Effect of exogenous glutamate and N-Methyl-D-aspartic acid on spontaneous activity of isolated human ureter

Profile of liver cholestatic biomarkers following prolonged ketamine administration in patients with COVID-19

BACKGROUND

To investigate the possible influence of prolonged ketamine (K) or esketamine (ESK) infusion on the profile of liver cholestatic biomarkers in patients with COVID-19 infection.

METHODS

A retrospective analysis was performed on 135 patients with COVID-19 related ARDS who received prolonged K or ESK infusion. They were compared to 15 COVID-19 ICU patients who did not receive K/ESK while being mechanically ventilated and 108 COVID-19 patients who did not receive mechanical ventilation nor K/ESK. The profile of the liver function tests was analysed in the groups.

RESULTS

Peak values of ALP, GGT and bilirubin were higher in the K/ESK group, but not for AST and ALT. Peak values of ALP were significantly higher among patients who underwent mechanical ventilation and who received K/ESK, compared with mechanically ventilated patients who did not receive K/ESK. There was a correlation between these peak values and the cumulative dose and duration of K/ESK therapy.

CONCLUSIONS

Based on the observations of biliary anomalies in chronic ketamine abusers, prolonged exposure to ketamine sedation during mechanical ventilation may also be involved, in addition to viral infection causing secondary sclerosing cholangitis. The safety of prolonged ketamine sedation on the biliary tract requires further investigations.

Risk of Renal Function Decline in Patients with Ketamine-Associated Uropathy

Ketamine-associated diseases have been increasing with the rise in ketamine abuse. Ketamine-associated uropathy is one of the most common complications. We investigated the effects of ketamine-associated uropathy on renal health and determined predictors of renal function decline in chronic ketamine abusers. This retrospective cohort study analyzed 51 patients (22 with ketamine-associated hydronephrosis and 29 with ketamine cystitis) from Kaohsiung Veterans General Hospital in Taiwan. Primary renal outcome was end-stage renal disease or estimated glomerular filtration rate decline >30% from baseline. Compared with the ketamine cystitis group, the hydronephrosis group had lower initial and final estimated glomerular filtration rates and higher alkaline phosphatase and gamma-glutamyl transferase levels (p < 0.05). Elevated cholestatic liver enzyme levels correlated with renal dysfunction in ketamine-associated uropathy. The hydronephrosis group had a higher proportion of patients reaching endpoints than the ketamine cystitis group (50% and 7%, respectively, p < 0.001). After adjusting for age, sex, and initial serum creatinine level, hydronephrosis remained an independent risk factor for renal function deterioration. Ketamine-associated hydronephrosis was a poor renal outcome and strong predictor of renal function decline in chronic ketamine abusers. Elevated cholestatic liver enzyme levels correlated with the severity of ketamine-associated uropathy. Ultrasonography screening of these high-risk groups and regular renal function follow-ups are necessary.

Liver injury is common among chronic abusers of ketamine

Abuse of ketamine leads to liver injury. We investigated the histopathologic and radiologic features of ketamine abusers with significant liver injury in a cross-sectional survey of 297 consecutive chronic abusers of ketamine with urinary tract dysfunction. Liver biopsy and magnetic resonance cholangiopancreatography were performed in patients with liver injury (concentrations of bilirubin, alkaline phosphatase, and/or alanine aminotransferase >2-fold the upper limit of normal). The prevalence of liver injury was 9.8% (all cases cholestatic). Bile duct injury was observed in all 7 patients assessed by liver biopsy. Two patients had bridging fibrosis despite their young age. Three of 6 patients who underwent magnetic resonance cholangiopancreatography examination were found to have prominent or dilated common bile ducts without obstructions or extrinsic compressions. Ketamine abuse therefore appears to lead to common bile duct dilatation, microscopic bile duct injury, and even significant liver fibrosis.

Regulation of airway contractility by plasminogen activators through N-methyl-D-aspartate receptor-1

Reactive airway disease is mediated by smooth muscle contraction initiated through several agonist-dependent pathways. Activation of type 1 N-methyl-D-aspartate receptors (NMDA-R1s) by plasminogen activators (PAs) has been linked to control of vascular tone, but their effect on airway smooth muscle contractility has not previously been studied to our knowledge. We observed that NMDA-R1s are expressed by human airway smooth muscle cells and constitutively inhibit the contraction of isolated rat tracheal rings in response to acetylcholine (Ach). Both tissue-type PA (tPA) and urokinase-type PA (uPA) bind to NMDA-R1 and reverse this effect, thereby enhancing Ach-induced tracheal contractility. Tracheal contractility initiated by Ach is reduced in rings isolated from tPA(-/-) and uPA(-/-) mice compared with their wild-type counterparts. The procontractile effect of uPA or tPA was mimicked and augmented by the nitric oxide synthase inhibitor, l-NAME. uPA and tPA further enhanced the contractility of rings denuded of epithelium, an effect that was inhibited by the NMDA-R antagonist, MK-801. Binding of PAs to NMDA-R1 and the subsequent activation of the receptor were inhibited by PA inhibitor type 1, by a PA inhibitor type 1-derived hexapeptide that recognizes the tPA and uPA docking domains, as well as by specific mutations within the docking site of tPA. These studies identify involvement of PAs and NMDA-R1 in airway contractility, and define new loci that could lead to the development of novel interventions for reactive airway disease.

Effects of exogenous glutamate and kainate on electric field-stimulated contractions of isolated human ureter

OBJECTIVES

A neurotransmitter role for glutamate in the autonomous nervous system was recently demonstrated in the gastrointestinal tract, and its stimulatory effect on spontaneous motility of human ureter was shown. The aim of our study was to investigate the effects of glutamate on the release of neurotransmitters from intramural nerves of the human ureter.

METHODS

The effects of exogenous glutamate were tested on electric field-stimulated contractions of isolated human ureter, taken from 16 adult patients after nephrectomy. The longitudinal tension and intraluminal pressure of the isolated ureter were recorded simultaneously. The electric field stimulation was done with square wave pulses (20 V through electrodes, 400 mA, duration 1 ms, frequency 16 Hz). The pulse trains lasted for 30 s, a with 30-s pause.

RESULTS

Glutamate (7.9 x 10(-6) M/L to 10.6 x 10(-3) M/L) and kainic acid (6.3 x 10(-8) M/L to 2.2 x 10(-5) M/L) produced a concentration-dependent decrease in the electric field-stimulated activity of the isolated preparations. However, N-methyl-D-aspartic acid (9.1 x 10(-8) M/L to 3.1 x 10(-5) M/L), (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (7.2 x 10(-8) M/L to 3.2 x 10(-6) M/L) and (+/-)-1-Aminocyclopentane-trans-1,3-dicarboxylic acid (7.7 x 10(-8) M/L to 6.5 x 10(-5) M/L) were ineffective. The electric field-stimulated contractions of isolated ureter were also inhibited by lidocaine (3.70 x 10(-4)M/L) and atropine (1.00 x 10(-6)M/L).

CONCLUSIONS

The results of our study suggest that glutamate inhibits electric field-stimulated release of acetylcholine in the human ureter through activation of kainate ionotropic receptors, located on the intramural nerve fibers.