in a dose-dependent reduction in renovascular resistance (RVR). This was associated with increased glomerular filtration rate (GFR), urine flow and tubular sodium transport rate (TNa ). Although both total O2 delivery and TNa were increased, more O2 was extracted per transported sodium in rats treated with high-doses of HIF-PHIs, suggesting a reduction in metabolic efficiency. Changes in RVR and GFR were associated with increased nitric oxide (NO) generation and substantially suppressed by pharmacological inhibition of NO synthesis.CONCLUSIONS: Our data provide mechanistic insights into dose-dependent effects of short-term pharmacological HIF activation on renal haemodynamics, glomerular filtration and O2 metabolism and identify NO as a major mediator of these effects.
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| 5. |
- Persson, Patrik, et al.
(författare)
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Reduced adenosine A2a receptor–mediated efferent arteriolar vasodilation contributes to diabetes-induced glomerular hyperfiltration
- 2015
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Ingår i: Kidney International. - : Elsevier BV. - 0085-2538 .- 1523-1755. ; 87:1, s. 109-115
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Tidskriftsartikel (refereegranskat)abstract
- Diabetes is associated with increased risk for development of kidney disease, and an increased glomerular filtration rate is an early indication of altered kidney function. Here we determine whether reduced adenosine A2a receptor-mediated vasodilation of the efferent arteriole contributes to the increased glomerular filtration rate in diabetes. The glomerular filtration rate, renal blood flow, and proximal tubular stop flow pressure were investigated in control and streptozotocin-diabetic rats during baseline and after administration of the adenosine A2a receptor antagonist ZM241385 or the adenosine A2a receptor agonist CGS21680. The diabetes-induced glomerular hyperfiltration was reduced by 24% following A2a receptor stimulation but was unaffected by A2a receptor inhibition. Contrarily, glomerular filtration rate in controls increased by 22% after A2a receptor inhibition and was unaffected by A2a stimulation. The increased glomerular filtration rate after A2a receptor inhibition in controls and decreased glomerular filtration rate after A2a receptor activation in diabetics were caused by increased and decreased stop flow pressure, respectively. None of the interventions affected renal blood flow. Thus, the normal adenosine A2a receptor-mediated tonic vasodilation of efferent arterioles is abolished in the diabetic kidney. This causes increased efferent arteriolar resistance resulting in increased filtration fraction and hyperfiltration.
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| 6. |
- Sivertsson, Ebba, et al.
(författare)
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Lowering plasma levels of protein-bound uremic toxins improves cardiac output and renal oxygenation in a rat model of chronic kidney disease
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Chronic kidney disease (CKD) is an increasing health problem which is closely associated with cardiac dysfunction. In CKD uremic toxins accumulate as kidney function declines. Indoxyl sulfate is a uremic toxin that induces kidney tissue hypoxia, proteinuria and kidney damage. Furthermore, high salt intake is a growing health issue worldwide. In this study, we investigated the effect of reducing plasma indoxyl sulfate in a rat model of CKD challenged with high salt intake and compared the effects to that of conventional treatment using an angiotensin converting enzyme inhibitor (ACEI). In rats, the right kidney and 2/3 of the left kidney were surgically removed (5/6 nephrectomy). Animals were fed a normal salt containing diet for four weeks and randomized to either vehicle or chronic treatment with either the oral absorbent AST-120 or the ACEI enalapril. Thereafter, kidney function was measured before and after a week of high salt intake. Cardiac output was measured at the end of the study period. A reduction of plasma levels of indoxyl sulfate by AST-120 improved cardiac output as well as urinary oxidative stress and proteinuria. ACEI reduced oxidative stress in kidney tissue and significantly improved proteinuria and the glomerular filtration rate in response to the high salt intake. Both interventions improved intrarenal oxygen availability.In conclusion, decreasing circulating levels of protein bound uremic toxins, e.g. indoxyl sulfate, improves cardiac output, reduces urinary oxidative stress and proteinuria in experimental CKD. Reduced angiotensin II signaling has direct reno-protective effects by decreasing intrarenal oxidative stress, protecting renal reserve and increasing urinary Na+ excretion during high salt intake. Both treatments had striking effects on cortical oxygen availability. A dual strategy, to reduce indoxyl sulfate and angiotensin II signaling simultaneously, could be an efficient strategy to target both cardiac and renal dysfunction in CKD, to further slow progression of disease.
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| 7. |
- Sivertsson, Ebba, 1984-
(författare)
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Oxygen Metabolism in Experimental Kidney Disease
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tubulointerstitial hypoxia has been proposed a unifying mechanism behind the development of chronic kidney disease (CKD), regardless of primary diagnosis. Important factors that contribute to the development of hypoxia are reduced bioavailability of nitric oxide (NO), oxidative stress and mitochondria uncoupling. Diabetes and hypertension are the leading causes of CKD. Once established, CKD is a progressive disease and there is no curative treatment. This thesis aimed to investigate the in vivo kidney oxygen metabolism and in vitro mitochondria function in animal models of pathological conditions known to cause kidney injury.The immunosuppressant drug rapamycin has been suggested to counteract diabetic nephropathy by reducing kidney hypertrophy and proteinuria. In a rat model of diabetes type 1, we demonstrate that rapamycin induced intrarenal hypoxia, oxidative stress and mitochondria leak respiration. In diabetic animals, these changes, together with diabetes induced tubular injury, were further aggravated by rapamycin. Proteinuria was decreased by rapamycin in diabetic animals, due to altered glomerular permeability of large molecules. When investigating the role of hypoxia in development of nephropathy there are often confounding factors such as concomitant hyperglycemia, hypertension and oxidative stress to consider. In rats, we demonstrate that increased kidney metabolism, induced by increased thyroid hormone signaling, induced kidney hypoxia, proteinuria and mitochondria leak respiration. Importantly blood glucose, blood pressure and oxidative stress was unchanged. This provides further evidence that hypoxia per se can induce kidney injury. The role of mitochondria dysfunction in hypertensive kidney disease is unclear and angiotensin II (Ang II) has been shown to inhibit mitochondria respiration. In a mouse model of hypertension, we demonstrate that Ang II regulation of mitochondria respiration was dose-dependent. Low Ang II signaling increased leak respiration without compromising efficiency of oxidative phosphorylation. In contrast, high Ang II signaling inhibited mitochondria respiration and decreased efficiency of oxidative phosphorylation. Finally, uremic toxins accumulate in patients with CKD and correlate with the degree of decline in kidney function. In a rat model of CKD, we demonstrate that treatment to reduce plasma levels of protein bound uremic toxins improves cardiac output and kidney oxygenation. In summary, the common denominator for pathological conditions investigated in this thesis is the occurrence of intrarenal hypoxia. This thesis demonstrates that increased mitochondria oxygen consumption via leak respiration as an important contributing factor. Further, targeting plasma levels of circulating uremic toxins may be a potential treatment strategy to slow the rate of progression of CKD.
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| 8. |
- Sivertsson, Ebba, 1984-, et al.
(författare)
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Thyroid hormone increases oxygen metabolism causing intrarenal tissue hypoxia; a pathway to kidney disease
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The proposed mechanisms for the development of nephropathy are many, complex and often overlapping. Although recent literature strongly supports a role of kidney hypoxia as an independent pathway to nephropathy, the evidence remains inconclusive since the role of hypoxia is difficult to differentiate from confounding factors such as hyperglycemia, hypertension and oxidative stress. By increasing kidney oxygen consumption using triiodothyronine (T3) and, thus, avoiding these confounding factors, the aim of the present study was to investigate renal hypoxia per se as a causal pathway for the development of nephropathy.Healthy Sprague-Dawley rats were treated with T3 (10 µg/kg/day) and the angiotensin II AT1-receptor antagonist candesartan (1 mg/kg in drinking water) to eliminate effects of T3-induced renin release for 7 weeks after which in vivo kidney function, oxygen metabolism and mitochondrial function were evaluated.T3 did not affect glomerular filtration rate or renal blood flow, but increased total kidney oxygen consumption resulting in cortical hypoxia. Nephropathy, demonstrated as proteinuria and albuminuria developed in T3-treated animals. Mitochondria uncoupling mediated by uncoupling protein 2 and the adenosine nucleotide transporter was demonstrated as a mechanism causing the increased kidney oxygen consumption. Importantly, blood glucose levels, mean arterial blood pressure and oxidative stress levels were not affected by T3. In conclusion, the present study provides further evidence for increased kidney oxygen consumption causing intrarenal tissue hypoxia, as a causal pathway for development of nephropathy.
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| 9. |
- Franzen, Stephanie, et al.
(författare)
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Differences in susceptibility to develop parameters of diabetic nephropathy in four mouse strains with type 1 diabetes
- 2014
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1931-857X .- 1522-1466. ; 306:10, s. F1171-F1178
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Tidskriftsartikel (refereegranskat)abstract
- One-third of diabetes mellitus patients develop diabetic nephropathy, and with underlying mechanisms unknown it is imperative that diabetic animal models resemble human disease. The present study investigated the susceptibility to develop diabetic nephropathy in four commonly used and commercially available mouse strains with type 1 diabetes to determine the suitability of each strain. Type 1 diabetes was induced in C57Bl/6, NMRI, BALB/c, and 129Sv mice by alloxan, and conscious glomerular filtration rate, proteinuria, and oxidative stress levels were measured in control and diabetic animals at baseline and after 5 and 10 wk. Histological alterations were analyzed using periodic acid-Schiff staining. Diabetic C57Bl/6 displayed increased glomerular filtration rate, i.e., hyperfiltration, whereas all other parameters remained unchanged. Diabetic NMRI developed the most pronounced hyperfiltration as well as increased oxidative stress and proteinuria but without glomerular damage. Diabetic BALB/c did not develop hyperfiltration but presented with pronounced proteinuria, increased oxidative stress, and glomerular damage. Diabetic 129Sv displayed proteinuria and increased oxidative stress without glomerular hyperfiltration or damage. However, all strains displayed intras-train correlation between oxidative stress and proteinuria. In conclusion, diabetic C57Bl/6 and NMRI both developed glomerular hyperfiltration but neither presented with histological damage, although NMRI developed low-degree proteinuria. Thus these strains may be suitable when investigating the mechanism causing hyperfiltration. Neither BALB/c nor 129Sv developed hyperfiltration although both developed pronounced proteinuria. However, only BALB/c developed detectable histological damage. Thus BALB/c may be suitable when studying the roles of proteinuria and histological alterations for the progression of diabetic nephropathy.
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| 10. |
- Franzen, Stephanie, et al.
(författare)
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Repetitive Measurements of Intrarenal Oxygenation In Vivo Using L Band Electron Paramagnetic Resonance
- 2014
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Ingår i: Advances in Experimental Medicine and Biology. - New York, NY : Springer New York. - 0065-2598 .- 2214-8019. - 9781493906208 - 9781493905836 ; 812, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- Intrarenal oxygenation is heterogeneous with oxygen levels normally being highest in the superficial cortex and lowest in the inner medulla. Reduced intrarenal oxygenation has been implied in the pathology of several kidney diseases. However, there is currently no method available to repetitively monitor regional renal oxygenation using minimally invasive procedures. We therefore evaluated implantable lithium phthalocyanine (LiPc) probes, which display a close correlation between EPR line width and oxygen availability. LiPc probes were implanted in the kidney cortex and medulla in the same mouse and sEPR spectra were acquired using a L band scanner during inhalation of air (21 % oxygen) or a mixture of air and nitrogen (10 % oxygen). In order to separate the signals from the two probes, a 1 G/cm gradient was applied and the signals were derived from 40 consecutive sweeps. Peak-to-peak comparison of the EPR line was used to convert the signal to an approximate oxygen tension in MATLAB. Kidney cortex as well as medullary oxygenation was stable over the 45 day period (cortex 56 +/- 7 mmHg and medulla 43 +/- 6 mmHg). However, 10 % oxygen inhalation significantly reduced oxygenation in both cortex (56 +/- 6 to 34 +/- 2 mmHg n = 15 p < 0.05) and medulla (42 +/- 5 to 29 +/- 3 mmHg n = 7 p < 0.05). In conclusion, L band EPR using LiPc probes implanted in discrete intrarenal structures can be used to repetitively monitor regional renal oxygenation. This minimally invasive method is especially well suited for conditions of reduced intrarenal oxygenation since this increases the signal intensity which facilitates the quantification of the EPR signal to absolute oxygenation values.
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