Both endothelium and afferent nerve endings play a role in acetylcholine-induced renal vasodilation

Association between cholinesterase inhibitors and kidney function decline in patients with Alzheimer's dementia

Preclinical evidence shows that activation of the cholinergic anti-inflammatory pathway (CAP) may have direct and indirect beneficial effects on the kidney. Cholinesterase inhibitors (ChEIs) are specific Alzheimer's dementia (AD) therapies that block the action of cholinesterases and activate CAP. Here, we explored a plausible effect of ChEIs on slowing kidney function decline by comparing the risk of CKD progression among patients with newly diagnosed AD that initiated ChEI or not within 90 days. Using complete information of routine serum creatinine tests, we evaluated changes in estimated glomerular filtration rate (eGFR) and defined the outcome of chronic kidney disease (CKD) progression as the composite of an eGFR decline of over 30%, initiation of dialysis/transplant or death attributed to CKD. A secondary outcome was death. Inverse probability of treatment-weighted Cox regression was used to estimate hazard ratios. Among 11, 898 patients, 6,803 started on ChEIs and 5,095 did not. Mean age was 80 years (64% women) and the mean eGFR was 68 ml/min/1.73m². During a median 3.0 years of follow-up, and compared to non-use, ChEI use was associated with 18% lower risk of CKD progression (1,231 events, adjusted hazard ratio 0.82; 95% confidence interval 0.71-0.96) and a 21% lower risk of death (0.79; 0.72-0.86). Results were consistent across subgroups, ChEI subclasses and after accounting for competing risks. Thus, in patients with AD undergoing routine care, use of ChEI (vs no-use) was associated with lower risk of CKD progression.

Endothelial-derived hyperpolarization contributes to acetylcholine-mediated vasodilation in human skin in a dose-dependent manner

Cutaneous acetylcholine (ACh)-mediated dilation is commonly used to assess microvascular function, but the mechanisms of dilation are poorly understood. Depending on dose and method of administration, nitric oxide (NO) and prostanoids are involved to varying extents and the roles of endothelial-derived hyperpolarizing factors (EDHFs) are unclear. In the present study, five incremental doses of ACh (0.01-100 mM) were delivered either as a 1-min bolus (protocol 1, n = 12) or as a ≥20-min continuous infusion (protocol 2, n = 10) via microdialysis fibers infused with 1) lactated Ringer, 2) tetraethylammonium (TEA) [a calcium-activated potassium channel (KCa) and EDHF inhibitor], 3) L-NNA+ketorolac [NO synthase (NOS) and cyclooxygenase (COX) inhibitors], and 4) TEA+L-NNA+Ketorolac. The hyperemic response was characterized as peak and area under the curve (AUC) cutaneous vascular conductance (CVC) for bolus infusions or plateau CVC for continuous infusions, and reported as %maximal CVC. In protocol 1, TEA, alone and combined with NOS+COX inhibition, attenuated peak CVC (100 mM Ringer 59 ± 6% vs. TEA 43 ± 5%, P < 0.05; L-NNA+ketorolac 35 ± 4% vs. TEA+L-NNA+ketorolac 25 ± 4%, P < 0.05) and AUC (Ringer 25,414 ± 3,528 vs. TEA 21,403 ± 3,416%·s, P < 0.05; L-NNA+ketorolac 25,628 ± 3,828%(.)s vs. TEA+L-NNA+ketorolac 20,772 ± 3,711%·s, P < 0.05), although these effects were only significant at the highest dose of ACh. At lower doses, TEA lengthened the total time of the hyperemic response (10 mM Ringer 609 ± 78 s vs. TEA 860 ± 67 s, P < 0.05). In protocol 2, TEA alone did not affect plateau CVC, but attenuated plateau in combination with NOS+COX inhibition (100 mM 50.4 ± 6.6% vs. 30.9 ± 6.3%, P < 0.05). Therefore, EDHFs contribute to cutaneous ACh-mediated dilation, but their relative contribution is altered by the dose and infusion procedure.

Endothelial dysfunction and increased responses to renal nerve stimulation in rat kidneys during rhabdomyolysis-induced acute renal failure: role of hydroxyl radical

Rhabdomyolysis is an important cause of acute renal failure (ARF) and renal vasoconstriction is the main mechanism in the pathogenesis of ARF. Lipid peroxidation due to hydroxyl radical (.OH) formation and redox cycling of myoglobin also have a role. We investigated the disturbance in renal vascular reactivity to reveal the mechanisms leading to ARF. Female Wistar rats (n = 7) were injected with glycerol (10 mL/kg, 50% in saline) intramuscularly to induce rhabdomyolysis, and then the kidneys were isolated and perfused. We investigated acetylcholine (ACh)-induced endothelium-dependent and papaverine (PAP)-induced endothelium-independent vasodilation responses and renal nerve stimulation (RNS)-induced vasoconstrictions. These were also investigated both in rats which received either .OH scavenger, dimethylthiourea (DMTU: 500 mg/kg before glycerol injection and 125 mg/kg 8 h after glycerol injection, n = 7), or myoglobin redox cycling inhibitor, acetaminophen (ApAP: 100 mg/kg 2 h before glycerol injection and 100 mg/kg each 4 h, and 22 h after glycerol injection, n = 7). ACh-induced responses in glycerol group were decreased (p < 0.001), but PAP-induced vasodilation did not change. RNS-induced vasoconstriction in all kidneys was greater (p < 0.001) in glycerol group. DMTU restored both endothelium-dependent vasodilation and RNS-induced vasoconstriction. ApAP had no effect on vascular responses. Both DMTU and ApAP exerted a partial protective effect in renal histology without restoring serum creatinine and blood urea nitrogen (BUN) levels or creatinine clearance. This study showed that endothelial dysfunction and increased vasoconstriction developed during rhabdomyolysis. .OH plays an important role in the development of these vascular responses. These findings suggest that decreased endothelium-dependent vasodilation and augmented renal sympathetic tonus contribute to the development of renal vasoconstriction during rhabdomyolysis-induced ARF.

Gender-specific effects of calcitonin gene-related peptide and substance P on coronary blood flow in an experimental model

BACKGROUND

Calcitonin gene-related peptide (CGRP) and substance P (SP) play counter-regulatory roles in coronary flow. This study is to assess whether effects of CGRP and SP are gender-specific.

METHODS

Langendorff-perfused hearts were used to compare coronary flow rates among 119 wild-type, alpha-CGRP and SP receptor knockout mice under various perfusion pressures (20, 30, 40, 50 mmHg).

RESULTS

For mouse heart coronary flow rate, deletion of alpha-CGRP gene resulted in significant reduction for both genders at all pressures; female CGRP knockout showed 15.3% reduction (P < .01); male CGRP knockout showed 13.8% reduction (P < .01); no significant difference between male and female CGRP knockout; female SP receptor knockout showed 13.9% increase (P < .01); female SP receptor knockout had a greater percentage decrease than male (P < .01).

CONCLUSIONS

CGRP plays similar roles as a vasodilator in males and females. SP seems to act as a vasoconstrictor in females.