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Background Acute kidney injury (AKI) in deceased donors is not associated with graft failure (GF). We hypothesize that hemodynamic AKI (hAKI) comprises the majority of donor AKI and may explain this lack of association. Methods In this ancillary analysis of the Deceased Donor Study, 428 donors with available charts were selected to identify those with and without AKI. AKI cases were classified as hAKI, intrinsic (iAKI), or mixed (mAKI) based on majority adjudication by three nephrologists. We evaluated the associations between AKI phenotypes and delayed graft function (DGF), 1-year eGFR and GF. We also evaluated differences in urine biomarkers among AKI phenotypes. Results Of the 291 (68%) donors with AKI, 106 (36%) were adjudicated as hAKI, 84 (29%) as iAKI and 101 (35%) as mAKI. Of the 856 potential kidneys, 669 were transplanted with 32% developing DGF and 5% experiencing GF. Median 1-year eGFR was 53 (IQR: 41–70) ml/min/1.73m2. Compared to non-AKI, donors with iAKI had higher odds DGF [aOR (95%CI); 4.83 (2.29, 10.22)] and had lower 1-year eGFR [adjusted B coefficient (95% CI): -11 (-19, -3) mL/min/1.73 m2]. hAKI and mAKI were not associated with DGF or 1-year eGFR. Rates of GF were not different among AKI phenotypes and non-AKI. Urine biomarkers such as NGAL, LFABP, MCP-1, YKL-40, cystatin-C and albumin were higher in iAKI. Conclusion iAKI was associated with higher DGF and lower 1-year eGFR but not with GF. Clinically phenotyped donor AKI is biologically different based on biomarkers and may help inform decisions regarding organ utilization.

In Huntington disease (HD), an expanded polyglutamine (polyQ > 37) sequence within huntingtin (htt) exon1 leads to enhanced disease risk. It has proved difficult, however, to determine whether the toxic form generated by polyQ expansion is a misfolded or avid-binding monomer, an α-helix-rich oligomer, or a β-sheet-rich amyloid fibril. Here we describe an engineered htt exon1 analog featuring a short polyQ sequence that nonetheless quickly forms amyloid fibrils and causes HD-like toxicity in rat neurons and Drosophila. Additional modifications within the polyQ segment produce htt exon1 analogs that populate only spherical oligomers and are non-toxic in cells and flies. Furthermore, in mixture with expanded-polyQ htt exon1, the latter analogs in vitro suppress amyloid formation and promote oligomer formation, and in vivo rescue neurons and flies expressing mhtt exon1 from dysfunction and death. Thus, in our experiments, while htt exon1 toxicity tracks with aggregation propensity, it does so in spite of the toxic construct's possessing polyQ tracts well below those normally considered to be disease-associated. That is, aggregation propensity proves to be a more accurate surrogate for toxicity than is polyQ repeat length itself, strongly supporting a major toxic role for htt exon1 aggregation in HD. In addition, the results suggest that the aggregates that are most toxic in these model systems are amyloid-related. These engineered analogs are novel tools for mapping properties of polyQ self-assembly intermediates and products that should similarly be useful in the analysis of other expanded polyQ diseases. Small molecules with similar amyloid inhibitory properties might be developed into effective therapeutic agents.

Background AKI is common in patients hospitalized with coronavirus disease 2019 (COVID-19). Risk factors for AKI requiring dialysis (AKI-D) are not fully understood. We aimed to identify risk factors associated with AKI-D and AKI not requiring dialysis (AKI-ND). Methods We reviewed electronic health records of 3186 patients aged ≥18 years old who were hospitalized with COVID-19 across six hospitals. Patient characteristics, urinalysis findings, and inflammatory markers were analyzed for association with in-hospital AKI status (AKI-D, AKI-ND, or no AKI), and we subsequently evaluated mortality. Results After adjustment for multiple covariates, higher baseline eGFR was associated with 30% lower odds of AKI-D and 11% lower odds of AKI-ND (for AKI-D, OR, 0.70; 95% CI, 0.64 to 0.77; for AKI-ND, OR, 0.89; 95% CI, 0.85 to 0.92). Patients with obesity and those who were Latino had increased odds of AKI-D, whereas patients with congestive heart failure or diabetes with complications had increased odds of AKI-ND. Females had lower odds of in-hospital AKI (for AKI-D, OR, 0.28; 95% CI, 0.17 to 0.46; for AKI-ND, OR, 0.83; 95% CI, 0.70 to 0.99). After adjustment for covariates and baseline eGFR, 1–4+ protein on initial urinalysis was associated with a nine-fold increase in odds of AKI-D (OR, 9.00; 95% CI, 2.16 to 37.38) and more than two-fold higher odds of AKI-ND (OR, 2.28; 95% CI, 1.66 to 3.13). Findings of 1–3+ blood and trace glucose on initial urinalysis were also associated with increased odds of both AKI-D and AKI-ND. AKI-D and AKI-ND were associated with in-hospital death (for AKI-D, OR, 2.64; 95% CI, 1.13 to 6.17; for AKI-ND, OR, 2.44; 95% CI, 1.77 to 3.35). Conclusions Active urine sediments, even after adjustment for baseline kidney function, and reduced baseline eGFR are significantly associated with increased odds of AKI-D and AKI-ND. In-hospital AKI was associated with in-hospital death. These findings may help prognosticate patients hospitalized with COVID-19.

In March 2020, the COVID-19 pandemic became an increasingly urgent issue of public health concern in the United States. Patients on dialysis are considered to be at increased risk for infection due to their medical comorbidities and need for continued face-to-face encounters in dialysis units. In our outpatient dialysis practice, 42 out of 269 patients (15.6%) were infected with COVID-19 during the first wave of the pandemic. In this retrospective report, we review issues of infection control, access to interventional procedures, and communication encountered in our practice. We discuss lessons learned in patient outcomes and the importance of transitioning patients to home modalities. Further planning for a potential second wave of COVID-19 may help ensure improved quality of care for patients in the dialysis program.

Purpose of Review Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are commonly used anti-hypertensive medications in a number of clinical settings. They are often used interchangeably, but we pose the provocative question as to whether they should be. We review the literature to evaluate for any differences in efficacy between the two classes in order to determine if the greater side effects associated with angiotensin-converting enzyme inhibitors are offset by any advantageous effects on outcomes to warrant their use over angiotensin receptor blockers. Recent Findings In many clinical scenarios, the data supports similar efficacy between ACE inhibitors and ARBs, while in a minority of others, there are murky signals from previous trials that suggest ACE inhibitors may be better. However, when reviewing the literature in its entirety, and taking into account recently published pooled analysis and head to head trials, it is reasonable to conclude that ACE inhibitors and ARBs have similar efficacy. This is in contrast to data on adverse effects, which consistently favors the use of ARBs. Summary From the available data, it is reasonable to conclude that ACE inhibitors and ARBs have equal efficacy yet unequal adverse effects. It is in this context that we take the provocative stance that ACE inhibitors should not be used to treat hypertension.

Transforming growth factor (TGF) β1, β2, and β3 (TGF-β1–TGF-β3, respectively) are small secreted signaling proteins that each signal through the TGF-β type I and type II receptors (TβRI and TβRII, respectively). However, TGF-β2, which is well-known to bind TβRII several hundred-fold more weakly than TGF-β1 and TGF-β3, has an additional requirement for betaglycan, a membrane-anchored nonsignaling receptor. Betaglycan has two domains that bind TGF-β2 at independent sites, but how it binds TGF-β2 to potentiate TβRII binding and how the complex with TGF-β, TβRII, and betaglycan undergoes the transition to the signaling complex with TGF-β, TβRII, and TβRI are not understood. To investigate the mechanism, the binding of the TGF-βs to the betaglycan extracellular domain, as well as its two independent binding domains, either directly or in combination with the TβRI and TβRII ectodomains, was studied using surface plasmon resonance, isothermal titration calorimetry, and size-exclusion chromatography. These studies show that betaglycan binds TGF-β homodimers with a 1:1 stoichiometry in a manner that allows one molecule of TβRII to bind. These studies further show that betaglycan modestly potentiates the binding of TβRII and must be displaced to allow TβRI to bind. These findings suggest that betaglycan functions to bind and concentrate TGF-β2 on the cell surface and thus promote the binding of TβRII by both membrane-localization effects and allostery. These studies further suggest that the transition to the signaling complex is mediated by the recruitment of TβRI, which simultaneously displaces betaglycan and stabilizes the bound TβRII by direct receptor–receptor contact.

The red shift in the fluorescence excitation spectra of thioflavin dyes upon binding to fibrils has been a boon to the amyloid field, offering simple and effective methods for the qualitative detection of amyloid in tissue samples and for quantitation of particular fibril preparations with gravimetric linearity. The quantitative aspect of the thioflavin T (ThT) response, however, comes with an important caveat that bestows both significant limitations and great untapped power. It is now well established that amyloid fibrils of different proteins, as well as polymorphic fibrils of the same protein, can exhibit vastly different ThT fluorescence intensities for the same weight concentration of aggregates. Furthermore, the aggregated intermediates commonly observed in amyloid assembly reactions can exhibit aggregate weight-normalized (AWN) ThT fluorescence intensities that vary from essentially zero through a wide range of intermediate values before reaching the intensity of homogeneous, mature amyloid. These features make it very difficult to quantitatively interpret, without additional data, the time-dependent development of ThT fluorescence intensity in an assembly reaction. In this chapter, we describe a method for coupling ex situ ThT fluorescence determinations with an analytical HPLC supported sedimentation assay (also described in detail) that can provide significant new insights into amyloid assembly reactions. The time dependent aggregation data provided by the sedimentation assay reveals a time course of aggregation that is largely independent of aggregate properties. In addition, the combination of these data with ThT measurements of the same reaction time points reveals important aspects of average aggregate structure at each time point. Examples of the use and potential value of AWN-ThT measurements during amyloid assembly Aβ and polyglutamine peptides are provided.

The red shift in the fluorescence excitation spectra of thioflavin dyes upon binding to fibrils has been a boon to the amyloid field, offering simple and effective methods for the qualitative detection of amyloid in tissue samples and for quantitation of particular fibril preparations with gravimetric linearity. The quantitative aspect of the thioflavin T (ThT) response, however, comes with an important caveat that bestows both significant limitations and great untapped power. It is now well established that amyloid fibrils of different proteins, as well as polymorphic fibrils of the same protein, can exhibit vastly different ThT fluorescence intensities for the same weight concentration of aggregates. Furthermore, the aggregated intermediates commonly observed in amyloid assembly reactions can exhibit aggregate weight-normalized (AWN) ThT fluorescence intensities that vary from essentially zero through a wide range of intermediate values before reaching the intensity of homogeneous, mature amyloid. These features make it very difficult to quantitatively interpret, without additional data, the time-dependent development of ThT fluorescence intensity in an assembly reaction. In this chapter, we describe a method for coupling ex situ ThT fluorescence determinations with an analytical HPLC supported sedimentation assay (also described in detail) that can provide significant new insights into amyloid assembly reactions. The time dependent aggregation data provided by the sedimentation assay reveals a time course of aggregation that is largely independent of aggregate properties. In addition, the combination of these data with ThT measurements of the same reaction time points reveals important aspects of average aggregate structure at each time point. Examples of the use and potential value of AWN-ThT measurements during amyloid assembly Aβ and polyglutamine peptides are provided.

Transforming growth factor (TGF) β1, β2, and β3 (TGF-β1-TGF-β3, respectively) are small secreted signaling proteins that each signal through the TGF-β type I and type II receptors (TβRI and TβRII, respectively). However, TGF-β2, which is well-known to bind TβRII several hundred-fold more weakly than TGF-β1 and TGF-β3, has an additional requirement for betaglycan, a membrane-anchored nonsignaling receptor. Betaglycan has two domains that bind TGF-β2 at independent sites, but how it binds TGF-β2 to potentiate TβRII binding and how the complex with TGF-β, TβRII, and betaglycan undergoes the transition to the signaling complex with TGF-β, TβRII, and TβRI are not understood. To investigate the mechanism, the binding of the TGF-βs to the betaglycan extracellular domain, as well as its two independent binding domains, either directly or in combination with the TβRI and TβRII ectodomains, was studied using surface plasmon resonance, isothermal titration calorimetry, and size-exclusion chromatography. These studies show that betaglycan binds TGF-β homodimers with a 1:1 stoichiometry in a manner that allows one molecule of TβRII to bind. These studies further show that betaglycan modestly potentiates the binding of TβRII and must be displaced to allow TβRI to bind. These findings suggest that betaglycan functions to bind and concentrate TGF-β2 on the cell surface and thus promote the binding of TβRII by both membrane-localization effects and allostery. These studies further suggest that the transition to the signaling complex is mediated by the recruitment of TβRI, which simultaneously displaces betaglycan and stabilizes the bound TβRII by direct receptor-receptor contact.

Lamin proteins contribute to nuclear structure and function, primarily at the inner nuclear membrane. The post- translational processing pathway of lamin A includes farnesylation of the C-terminus, likely to increase membrane association, and subsequent proteolytic cleavage of the C-terminus. Hutchinson Gilford progeria syndrome is a premature aging disorder wherein a mutant version of lamin A, D50 lamin A, retains its farnesylation. We report here that membrane association of far- nesylated D50 lamin A tail domains requires calcium. Experimental evidence and molecular dynamics simulations collectively suggest that the farnesyl group is sequestered within a hydrophobic region in the tail domain in the absence of calcium. Calcium binds to the tail domain with an affinity KD z 250 mM where it alters the structure of the Ig-fold and increases the solvent acces- sibility of the C-terminus. In 2 mM CaCl2, the affinity of the farnesylated protein to a synthetic membrane is KD z 2 mM, as measured with surface plasmon resonance, but showed a combination of aggregation and binding. Membrane binding in the absence of calcium could not be detected. We suggest that a conformational change induced in D50 lamin A with divalent cat- ions plays a regulatory role in the posttranslational processing of lamin A, which may be important in disease pathogenesis.