Macrophage SPAK deletion limits a low potassium-induced kidney inflammatory program.

Inadequate dietary potassium (K+) consumption is a significant contributor to poor cardiovascular outcomes. A diet with reduced K+ content has been shown to cause salt-sensitive increases in blood pressure. More recently we have also shown that reductions in blood K+ can cause direct kidney injury, independent of dietary sodium (Na+) content. Here we investigated the role of the kinase, SPAK, in this kidney injury response. We observed that global SPAK deletion protected the kidney from damaging effects of a diet high in Na+ and low in K+. We hypothesized kidney macrophages were contributing to the injury response and that macrophage-expressed SPAK is essential in this process. We observed SPAK protein expression in isolated macrophages in vitro. Culture in K+-deficient medium increased SPAK phosphorylation and caused SPAK to localize to cytosolic puncta, reminiscent of WNK bodies identified along the distal nephron epithelium. WNK1 also adopted a punctate staining pattern under low K+ conditions and SPAK phosphorylation was prevented by treatment with the WNK inhibitor, WNK463. Macrophage-specific SPAK deletion in vivo protected against the low K+-mediated renal inflammatory and fibrotic responses. Our results highlight an important role for macrophages, and macrophage-expressed SPAK, in the propagation of kidney damage that occurs in response to reduced dietary K+ consumption.

An analysis of the Chinese scheduled freighter network during the first year of the COVID-19 pandemic.

COVID-19 caused the vast majority of passenger flights to be grounded, but the crisis raised the importance of the network of dedicated cargo flights and, therefore, interest in its development. This paper aims to evaluate the Chinese scheduled freighter network (CSFN) via its topological properties and to explore its changes following the COVID-19 pandemic. Using spatial analysis with the complex network theory (CNT), the paper found that the CSFN displays small-world and scale-free network properties, similar to that of air passenger network. Hangzhou, Shenzhen and Nanjing are the dominant national hubs in the CSFN because they host the headquarters of many e-commerce giant enterprises and have relatively underutilized airport capacities. The CSFN has improved since the COVID-19 pandemic, with increased network average degree, clustering coefficient, and closeness, and reduced average path. These improvements were mainly driven by major hub cities whose centralities had been strengthened with more route connections. Since China's air passenger traffic had quickly restored in the second half of 2020, we argue that the changes in the CSFN during COVID-19 were unlikely to be a result of the substitution effect between freighter and passenger aircraft. It was more likely a result of the higher air cargo demand during the pandemic and airlines' realisation of the importance of freighter operations in China.

Activation of hypoxia-sensing pathways promotes renal ischemic preconditioning following myocardial infarction.

Ischemic heart disease is the leading cause of death worldwide and is frequently comorbid with chronic kidney disease. Physiological communication is known to occur between the heart and the kidney. Although primary dysfunction in either organ can induce dysfunction in the other, a clinical entity known as cardiorenal syndrome, mechanistic details are lacking. Here, we used a model of experimental myocardial infarction (MI) to test effects of chronic cardiac ischemia on acute and chronic kidney injury. Surprisingly, chronic cardiac damage protected animals from subsequent acute ischemic renal injury, an effect that was accompanied by evidence of chronic kidney hypoxia. The protection observed post-MI was similar to protection observed in a separate group of healthy animals housed in ambient hypoxic conditions prior to kidney injury, suggesting a common mechanism. There was evidence that chronic cardiac injury activates renal hypoxia-sensing pathways. Increased renal abundance of several glycolytic enzymes following MI suggested that a shift toward glycolysis may confer renal ischemic preconditioning. In contrast, effects on chronic renal injury followed a different pattern, with post-MI animals displaying worsened chronic renal injury and fibrosis. These data show that although chronic cardiac injury following MI protected against acute kidney injury via activation of hypoxia-sensing pathways, it worsened chronic kidney injury. The results further our understanding of cardiorenal signaling mechanisms and have implications for the treatment of heart failure patients with associated renal disease.NEW & NOTEWORTHY Experimental myocardial infarction (MI) protects from subsequent ischemic acute kidney injury but worsens chronic kidney injury. Observed protection from ischemic acute kidney injury after MI was accompanied by chronic kidney hypoxia and increased renal abundance of hypoxia-inducible transcripts. These data support the idea that MI confers protection from renal ischemic injury via chronic renal hypoxia and activation of downstream hypoxia-inducible signaling pathways.

COVID-19 and bailout policy: The case of Virgin Australia.

The impact of COVID-19 on air transport is unprecedented and some well-known airline brands may disappear as a result. Governments around the world have responded swiftly to cushion the financial impact by offering direct wage subsidies, tax relief, loans, etc. This paper explores the government's appropriate responses to failing airlines' bailout request by examining the case of Virgin Australia. Following the bailout policy principles established in the literature, we suggest that bankruptcy protection should be considered as the first solution to a failing carrier. A bailout decision should be guided by a set of principles and procedures, which should not be taken lightly. Our analysis also shows that the government cannot take a hands-off approach in the absence of private lenders and investors, as the costs to consumers and regional residents would be huge if the carrier could not get through the COVID-19 pandemic. A minimum level of assistance with conditions might be needed to maintain market competition.

COVID-19 impacts on general aviation - Comparative experiences, governmental responses and policy imperatives.

This article catalogues experiences of the general aviation sector as it progressively encountered the challenges of COVID-19 in the early part of 2020. The article focuses primarily on the Australian marketplace as a contribution to the body of knowledge in an under-researched industry sector. The article draws on literature pertaining to prior pandemic experience to enquire about the level of precursory preparedness in the sector, and then utilises data from 12 semi-structured interviews with experienced industry participants locally and internationally. The key findings suggest that there has been a lack of applied learning by policy makers in the past, and that generic support on offer now does not address the long term resilience of the sector nor does it address a pathway for future sudden moments of dislocation. Policies which purport to support aviation should be crafted in a way that engages all levels of industry rather than be airline centric.

Lipopolysaccharide induces filtrate leakage from renal tubular lumina into the interstitial space via a proximal tubular Toll-like receptor 4-dependent pathway and limits sensitivity to fluid therapy in mice.

Sustained oliguria during fluid resuscitation represents a perplexing problem in patients undergoing therapy for septic acute kidney injury. Here, we tested whether lipopolysaccharide induces filtrate leakage from the proximal tubular lumen into the interstitium, thus disturbing the recovery of urine output during therapy, such as fluid resuscitation, aiming to restore the glomerular filtration rate. Intravital imaging of the tubular flow rate in the proximal tubules in mice showed that lipopolysaccharide did not change the inflow rate of proximal tubule filtrate, reflecting an unchanged glomerular filtration rate, but significantly reduced the outflow rate, resulting in oliguria. Lipopolysaccharide disrupted tight junctions in proximal tubules and induced both paracellular leakage of filtered molecules and interstitial accumulation of extracellular fluid. These changes were diminished by conditional knockout of Toll-like receptor 4 in the proximal tubules. Importantly, these conditional knockout mice showed increased sensitivity to fluid resuscitation and attenuated acute kidney injury. Thus, lipopolysaccharide induced paracellular leakage of filtrate into the interstitium via a Toll-like receptor 4-dependent mechanism in the proximal tubules of endotoxemic mice. Hence, this leakage might diminish the efficacy of fluid resuscitation aiming to maintain renal hemodynamics and glomerular filtration rate.

Exploring the roles of high-speed train, air and coach services in the spread of COVID-19 in China.

To understand the roles of different transport modes in the spread of COVID-19 pandemic across Chinese cities, this paper looks at the factors influencing the number of imported cases from Wuhan and the spread speed and pattern of the pandemic. We find that frequencies of air flights and high-speed train (HST) services out of Wuhan are significantly associated with the number of COVID-19 cases in the destination cities. The presence of an airport or HST station at a city is significantly related to the speed of the pandemic spread, but its link with the total number of confirmed cases is weak. The farther the distance from Wuhan, the lower number of cases in a city and the slower the dissemination of the pandemic. The longitude and latitude coordinates do not have a significant relationship with the number of total cases but can increase the speed of the COVID-19 spread. Specifically, cities in the higher longitudinal region tended to record a COVID-19 case earlier than their counterparties in the west. Cities in the north were more likely to report the first case later than those in the south. The pandemic may emerge in large cities earlier than in small cities as GDP is a factor positively associated with the spread speed.

Noninvasive quantitative magnetization transfer MRI reveals tubulointerstitial fibrosis in murine kidney.

Excessive tissue scarring, or fibrosis, is a critical contributor to end stage renal disease, but current clinical tests are not sufficient for assessing renal fibrosis. Quantitative magnetization transfer (qMT) MRI provides indirect information about the macromolecular composition of tissues. We evaluated measurements of the pool size ratio (PSR, the ratio of immobilized macromolecular to free water protons) obtained by qMT as a biomarker of tubulointerstitial fibrosis in a well-established murine model with progressive renal disease. MR images were acquired from 16-week-old fibrotic hHB-EGFTg/Tg mice and normal wild-type (WT) mice (N = 12) at 7 T. QMT parameters were derived using a two-pool five-parameter fitting model. A normal range of PSR values in the cortex and outer stripe of outer medulla (CR + OSOM) was determined by averaging across voxels within WT kidneys (mean ± 2SD). Regions in diseased mice whose PSR values exceeded the normal range above a threshold value (tPSR) were identified and measured. The spatial distribution of fibrosis was confirmed using picrosirius red stains. Compared with normal WT mice, scattered clusters of high PSR regions were observed in the OSOM of hHB-EGFTg/Tg mouse kidneys. Moderate increases in mean PSR (mPSR) of CR + OSOM regions were observed across fibrotic kidneys. The abnormally high PSR regions (% area) detected by the tPSR were significantly increased in hHB-EGFTg/Tg mice, and were highly correlated with regions of fibrosis detected by histological fibrosis indices measured from picrosirius red staining. Renal tubulointerstitial fibrosis in OSOM can thus be assessed by qMT MRI using an appropriate analysis of PSR. This technique may be used as an imaging biomarker for chronic kidney diseases.

Low potassium activation of proximal mTOR/AKT signaling is mediated by Kir4.2.

The renal epithelium is sensitive to changes in blood potassium (K+). We identify the basolateral K+ channel, Kir4.2, as a mediator of the proximal tubule response to K+ deficiency. Mice lacking Kir4.2 have a compensated baseline phenotype whereby they increase their distal transport burden to maintain homeostasis. Upon dietary K+ depletion, knockout animals decompensate as evidenced by increased urinary K+ excretion and development of a proximal renal tubular acidosis. Potassium wasting is not proximal in origin but is caused by higher ENaC activity and depends upon increased distal sodium delivery. Three-dimensional imaging reveals Kir4.2 knockouts fail to undergo proximal tubule expansion, while the distal convoluted tubule response is exaggerated. AKT signaling mediates the dietary K+ response, which is blunted in Kir4.2 knockouts. Lastly, we demonstrate in isolated tubules that AKT phosphorylation in response to low K+ depends upon mTORC2 activation by secondary changes in Cl- transport. Data support a proximal role for cell Cl- which, as it does along the distal nephron, responds to K+ changes to activate kinase signaling.

Inactivation of the E-prostanoid 3 receptor attenuates the angiotensin II pressor response via decreasing arterial contractility.

OBJECTIVE: The present studies aimed at elucidating the role of prostaglandin E(2) receptor subtype 3 (E-prostanoid [EP] 3) in regulating blood pressure. METHODS AND RESULTS: Mice bearing a genetic disruption of the EP3 gene (EP(3)(-/-)) exhibited reduced baseline mean arterial pressure monitored by both tail-cuff and carotid arterial catheterization. The pressor responses induced by EP3 agonists M&B28767 and sulprostone were markedly attenuated in EP3(-/-) mice, whereas the reduction of blood pressure induced by prostaglandin E(2) was comparable in both genotypes. Vasopressor effect of acute or chronic infusion of angiotensin II (Ang II) was attenuated in EP3(-/-) mice. Ang II-induced vasoconstriction in mesenteric arteries decreased in EP3(-/-) group. In mesenteric arteries from wild-type mice, Ang II-induced vasoconstriction was inhibited by EP3 selective antagonist DG-041 or L798106. The expression of Arhgef-1 is attenuated in EP3 deficient mesenteric arteries. EP3 antagonist DG-041 diminished Ang II-induced phosphorylation of myosin light chain 20 and myosin phosphatase target subunit 1 in isolated mesenteric arteries. Furthermore, in vascular smooth muscle cells, Ang II-induced intracellular Ca(2+) increase was potentiated by EP3 agonist sulprostone but inhibited by DG-041. CONCLUSIONS: Activation of the EP3 receptor raises baseline blood pressure and contributes to Ang II-dependent hypertension at least partially via enhancing Ca(2+) sensitivity and intracellular calcium concentration in vascular smooth muscle cells. Selective targeting of the EP3 receptor may represent a potential therapeutic target for the treatment of hypertension.

The comparisons of procalcitonin and age between mild and severe Hand, foot, and mouth disease.

Background: Hand, foot, and mouth disease (HFMD) is an epidemic infectious disease in children, usually associated with fever, mouth lesions, and limb rashes. Although benign and self-limiting, it can be dangerous or even fatal in rare cases. Early identification of severe cases is crucial to ensure optimal care. Procalcitonin (PCT) is an early marker for predicting sepsis. Therefore, in this study, we aimed to investigate the significance of PCT levels, age, lymphocyte subsets, N-terminal pro-brain natriuretic peptide (BNP) in the early diagnosis of severe HFMD. Methods: Using strict inclusion and exclusion criteria, we retrospectively enrolled 183 children with HFMD between January 2020 and August 2021 and divided them into mild (76 cases) and severe (107 cases) groups according to their condition. Data on the patients' PCT levels, lymphocyte subsets, and clinical characteristics at admission were evaluated and compared using the Student's t-test and χ2 test. Results: We found that compared with mild disease forms, the severe disease forms were associated with higher blood PCT levels (P=0.001) and lower ages of onset (P<0.001). The percentages of lymphocyte subsets, including suppressor T cells (CD3+CD8+), T lymphocytes (CD3+), T helper cells (CD3+CD4+), natural killer cells (CD16+56+), and B lymphocytes (CD19+), were identical between the two disease forms in patients under 3 years of age. Conclusions: Age and blood PCT levels play a vital role in the early identification of severe HFMD.

High sodium intake does not worsen low potassium-induced kidney damage.

High sodium and low potassium intake have both been linked to poor cardiovascular health outcomes and increased mortality rates. A combination of the two is thought to be particularly detrimental. While mechanisms are multiple, the kidney is an important target of harmful effects and low potassium influences on both proximal and distal nephron segments are especially potent. We recently reported that a combined high sodium/low potassium diet causes kidney injury and that low potassium in isolation can have similar effects. However, how sodium intake alters this process is not well-understood. Here we tested the hypothesis that a high sodium intake amplifies effects of low dietary potassium on kidney injury. We observed adding high sodium to low potassium caused an expected increase in blood pressure, but did not worsen markers of kidney injury, inflammation, and fibrosis. It also did not increase abundance or phosphorylation of the sodium chloride cotransporter or its regulatory kinases, SPAK and OxSR1, known renal targets of low potassium. Findings support the claim that dietary potassium deficiency, and not high sodium, is a dominant factor affecting kidney injury in animal models of high sodium/low potassium intake. This suggests further investigation is required to identify optimal ranges of sodium and potassium intake in both healthy populations and in those with kidney disease.

Thiazolidinediones expand body fluid volume through PPARgamma stimulation of ENaC-mediated renal salt absorption.

Thiazolidinediones (TZDs) are widely used to treat type 2 diabetes mellitus; however, their use is complicated by systemic fluid retention. Along the nephron, the pharmacological target of TZDs, peroxisome proliferator-activated receptor-gamma (PPARgamma, encoded by Pparg), is most abundant in the collecting duct. Here we show that mice treated with TZDs experience early weight gain from increased total body water. Weight gain was blocked by the collecting duct-specific diuretic amiloride and was also prevented by deletion of Pparg from the collecting duct, using Pparg (flox/flox) mice. Deletion of collecting duct Pparg decreased renal Na(+) avidity and increased plasma aldosterone. Treating cultured collecting ducts with TZDs increased amiloride-sensitive Na(+) absorption and Scnn1g mRNA (encoding the epithelial Na(+) channel ENaCgamma) expression through a PPARgamma-dependent pathway. These studies identify Scnn1g as a PPARgamma target gene in the collecting duct. Activation of this pathway mediates fluid retention associated with TZDs, and suggests amiloride might provide a specific therapy.

[Authentication of Lonicera japonica using bidirectional PCR amplification of specific alleles].

OBJECTIVE: To identify SNP in flos Lonicerae, and authenticate Lonicera japonica from its adulterants and the mixture by using bidirectional PCR amplification of specific alleles (Bi-PASA). METHOD: SNP of L. japonica and its adulterants was identified by using ClustulW to align trnL-trnF sequences of the Lonicera genus from GenBank database. Bi-PASA primer was designed and the PCR reaction systems including annealing temperature optimized. Optimized result was performed in 84 samples to authenticate L. japonica, its adulterants and the mixture. RESULT: When the annealing temperature was 61 degrees C, DNA from L. japonica would be amplified 468 bp whereas PCR products from all of the 9 adulterants were 324 bp. The established method also can detect 5% of intentional adulteration DNA into L. japonica. CONCLUSION: The Bi-SPASA could authenticate L. japonica from its adulterants and the mixture.

Kir4.2 mediates proximal potassium effects on glutaminase activity and kidney injury.

Inadequate potassium (K+) consumption correlates with increased mortality and poor cardiovascular outcomes. Potassium effects on blood pressure have been described previously; however, whether or not low K+ independently affects kidney disease progression remains unclear. Here, we demonstrate that dietary K+ deficiency causes direct kidney injury. Effects depend on reduced blood K+ and are kidney specific. In response to reduced K+, the channel Kir4.2 mediates altered proximal tubule (PT) basolateral K+ flux, causing intracellular acidosis and activation of the enzyme glutaminase and the ammoniagenesis pathway. Deletion of either Kir4.2 or glutaminase protects from low-K+ injury. Reduced K+ also mediates injury and fibrosis in a model of aldosteronism. These results demonstrate that the PT epithelium, like the distal nephron, is K+ sensitive, with reduced blood K+ causing direct PT injury. Kir4.2 and glutaminase are essential mediators of this injury process, and we identify their potential for future targeting in the treatment of chronic kidney disease.

Cyclooxygenase-2 in adipose tissue macrophages limits adipose tissue dysfunction in obese mice.

Obesity-associated complications are causing increasing morbidity and mortality worldwide. Expansion of adipose tissue in obesity leads to a state of low-grade chronic inflammation and dysregulated metabolism, resulting in insulin resistance and metabolic syndrome. Adipose tissue macrophages (ATMs) accumulate in obesity and are a source of proinflammatory cytokines that further aggravate adipocyte dysfunction. Macrophages are rich sources of cyclooxygenase (COX), the rate limiting enzyme for prostaglandin E2 (PGE2) production. When mice were fed a high-fat diet (HFD), ATMs increased expression of COX-2. Selective myeloid cell COX-2 deletion resulted in increased monocyte recruitment and proliferation of ATMs, leading to increased proinflammatory ATMs with decreased phagocytic ability. There were increased weight gain and adiposity, decreased peripheral insulin sensitivity and glucose utilization, increased adipose tissue inflammation and fibrosis, and abnormal adipose tissue angiogenesis. HFD pair-feeding led to similar increases in body weight, but mice with selective myeloid cell COX-2 still exhibited decreased peripheral insulin sensitivity and glucose utilization. Selective myeloid deletion of the macrophage PGE2 receptor subtype, EP4, produced a similar phenotype, and a selective EP4 agonist ameliorated the metabolic abnormalities seen with ATM COX-2 deletion. Therefore, these studies demonstrated that an ATM COX-2/PGE2/EP4 axis plays an important role in inhibiting adipose tissue dysfunction.

Macrophage interferon regulatory factor 4 deletion ameliorates aristolochic acid nephropathy via reduced migration and increased apoptosis.

Aristolochic acid (AA) is the causative nephrotoxic alkaloid in AA nephropathy, which results in a tubulointerstitial fibrosis. AA causes direct proximal tubule damage as well as an influx of macrophages, although the role of macrophages in pathogenesis is poorly understood. Here, we demonstrate that AA directly stimulates migration, inflammation, and ROS production in macrophages ex vivo. Cells lacking interferon regulatory factor 4 (IRF4), a known regulator of macrophage migration and phenotype, had a reduced migratory response, though effects on ROS production and inflammation were preserved or increased relative to WT cells. Macrophage-specific IRF4-knockout mice were protected from both acute and chronic kidney effects of AA administration based on functional and histological analysis. Renal macrophages from kidneys of AA-treated macrophage-specific IRF4-knockout mice demonstrated increased apoptosis and ROS production compared with WT controls, indicating that AA directly polarizes macrophages to a promigratory and proinflammatory phenotype. However, knockout mice had reduced renal macrophage abundance following AA administration. While macrophages lacking IRF4 can adopt a proinflammatory phenotype upon AA exposure, their inability to migrate to the kidney and increased rates of apoptosis upon infiltration provide protection from AA in vivo. These results provide evidence of direct AA effects on macrophages in AA nephropathy and add to the growing body of evidence that supports a key role of IRF4 in modulating macrophage function in kidney injury.

Price wars and price collusion in China's airline markets.

In the absence of an effective antitrust law, both fare wars and price collusion have been pervasive in China's airline markets, causing concern for both airlines and consumers. A study of monthly airfare data from 2002 to 2004 confirms that fare wars occur periodically, as well as price collusion. Both tend to be short-lived. The fact that collusion is more likely to occur in January and April when demand is high, as revealed by China Eastern's and China Southern's price-war and collusion models, has been confirmed by interview information obtained from the airlines' sales managers. However, there is also evidence in these models suggesting that collusion can be more easily formed when demand is low. High airport concentration measured by the HHI may facilitate collusion in certain circumstances, but it may also lead to more price wars under other conditions. Concentration in both airports and routes does not appear to systematically affect the occurrence of fare wars and collusion in all the models estimated. We also reject the possibility that mutual forbearance due to multimarket contact plays any important anti-competitive role in China's airline markets.

The impact of the COVID-19 pandemic on current tertiary aviation education and future careers: Students' perspective.

This study investigates Australian undergraduate tertiary aviation students' perceptions of the aviation industry and skills required to succeed following the COVID-19 pandemic. By developing an understanding of the skills students perceive to be necessary for their careers following the COVID-19 pandemic, comparisons can be drawn with industry perspectives to determine whether these perspectives align and, more importantly, support students' successful development of skills as sought by the industry. An online survey of current undergraduate tertiary aviation students at Australian universities was conducted to determine the perceived impediments, additional skills required, post-graduation plans and how university courses should evolve post-COVID-19. The results show that students are cognisant of the current oversupply of aviation professionals due to the downturn in the industry and are seeking further support with the development of non-technical skills to better prepare themselves to be competitive following graduation. These findings have implications for both undergraduate aviation students and universities offering an undergraduate aviation program. By considering these findings universities can adapt their programs to better prepare students and support the development of skilled aviation professionals, equipped to deal with challenges of the post-COVID-19 aviation industry.

Antihypertensive effects of selective prostaglandin E2 receptor subtype 1 targeting.

Clinical use of prostaglandin synthase-inhibiting NSAIDs is associated with the development of hypertension; however, the cardiovascular effects of antagonists for individual prostaglandin receptors remain uncharacterized. The present studies were aimed at elucidating the role of prostaglandin E2 (PGE2) E-prostanoid receptor subtype 1 (EP1) in regulating blood pressure. Oral administration of the EP1 receptor antagonist SC51322 reduced blood pressure in spontaneously hypertensive rats. To define whether this antihypertensive effect was caused by EP1 receptor inhibition, an EP1-null mouse was generated using a "hit-and-run" strategy that disrupted the gene encoding EP1 but spared expression of protein kinase N (PKN) encoded at the EP1 locus on the antiparallel DNA strand. Selective genetic disruption of the EP1 receptor blunted the acute pressor response to Ang II and reduced chronic Ang II-driven hypertension. SC51322 blunted the constricting effect of Ang II on in vitro-perfused preglomerular renal arterioles and mesenteric arteriolar rings. Similarly, the pressor response to EP1-selective agonists sulprostone and 17-phenyltrinor PGE2 were blunted by SC51322 and in EP1-null mice. These data support the possibility of targeting the EP1 receptor for antihypertensive therapy.