Burden of disease assessment for Germany and its regions – results from the BURDEN 2020 study

Background

Epidemiological measures such as incidence, prevalence, or deaths are essential for monitoring population health. However, evaluating them in isolation cannot adequately compare and assess the relative importance of different diseases. Assessments of the burden of disease (BoD) are therefore of growing importance in supporting health policy decisions. Using disability-adjusted life years (DALY) as a summary measure of population health, BoD integrates morbidity and mortality in a transparent approach.

Methods

Within BoD methodology, deviations in the health of the population from an ‘ideal’ health status is quantified in the unit of life years. DALY are the sum of years of life lost due to death (YLL) and years lived with disability (YLD). While YLL describe the gap between age at death and statistical life expectancy, the indicator YLD quantifies years lived with a disability or disease. Calculations were based on different primary and secondary data sources for Germany, especially cause-of-death statistics, epidemiological survey data, and statutory health insurance data.

Results

In Germany, there were about 12 million DALY in 2017, the equivalent of 14,584 DALY per 100,000 population. Coronary heart disease contributes the most to the overall burden of disease, followed by lower back pain and lung cancer. In women, headache disorders and dementias account for more DALY as compared to men. Men have a higher burden of disease from lung cancer or alcohol use disorders. Pain disorders and alcohol use disorders lead the DALY rankings for both sexes in younger adulthood. The burden due to cardiovascular disease, COPD, and diabetes mellitus increases with age and also varies by region.

Conclusions

The results suggest age- and gender-specific prevention as well as regional health care needs. BoD studies therefore provide comprehensive data for population health surveillance and can support health policy decisions.

Key messages

• The importance of specific diseases as measured by DALY differs greatly by age and gender, highlighting the need for targeted prevention measures.

• Regional patterns emerge for cardiovascular disease, COPD, and depressive disorders, among others, which may indicate health care needs.

Regional differences in the attributable burden for Germany: Exploring YLL for selected risk factors

Background

Within the BURDEN 2020 project (Burden of disease in Germany at the national and sub-national level) we calculate burden of disease indicators on a small-scale level for Germany. In order to provide a comprehensive view over diseases and their impact on population health, Years of Life Lost due to premature death (YLL) and Years Lived with Disability (YLD) are summed up to the measure Disability Adjusted Live Years (DALY). YLL, YLD and DALY will be attributed to a set of risk factors.

Methods

Object of the analysis is the indicator YLL across spatial planning regions in Germany. It is calculated by multiplying the number of deaths with the remaining life expectancy at the age of deaths. A share of YLL can be attributed to specific risk factors. Smoking and ambient particulate matter pollution are used as examples. The distribution of risk factors is based on German health surveys and local air pollution measurements. The analysis follows the Comparative Risk Assessment approach, which quantifies the possible change in burden by assuming a different exposure level in the past.

Results

Based on the absolute YLL estimates, the overall leading causes of deaths are ischemic heart diseases, tracheal, bronchus, and lung cancer and stroke. In addition, for women breast cancer is a leading cause of death. Causes vary by age groups and by region. We expect the attributable fraction to vary across local areas as well.

Conclusions

When it comes to health care intervention, the method of attributing risk factors to burden of disease outcomes reveals necessary fields of action, especially across regions. In order to allocate financial resources within the health care, the CRA can provide additional arguments for political decision making.

Key messages

Causes of death and the related years of life lost are an integral part of health monitoring. Our analysis reveals how YLL and risk factor attributable burden vary across German regions.

A promoter polymorphism of the alpha 8 integrin gene and the progression of autosomal-dominant polycystic kidney disease

BACKGROUND/AIMS

Dysregulation of integrins is a feature of tissue remodeling in autosomal-dominant polycystic kidney disease (ADPKD). The alpha 8 beta 1 integrin (alpha8beta1) affects kidney development and the susceptibility to renal injury in mice. We investigated whether the -414 T/C polymorphism in the promoter region of the alpha 8 integrin chain gene (ITGA8) is associated with the progression of renal disease in ADPKD.

METHODS

Genotyping for the -414 T/C polymorphism was performed by allelic separation using RT-PCR in 294 patients with ADPKD. Alpha 8 integrin expression was detected by RT-PCR and immunohistochemistry.

RESULTS

41% of the study population reached end stage renal disease at a mean age of 51 +/- 12 years. The frequency of the -414 C allele was 0.194 in ADPKD. C allele carriers (CC and TC genotypes) were compared with patients homozygous for the T allele (TT genotype). Kaplan-Meier analysis revealed that end-stage renal failure occurred at a significantly younger age in TT homozygotes (median age, 47 years; 95% CI, 46-49 years) than in C allele carriers (median age, 51 years; 95% CI, 49-53 years; p = 0.046 by the log-rank test). When parameters of ADPKD patients were compared between genotype by analysis of variance, only age at onset of end-stage renal failure was significantly different (p = 0.026) whereas age at onset of hypertension, body surface area, 24-hour systolic and diastolic blood pressure did not differ. In kidneys of ADPKD, expression of alpha 8 integrin is increased and found de novo in cystic epithelia.

CONCLUSION

A polymorphism of the ITGA8 promoter modifies the progression of renal failure in ADPKD.

Aldosterone responsiveness of the epithelial sodium channel (ENaC) in colon is increased in a mouse model for Liddle's syndrome

Liddle's syndrome is an autosomal dominant form of human hypertension, caused by gain-of-function mutations of the epithelial sodium channel (ENaC) which is expressed in aldosterone target tissues including the distal colon. We used a mouse model for Liddle's syndrome to investigate ENaC-mediated Na+ transport in late distal colon by measuring the amiloride-sensitive transepithelial short circuit current (Delta I SC-Ami) ex vivo. In Liddle mice maintained on a standard salt diet, Delta I SC-Ami was only slightly increased but plasma aldosterone (P Aldo) was severely suppressed. Liddle mice responded to a low or a high salt diet by increasing or decreasing, respectively, their P Aldo and Delta I SC-Ami. However, less aldosterone was required in Liddle animals to achieve similar or even higher Na+ transport rates than wild-type animals. Indeed, the ability of aldosterone to stimulate Delta I SC-Ami was about threefold higher in Liddle animals than in the wild-type controls. Application of aldosterone to colon tissue in vitro confirmed that ENaC stimulation by aldosterone was not only preserved but enhanced in Liddle mice. Aldosterone-induced transcriptional up-regulation of the channel's beta- and gamma-subunit (beta ENaC and gamma ENaC) and of the serum- and glucocorticoid-inducible kinase 1 (SGK1) was similar in colon tissue from Liddle and wild-type animals, while aldosterone had no transcriptional effect on the alpha-subunit (alpha ENaC). Moreover, Na+ feedback regulation was largely preserved in colon tissue of Liddle animals. In conclusion, we have demonstrated that in the colon of Liddle mice, ENaC-mediated Na+ transport is enhanced with an increased responsiveness to aldosterone. This may be pathophysiologically relevant in patients with Liddle's syndrome, in particular on a high salt diet, when suppression of P Aldo is likely to be insufficient to reduce Na+ absorption to an appropriate level.

Role of fibrillin-1 in hypertensive and diabetic glomerular disease

The microfibrillar protein fibrillin-1 is a component of the mesangial matrix. Defects in fibrillin-1 predisposes individuals to vascular damage in Marfan syndrome, but the role of fibrillin-1 in kidney disease is unknown. We hypothesized that fibrillin-1 is involved in hypertensive or diabetic glomerular disease. DOCA-salt hypertension or streptozotocin (STZ) diabetes led to a significant increase in glomerular fibrillin-1 deposition. To test the functional role of fibrillin-1, DOCA hypertension and STZ diabetes were induced in mice homozygous for a mutation leading to a fivefold lower expression of fibrillin-1 (mgR/mgR). Untreated male mgR/mgR mice usually die from aortic dissection during the first 4 mo of life. All DOCA-treated mgR/mgR mice died within 2 wk after onset of DOCA treatment. DOCA-treated heterozygous (mgR/+) and their wild-type littermates displayed similar blood pressure levels, but albuminuria was significantly lower in mgR/+ than in wild-type mice after DOCA treatment. Similarly, STZ diabetic mgR/mgR and mgR/+ developed lower albuminuria than wild-type mice despite higher blood glucose levels in mgR/mgR and mgR/+ compared with wild-type mice. Blood pressure, blood glucose, and albuminuria did not differ among untreated mgR/mgR, mgR/+, and wild-type mice, respectively. In diabetic mgR/+ and mgR/mgR, but not in wild-type mice, an induction of glomerular decorin expression was observed. Thus underexpression of fibrillin-1 predisposes individuals to lethal aortic dissection in the presence of hypertension. On the other hand, albuminuria as a parameter of microvascular damage in hypertension and diabetes was ameliorated in fibrillin-1-underexpressing mice, possibly due to a compensatory upregulation of decorin. We conclude that fibrillin-1 may contribute to glomerular damage in hypertensive and diabetic kidney disease.

Subtotal nephrectomy impairs ischemia-induced angiogenesis and hindlimb re-perfusion in rats

Kidney disease is associated with increased cardiovascular morbidity, but underlying mechanisms are poorly understood. We tested the hypothesis that chronic renal insufficiency impairs angioadaptation in a rat model of hindlimb ischemia. Twenty male Sprague-Dawley rats (8 weeks old) underwent subtotal nephrectomy (5/6SNX) or sham surgery (each n=10). Ten weeks later, unilateral hindlimb ischemia was induced in all animals. Hindlimb perfusion was assessed by laser Doppler perfusion imaging and fluorescent microsphere injection studies 2 weeks after surgery. Ischemia-induced angiogenesis was measured by analyzing capillary density using CD31 immunofluorescence. Expression of vascular endothelial growth factor (VEGF), its receptors (VEGFRs) and inducible as well as endothelial nitric oxide (NO) synthase was measured by real-time reverse transcription-polymerase chain reaction. Laser Doppler hindpaw perfusion was significantly reduced in 5/6SNX compared to sham-operated animals. Impaired hindlimb re-perfusion in 5/6SNX vs control rats was confirmed by fluorescent microsphere injection studies (relative perfusion of ischemic vs non-ischemic limb: 68.9+/-6.4 vs 92.4+/-3.6%, P=0.005). Ischemic skeletal muscle neovascularization increased to a greater extent in sham-operated compared to 5/6SNX rats (69+/-8 vs 29+/-7%, P<0.05). VEGF and VEGFR-1/2 mRNA expression increased in ischemic hindlimbs of control rats, whereas no change or a decrease was observed in 5/6SNX. In contrast, inducible and endothelial NO synthase expression did not significantly differ between sham and 5/6SNX rats. Chronic renal insufficiency impairs angiogenesis and limb perfusion in a rat hindlimb ischemia model. Impaired angioadaptation may contribute to the poor prognosis of patients with renal failure suffering from peripheral arterial disease.

Angiotensin II formation in the kidney and nephrosclerosis in Ren-2 hypertensive rats

BACKGROUND

Ren-2 transgenic hypertensive rats develop malignant hypertensive nephrosclerosis despite low to normal plasma angiotensin II and suppressed renal renin. We tested the hypothesis that local angiotensin II formation occurs at sites of renal vascular and interstitial injury in this model.

METHODS

Heterozygous Ren-2 transgenic rats were compared with normotensive Sprague-Dawley-Hannover control rats and Ren-2 transgenic rats treated with a very low dose of an angiotensin II type 1 (AT1) receptor antagonist, 1 mg/kg/day losartan, for 4 weeks. Blood pressure measurements, quantifications of urinary albumin, plasma and tissue angiotensin II as well as immunohistochemical analyses were performed.

RESULTS

Systolic blood pressure was not affected by losartan during the study but intra-arterial recordings revealed a decrease of blood pressure. Losartan reduced albumin excretion, cell proliferation, macrophage influx, collagen I and collagen IV deposition. Plasma angiotensin II was decreased, while kidney tissue angiotensin II content was increased in Ren-2 transgenic rats compared with control rats. In Ren-2 transgenic rats, juxtaglomerular renin and angiotensin II staining were reduced, but there was a marked angiotensin II staining at foci of tubulo-interstitial fibrosis and at proliferative malignant vascular lesions.

CONCLUSION

We conclude that local angiotensin II formation is increased in proliferative or fibrotic kidney lesions in the Ren-2 transgenic rat. Local angiotensin II formation may help to explain why the AT1 receptor antagonist prevents or ameliorates this transgenic model of malignant nephrosclerosis despite low to normal plasma angiotensin II and suppressed renal renin.

Fibrillin-1 regulates mesangial cell attachment, spreading, migration and proliferation

The microfibrillar protein fibrillin-1 is present in many organs, including the vasculature, eye, and dermis, and is thought to convey structural anchorage and elastic strength. Fibrillin-1 is also a component of the mesangial matrix. To assess the functional relevance of fibrillin-1 for cell-matrix interactions in the glomerulus, we studied the attachment, spreading, migration and proliferation of mesangial cells on fibrillin-1 and the regulation of fibrillin-1 in experimental anti-Thy1.1 nephritis displaying mesangial cell migration and proliferation in vivo. During the acute phase of experimental Thy1.1 nephritis, glomerular fibrillin-1 messenger ribonucleic acid expression and protein immunoreactivity were significantly induced as compared to controls. In a hexosaminidase-based adhesion assay, mesangial cells showed concentration-dependent attachment to fibrillin-1, similar to what was observed for fibronectin. The cell attachment was Arg-Gly-Asp dependent. Further, fibrillin-1 significantly promoted spreading and focal contact formation detected by immunostaining for vinculin. Mesangial cell migration, assessed by a transmigration assay, and proliferation, measured by a 5-bromo-2'-deoxy-uridine incorporation assay, were augmented by fibrillin-1. In diabetic mice underexpressing fibrillin-1, glomerular cell proliferation, determined by counting proliferating cell nuclear antigen-positive cells in renal sections, was significantly lower than in diabetic control mice. We conclude that fibrillin-1 promotes mesangial cell attachment, spreading, migration, and proliferation. We speculate that fibrillin-1 may thus contribute to mesangial hypercellularity during glomerular disease.

Adrenomedullin reduces mesangial cell number and glomerular inflammation in experimental mesangioproliferative glomerulonephritis

BACKGROUND

Adrenomedullin (ADM) is a vasodilator peptide that is abundantly expressed in the kidney. ADM has antiproliferative effects on glomerular mesangial cells (MC) in vitro. Whether or not treatment with ADM can reduce MC proliferation in vivo [i.e., in mesangioproliferative glomerulonephritis (GN)] is unknown. We tested the hypothesis that ADM substitution reduces MC proliferation in GN.

METHODS

GN in rats was induced by injection of an anti-Thy-1.1 antibody. Rats received osmotic minipumps, which continuously delivered rat ADM (500 ng/hour, N = 11), or vehicle (N = 13) from day 3 to day 6 after GN induction. Rats were sacrificed 6 days after induction of GN. On kidney sections, cells staining positive for proliferating cell nuclear antigen, mesangial cells, monocytes, and apoptotic cells were counted. Parameters of inflammation and fibrosis were measured in renal cortex and sieved glomeruli by real-time polymerase chain reaction (PCR).

RESULTS

Systolic blood pressure, diuresis, albuminuria, creatinine clearance, microaneurysm formation, and mesangial matrix expansion were not influenced by ADM infusion. However, ADM treatment significantly reduced the number of MC, showed a tendency to reduce total glomerular cell proliferation, and significantly increased apoptosis. ADM-treated GN animals showed significantly less glomerular monocyte infiltration. ADM treatment normalized transforming growth factor (TGF)-beta1 mRNA expression and reduced monocyte chemoattractant protein-1 (MCP-1), osteopontin, plasminogen activator inhibitor-1 (PAI-1), collagen I, and collagen III mRNA expression significantly.

CONCLUSION

Exogenous ADM infusion reduces MC number and glomerular monocyte infiltration in the state of mesangial proliferation during acute experimental mesangioproliferative GN. These findings indicate that ADM can influence the course of mesangioproliferative GN.

Induction and coexpression of latent transforming growth factor beta-binding protein-1 and fibrillin-1 in experimental glomerulonephritis

BACKGROUND

Latent transforming growth factor-beta-binding protein 1 (LTBP-1) and fibrillin-1 were shown to colocalize and interact in the extracellular matrix of the skin and vasculature. This interaction may regulate transforming growth factor-beta (TGF-beta) activity. TGF-beta is an important progression factor for glomerular diseases. We hypothesized that LTBP-1 and fibrillin-1 are coexpressed in the glomerulus and upregulated during glomerulonephritis.

METHODS

Acute anti-Thy1.1 glomerulonephritis was induced with a single intravenous injection (1 mg/kg body weight) of a monoclonal anti-Thy1.1 antibody in rats. Real-time RT-PCR and immunohistochemical analyses for LTBP-1 and fibrillin-1 were performed.

RESULTS

Induction of glomerular LTBP-1 mRNA was detected on day 2 of disease, while mRNA for fibrillin-1 was already upregulated 1 day after induction of disease. Both LTBP-1 and fibrillin-1 showed a mesangial distribution. An expansion of the LTBP-1 and fibrillin-1-positive mesangial area was seen on day 6 of disease, when transient matrix accumulation was most prominent. On day 12 of disease, glomerular LTBP-1 and fibrillin-1 immunoreactivities had returned to control levels. In serial sections, some colocalization of LTBP-1 and fibrillin-1 was detected in control as well as in nephritic glomeruli.

CONCLUSION

Mesangial expression of LTBP-1 and fibrillin-1 is induced early in experimental nephritis and LTBP-1 and fibrillin-1 are partially colocalized in the nephritic glomerulus. An interaction of these molecules could stabilize latent TGF-beta complexes and thus attenuate the activation of TGF-beta during this self-limited glomerular disease.

Effects of sympathetic nerves and angiotensin II on renal sodium and water handling in rats with common bile duct ligature

We tested the hypothesis that angiotensin II is likely to be mandatory for the neurogenic sodium and volume retention in cirrhotic rats with common bile duct ligature (BDL) following an acute volume load. To assess the neural control of volume homeostasis, 21 days after common BDL rats underwent volume expansion (0.9% NaCL; 10% body wt over 30 min) to decrease renal sympathetic nerve activity. Untreated animals, rats with renal denervation or pretreated with a nonhypotensive dose of an angiotensin II type 1 receptor antagonist were studied. The renal renin-angiotensin system was assessed by immunohistochemistry and RT-PCR. Rats with BDL excreted only 71 ± 4% of the administered volume load. In cirrhotic rats pretreated with an angiotensin II AT1inhibitor or after renal denervation, these values ranged significantly higher from 98 to 103% ( P < 0.05 for all comparisons). Renal sympathetic nerve activity decreases by volume expansion were impaired in BDL rats ( P < 0.05) but unaffected by angiotensin II receptor inhibition. In kidneys of BDL animals, renin mRNA was increased, and immunohistochemistry revealed increased staining for peritubular angiotensin II. Renal denervation in BDL animals reduced renin expression within 5 days to control levels. In conclusion, the impaired excretion of an acute volume load in rats with liver cirrhosis is due to effects of an increased renal sympathetic nerve activity that are likely to be dependent on intrarenal angiotensin II and renin. We speculate that similar changes may contribute to long-term volume retention in liver cirrhosis.

Glycosaminoglycan polymerization may enable osmotically inactive Na+ storage in the skin

Osmotically inactive skin Na(+) storage is characterized by Na(+) accumulation without water accumulation in the skin. Negatively charged glycosaminoglycans (GAGs) may be important in skin Na(+) storage. We investigated changes in skin GAG content and key enzymes of GAG chain polymerization during osmotically inactive skin Na(+) storage. Female Sprague-Dawley rats were fed a 0.1% or 8% NaCl diet for 8 wk. Skin GAG content was measured by Western blot analysis. mRNA content of key dermatan sulfate polymerization enzymes was measured by real-time PCR. The Na(+) concentration in skin was determined by dry ashing. Skin Na(+) concentration during osmotically inactive Na(+) storage was 180-190 mmol/l. Increasing skin Na(+) coincided with increasing GAG content in cartilage and skin. Dietary NaCl loading coincided with increased chondroitin synthase mRNA content in the skin, whereas xylosyl transferase, biglycan, and decorin content were unchanged. We conclude that osmotically inactive skin Na(+) storage is an active process characterized by an increased GAG content in the reservoir tissue. Inhibition or disinhibition of GAG chain polymerization may regulate osmotically inactive Na(+) storage.

Induction of connective tissue growth factor by angiotensin II: integration of signaling pathways

OBJECTIVE

Angiotensin II is recognized as one of the major mediators of cardiovascular pathology. Because connective tissue growth factor (CTGF) is involved in the pathophysiologic processes underlying fibrotic diseases, its regulation by angiotensin II was investigated.

METHODS AND RESULTS

In the 2-kidney, 1-clip model of renovascular hypertension, increased expression of CTGF was detectable in the hypertrophic left ventricle. By activation of angiotensin II type 1 receptors, angiotensin II caused rapid expression of CTGF mRNA and protein in a human fibroblast cell line. Activation of the p42/44 mitogen-activated protein (MAP) kinase signaling pathway proved to be essential for angiotensin II-stimulated CTGF expression. Inhibition of MAP kinase activation by forskolin prevented CTGF induction. Inhibition of the isoprenylation of small GTPases by simvastatin or pretreatment of the cells with toxin B reduced basal CTGF expression below detection limits and prevented induction by angiotensin II. Specific interference with RhoA signaling by Y27632 primarily reduced basal CTGF expression. There was no significant reduction of expression of angiotensin II type 1 receptors by simvastatin. These data indicate cooperation between the Rho signaling and the angiotensin II-activated MAP kinase pathways.

CONCLUSIONS

Direct induction of CTGF by angiotensin II is indicative of a role for CTGF in angiotensin II-mediated fibrosis and might be a target of antifibrotic interventions.

Angiotensin II type 1 receptor blockade prevents lethal malignant hypertension: relation to kidney inflammation

BACKGROUND

Angiotensin II is elevated in malignant hypertension. We tested the hypothesis that angiotensin II type 1 receptor blockade can prevent the development of malignant hypertension even in the absence of a blood pressure-lowering effect.

METHODS AND RESULTS

Two-kidney, 1-clip rats were followed up for 28 days; blood pressure was measured by tail-cuff plethysmography and intra-arterially. After a 2-week run-in phase, rats received valsartan at a dose of 0.3 (n=14) or 3 (n=12) mg. kg(-1). d(-1) or solvent (n=27). Only the higher dose of valsartan, but not the lower dose, decreased blood pressure. Both doses of valsartan prevented the development of lethal malignant hypertension. Twenty of 27 solvent-treated renovascular hypertensive rats died, but only 3 of 14 rats treated with the low dose and 1 of 12 rats treated with the high dose of valsartan died. Histological signs of malignant nephrosclerosis were found in all rats examined that had died throughout the study and in 6 of 7 surviving solvent-treated renovascular hypertensive animals. Increased expression of monocyte chemoattractant protein-1 and prominent interstitial influx of macrophages occurred in the nonclipped kidneys exposed to high pressure in solvent-treated rats. These alterations were prevented by valsartan at both doses, irrespective of blood pressure effects.

CONCLUSIONS

Angiotensin II type 1 receptor blockade by valsartan prevents lethal malignant hypertension independently of blood pressure. The results suggest that reduction of angiotensin-induced inflammation in the kidney may contribute to the protective effects of valsartan.

Inducible nitric oxide synthase and glomerular hemodynamics in rats with liver cirrhosis

This study was designed to test the hypothesis that glomerular de novo expression of inducible nitric oxide synthase (iNOS) contributes to renal hemodynamic abnormalities in liver cirrhosis developed 3 wk after common bile duct ligature (CBDL). De novo expression of iNOS mRNA was detected by RT-PCR in RNA extracts from isolated CBDL rat glomeruli whereas no iNOS mRNA was found in control rat glomerular RNA. Immunohistochemical staining for iNOS was negative in control animals whereas, in CBDL rats, positive iNOS staining was detected in an apparently mesangial pattern in all glomeruli. Western blots of protein extracts from isolated glomeruli of CBDL rats, but not control animals, showed a prominent iNOS band of 130 kDa. Mean arterial pressure (MAP), renal plasma flow (RPF; p-aminohippurate clearance), and glomerular filtration rate (GFR; inulin clearance) were unaltered in CBDL rats, but the application of 4 mg/kg L-N(6)-(1-iminoethyl)lysine, a specific inhibitor of iNOS, reduced GFR and RPF significantly in CBDL rats, whereas control animals were not affected. Similar results were obtained with lipopolysaccharide (LPS)-pretreated animals, which were studied as a positive control for iNOS expression and as a model for recent iNOS induction. We conclude that de novo expression of iNOS occurs in glomeruli of rats with liver cirrhosis and that nitric oxide, generated by iNOS, contributes to the maintenance of glomerular filtration in the early state of this disease.

Glomerular osteopontin expression and macrophage infiltration in glomerulosclerosis of DOCA-salt rats

Expression of the chemoattractant osteopontin (OPN) may contribute to macrophage infiltration in many types of tubulointerstitial kidney disease, but the role of OPN in chronic glomerulosclerosis is unknown. We hypothesized that glomerular OPN expression and macrophage infiltration occur in deoxycorticosterone acetate (DOCA)-salt glomerulosclerosis in rats. Uninephrectomized rats receiving DOCA pellets and 1% saline were compared with control rats. OPN mRNA was determined by Northern blot, and OPN protein was determined by Western blot. The localization of OPN was studied by in situ hybridization and double immunohistochemistry with glomerular cell markers. Macrophage infiltration was quantified by counting ED-1-positive cells, and semiquantitative glomerulosclerosis scores were obtained. In DOCA-salt rats, OPN mRNA in the kidney was increased 2-fold over control after 9 days and 3 weeks and 20-fold after 6 weeks. Tubulointerstitial OPN staining was apparent after 21 days of DOCA treatment. Glomerular OPN mRNA and protein was detected after 42 days in parietal and visceral epithelial cells, activated myofibroblasts, and occasionally mesangial cells. Progressive glomerular macrophage infiltration occurred during the development of DOCA hypertension, paralleling the degree of glomerulosclerosis. Glomeruli staining positive for osteopontin contained more macrophages (18.4 +/- 3.4 per cross-section) than osteopontin-negative glomeruli (3.6 +/- 0.5; P < 0.05). Glomerular OPN expression occurs in chronic hypertensive glomerulosclerosis and is associated with macrophage infiltration. The data suggest a role for OPN as a chemoattractant in hypertensive glomerulosclerosis.

Photosynthetic performance of the Atlantic brown macroalgae, Cystoseira abies-marina, Dictyota dichotoma and Sargassum vulgare, measured in Gran Canaria on site

Photosynthetic performance was determined in three common Atlantic brown macroalgae, Cystoseira abies-marina, Dictyota dichotoma and Sargassum vulgare, in Gran Canaria, Canary Islands, on site. The photosynthetic quantum yield was measured with both a portable PAM instrument on site and a diving PAM under water in the habitat. In parallel, solar radiation was measured continuously above and under water by means of two three-channel dosimeters, ELDONET (Real Time Computer, Möhrendorf, Germany), in three wavelength ranges, UV-A, UV-B and PAR. The effective photosynthetic quantum yield decreased in all species in response to exposure to 15 min of solar radiation but recovered in the subsequent shade conditions within several hours. A 30-min exposure caused an even more profound photoinhibition from which the algae recovered only partially. Most of the effect was due to visible radiation, however, the UV wavelength range, and especially UV-B, considerably enhanced the decrease in photosynthetic quantum yield. In all species except Sargassum a significant photoinhibition was detected at their growth sites at high solar angles in the water column, measured with the diving PAM.

Monocyte chemoattractant protein-1 and macrophage infiltration in hypertensive kidney injury

BACKGROUND

We investigated whether monocyte chemoattractant protein-1 (MCP-1) is expressed in hypertensive nephrosclerosis, and tested the effect of angiotensin II type 1 receptor blockade on MCP-1 expression and macrophage (MPhi) infiltration.

METHODS

Rats with two-kidney, one-clip (2K1C) hypertension with and without treatment with the angiotensin II type 1 receptor antagonist valsartan (3 mg/kg/day) were studied. In these animals as well as in spontaneously hypertensive rats (SHR), stroke-prone SHR (SHR-SP), hypertensive mRen-2 transgenic rats (TGR), and respective control strains, MCP-1 expression in the kidney was investigated by Northern and Western blots and by immunohistochemistry. Glomerular and interstitial MPhis were counted.

RESULTS

In the nonclipped kidney of 2K1C rats, MCP-1 expression was elevated at 14 and 28 days when significant MPhi infiltration was present. MCP-1 was localized to glomerular endothelial and epithelial cells, interstitial and tubular cells, MPhis, and vascular smooth muscle cells. A similar pattern of MCP-1 staining was present in TGR kidneys, whereas MCP-1 expression was not increased in SHR and SHR-SP. Valsartan reduced but did not normalize blood pressure, blocked the induction of MCP-1 protein in 2K1C kidneys, and decreased interstitial MPhi infiltration significantly.

CONCLUSION

MCP-1 expression is increased in angiotensin II-dependent models of hypertensive nephrosclerosis and is temporally and spatially related to MPhi infiltration. The angiotensin II type 1 receptor mediates the induction of MCP-1.

On site photosynthetic performance of Atlantic green algae

Photosynthetic performance was measured on site in four common Atlantic green algae, Asparagopsis taxiforme, Valonia utricularia, Caulerpa racemosa and Codium taylori, in Gran Canaria, Canary Islands. The photosynthetic quantum yield was determined with a portable PAM instrument and with a diving PAM in the water column. Solar radiation was measured continuously above and in the water column by means of two three-channel dosimeters, ELDONET (Real Time Computer, Möhrendorf, Germany), in the UV-A, UV-B and PAR ranges. The effective photosynthetic quantum yield was found to be affected by exposure to solar radiation in as short as 15 min but recovered in the shade in most species within several hours. Only A. taxiforme failed to recover completely, and a 30-min exposure caused severe photoinhibition from which the algae recovered only partially. While most of the effect was due to the PAR wavelength range, the UV, and especially the UV-B, range considerably enhanced photoinhibition. In all four species, a significant inhibition was found even at their growth sites in the water column, measured with the diving PAM, at high solar angles.

Physical characterization of gravitaxis in Euglena gracilis

Gravitaxis in unicellular microorganisms like Euglena gracilis has been known for more than 100 years. The current model explains this phenomenon on the basis of a specific density difference between cell body and surrounding medium. In order to test the feasibility of the current model in terms of physical considerations the specific density of different Euglena gracilis cultures was determined. Depending on the culture conditions the specific density was in a range between 1.046 g mL-1 and 1.054 g mL-1. Size and gravitaxis measurements were performed in parallel, which allowed to relate the force applied to the lower membrane to the kinetic properties of gravitactic reorientation. A linear relationship between force and gravitaxis kinetics was found. A comparison between estimated activation energy of the proposed stretch-sensitive ion channels and energy supplied by the displacement of the lower membrane by the sedimentation of the cell body revealed that a focusing, an amplification and/or an integration period over time must be involved in the gravitactic signal transduction chain. Analysis of stimulus-response curves revealed an integration period of about 5 seconds before a gravitactic reorientation starts. The kinetics of gravitaxis at 1 x gn, and 0.12 x gn, was found to be similar. A hypothesis is presented that explains this finding on the basis of a combination of an integration period and an all-or-none reaction during gravitactic reorientation.

Circadian rhythm of gravitaxis in Euglena gracilis

Euglena gracilis, a unicellular, photosynthetic flagellate is a model system for environmentally controlled behavioral reactions. One pronounced reaction is the orientation with respect to gravity. In synchronized cultures with no cell growth a distinct circadian rhythm of negative gravitactic orientation could be observed. The main maximum of sensitivity was detected 5 h after the beginning of the subjective day, the main minimum 5 h before the beginning of the subjective day. Transferring synchronized cultures to continuous light resulted in an almost instantaneous loss of rhythmicity. In contrast, after transfer to permanent darkness cells exhibited a circadian rhythm with a progressive shortening of the period for more than 5 days. These findings are in contrast to the circadian rhythm of phototaxis in Euglena, where a free-running period of 24 h was observed. Parallel measurements of negative gravitactic orientation, velocity, cell shape as well as cAMP concentration in synchronized cultures revealed a circadian rhythm of all reactions. The results are discussed with regard to the possible role of cell shape and cAMP in gravitactic orientation.

Long-term cultivation of the flagellate Euglena gracilis

Euglena gracilis, a unicellular photosynthetic flagellate, serves as a model system in signal transduction research. To further study its complex gravitaxis, experiments under microgravity are desirable. In preparation for long-term experiments on a space station, an autonomous cultivation unit has been developed and the culture conditions and surveillance methods have been established. The running time of more than 600 d under closed conditions with light as the only source of energy confirmed the stability of the Euglena population and gave new insights into its behavior. Physicochemical parameters such as oxygen concentration, temperature and pH as well as physiological parameters including cell density, motility, gravitactic orientation and pigmentation were recorded on a frequent basis. The suitability of the botanical bioreaction to serve as an oxygen supplier for animals in a closed system was demonstrated.

A rapid, simple method for the isolation and characterization of the photoreceptor of Dictyostelium discoideum amoebae

A membrane-bound 45.5 kDa protein has been isolated from Dictyostelium discoideum amoebae. It shows an absorption spectrum, which closely resembles the action spectrum for amoebal phototaxis, leading to the conclusion that this protein might play an important role in the photoreception of Dictyostelium amoebae. For further characterization we employed phase partition in an aqueous polymer two-phase system, which was developed by Widell and Larsson for the separation of plasma membrane proteins of higher plants. This method clearly shows that the 45.5 kDa protein is a plasma membrane protein and not an intracellular protein. Furthermore, by using phase systems with increasing polymer concentrations, this simple and rapid purification of plasma membrane proteins allowed us to isolate the putative photoreceptor in one single step. Compared to standard biochemical methods phase partition provides an enormous facilitation of the isolation of D. discoideum membrane proteins.

Blue Light Induces Phosphorylation at Seryl Residues on a Pea (Pisum sativum L.) Plasma Membrane Protein

We have partially characterized the blue-light-stimulated in vitro phosphorylation of a membrane protein from etiolated Pisum sativum L. stems. Properties of the response have implicated its involvement in signal transduction of phototropic stimuli (T.W. Short, W.R. Briggs [1990] Plant Physiol 92: 179-185; P. Reymond, T.W. Short, W.R. Briggs [1992] Proc Natl Acad Sci USA 89: 4718- 4721). Analysis of proteolysis products and phosphoamino acidanalysis indicate that the substrate protein is phosphorylated on multiple seryl residues. Kinetics of the in vitro reaction show phosphorylation to be complete within 2 to 5 min at 30[deg]C in either light-exposed or dark-control plasma membrane preparations, regardless of whether the membranes were first solubilized in Triton X-100. Nucleotide competition assays show the kinase to be ATP specific. The pH optimum covers a broad range with a maximum near 7.5. A wide array of salts inhibits the phosphorylation at high concentrations, but millimolar concentrations of Mg2+ are required to form Mg.ATP complexes for maximal activity, whereas excess free Mg2+ or Ca2+ are not required for the reaction.