Sarabdeep Singh

Maternal Inflammation Results in Altered Tryptophan Metabolism in Rabbit Placenta and Fetal Brain

Maternal inflammation has been linked to neurodevelopmental and neuropsychiatric disorders such as cerebral palsy, schizophrenia, and autism. We had previously shown that intrauterine inflammation resulted in a decrease in serotonin, one of the tryptophan metabolites, and a decrease in serotonin fibers in the sensory cortex of newborns in a rabbit model of cerebral palsy. In this study, we hypothesized that maternal inflammation results in alterations in tryptophan pathway enzymes and metabolites in the placenta and fetal brain. We found that intrauterine endotoxin administration at gestational day 28 (G28) resulted in a significant upregulation of indoleamine 2,3-dioxygenase (IDO) in both the placenta and fetal brain at G29 (24 h after treatment). This endotoxin-mediated IDO induction was also associated with intense microglial activation, an increase in interferon gamma expression, and increases in kynurenine and the kynurenine pathway metabolites kynurenine acid and quinolinic acid, as well as a significant decrease in 5-hydroxyindole acetic acid (a precursor of serotonin) levels in the periventricular region of the fetal brain. These results indicate that maternal inflammation shunts tryptophan metabolism away from the serotonin to the kynurenine pathway, which may lead to excitotoxic injury along with impaired development of serotonin-mediated thalamocortical fibers in the newborn brain. These findings provide new targets for prevention and treatment of maternal inflammation-induced fetal and neonatal brain injury leading to neurodevelopmental disorders such as cerebral palsy and autism.

Trajectory of inflammatory and microglial activation markers in the postnatal rabbit brain following intrauterine endotoxin exposure

BACKGROUND Maternal infection is a risk factor for periventricular leukomalacia and cerebral palsy (CP) in neonates. We have previously demonstrated hypomyelination and motor deficits in newborn rabbits, as seen in patients with cerebral palsy, following maternal intrauterine endotoxin administration. This was associated with increased microglial activation, primarily involving the periventricular region (PVR). In this study we hypothesized that maternal intrauterine inflammation leads to a pro-inflammatory environment in the PVR that is associated with microglial activation in the first 2 postnatal weeks. METHODS Timed pregnant New Zealand white rabbits underwent laparotomy on gestational day 28 (G28). They were randomly divided to receive lipopolysaccharide (LPS; 20μg/kg in 1mL saline) (Endotoxin group) or saline (1mL) (control saline, CS group), administrated along the wall of the uterus. The PVR from the CS and Endotoxin kits were harvested at G29 (1day post-injury), postnatal day1 (PND1, 3day post-injury) and PND5 (7days post-injury) for real-time PCR, ELISA and immunohistochemistry. Kits from CS and Endotoxin groups underwent longitudinal MicroPET imaging, with [11C]PK11195, a tracer for microglial activation. RESULTS We found that intrauterine endotoxin exposure resulted in pro-inflammatory microglial activation in the PVR of rabbits in the first postnatal week. This was evidenced by increased TSPO (translocator protein) expression co-localized with microglia/macrophages in the PVR, and changes in the microglial morphology (ameboid soma and retracted processes). In addition, CD11b level significantly increased with a concomitant decline in the CD45 level in the PVR at G29 and PND1. There was a significant elevation of pro-inflammatory cytokines and iNOS, and decreased anti-inflammatory markers in the Endotoxin kits at G29, PND1 and PND5. Increased [11C]PK11195 binding to the TSPO measured in vivo by PET imaging in the brain of Endotoxin kits was present up to PND14-17. CONCLUSIONS Our results indicate that a robust pro-inflammatory microglial phenotype/brain milieu commenced within 24h after LPS exposure and persisted through PND5 and in vivo TSPO binding was found at PND14-17. This suggests that there may be a window of opportunity to treat after birth. Therapies aimed at inducing an anti-inflammatory phenotype in microglia might promote recovery in maternal inflammation induced neonatal brain injury.

The Effects of Hemodynamic Changes on Pulse Wave Velocity in Cardiothoracic Surgical Patients

The effect of blood pressure on pulse wave velocity (PWV) is well established. However, PWV variability with acute hemodynamic changes has not been examined in the clinical setting. The aim of the present study is to investigate the effect of hemodynamic changes on PWV in patients who undergo cardiothoracic surgery. Using data from 25 patients, we determined blood pressure (BP), heart rate (HR), and the left ventricular outflow tract (LVOT) velocity-time integral. By superimposing the radial arterial waveform on the continuous wave Doppler waveform of the LVOT, obtained by transesophageal echo, we were able to determine pulse transit time and to calculate PWV, stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR). Increases in BP, HR, and SVR were associated with higher values for PWV. In contrast increases in SV were associated with decreases in PWV. Changes in CO were not significantly associated with PWV.

Perioperative hypothermia in neonatal intensive care unit patients: effectiveness of a thermoregulation intervention and associated risk factors

Hypothermia in neonatal intensive care unit patients is associated with morbidity. Perioperative normothermia is the standard of care.

Thermal QST Phenotypes Associated with Response to Lumbar Epidural Steroid Injections: A Pilot Study

Objective Response to lumbar epidural steroid injection in lumbar radicular pain varies. The purpose of this study is to characterize the changes in quantitative sensory testing (QST) phenotypes of subjects and compare the QST characteristics in patients who do respond to treatment of radicular pain with a lumbar epidural steroid injection (ESI). Design Prospective, observational pilot study. Setting Outpatient pain center. Methods Twenty subjects with a lower extremity (LE) radicular pain who were scheduled to have an ESI were recruited. At the visit prior to and four weeks following an ESI, subjects underwent QST measurements of both the affected LE and the contralateral unaffected UE. Results Following an ESI, nine subjects reported a greater than 30% reduction in radicular pain and 11 reported a less than 30% reduction in radicular pain. Subjects who had less than 30% pain reduction response (nonresponders) to an ESI had increased pre-injection warm sensation threshold (37.30 °C, SD = 2.51 vs 40.39, SD = 3.36, P = 0.03) and heat pain threshold (47.22 °C, SD = 1.38, vs 48.83 °C, SD = 2.10, P = 0.04). Further, the nonresponders also showed increased pre-injection warm sensation threshold as measured in the difference of warm sensation detection threshold difference in the affected limb and the unaffected arm (2.68 °C, SD = 2.92 vs 5.67 °C, SD = 3.22, P  = 0.045). Other QST parameters were not affected. Conclusions The results show that the nonresponders to ESIs have increased detection threshold to heat pain and warm sensation, suggesting that a preexisting dysfunction in the C fibers in this group of subjects who can be detected by QST. Such altered QST characteristics may prognosticate the response to ESIs.

Ejection time: Influence of hemodynamics and site of measurement in the arterial tree

The left ventricular ejection time is routinely measured from a peripheral arterial waveform. However, the arterial waveform undergoes constant transformation as the pulse wave propagates along the arterial tree. Our goal was to determine if the left ventricular ejection time measured peripherally in the arterial tree accurately reflected the ejection time measured through the aortic valve. Moreover, we examined/accessed the modulating influence of hemodynamics on ejection time measurements. Continuous wave Doppler waveform images through the aortic valve and the simultaneously obtained radial artery pressure waveforms were analyzed to determine central and peripheral ejection times, respectively. The peripheral ejection time was significantly longer than the simultaneously measured central ejection time (174.5±25.2 ms vs. 120.7±14.4 ms; P<0.0001; 17.4±8.7% increase). Moreover, the ejection time prolongation was accentuated at lower blood pressures, lower heart rate and lower pulse wave velocity. The time difference between centrally and peripherally measured ejection times likely reflects intrinsic vascular characteristics. Moreover, given that the ejection time also depends on blood pressure, heart rate and pulse wave velocity, peripherally measured ejection times might need to be adjusted to account for changes in these variables.

Anti-aging factor, serum alpha-Klotho, as a marker of acute physiological stress, and a predictor of ICU mortality, in patients with septic shock

Purpose: Genetic deletions decreasing serum alpha‐Klotho (alpha‐KL) have been associated with rapid aging, multi‐organ failure and increased mortality in experimental sepsis. We hypothesized that lower alpha‐KL obtained at the onset of septic shock correlates with higher mortality. Materials and methods: Prospective cohort of 104 adult patients with septic shock. Alpha‐KL was measured via ELISA on serum collected on the day of enrollment (within 72 h from the onset of shock). Relationship between alpha‐KL and clinical outcome measures was evaluated in uni‐ and multi‐variable models. Results: Median (IQR) alpha‐KL was 816 (1020.4) pg/mL and demonstrated a bimodal distribution with two distinct populations, Cohort A [n = 97, median alpha‐KL 789.3 (767.1)] and Cohort B [n = 7, median alpha‐KL 4365.1(1374.4), >1.5 IQR greater than Cohort A]. Within Cohort A, ICU non‐survivors had significantly higher serum alpha‐KL compared to survivors as well as significantly higher APACHE II and SOFA scores, rates of mechanical ventilation, and serum BUN, creatinine, calcium, phosphorus and lactate (all p ≤ 0.05). Serum alpha‐KL ≥ 1005, the highest tertile, was an independent predictor of ICU mortality when controlling for co‐variates (p = 0.028, 95% CI 1.143–11.136). Conclusions: Elevated serum alpha‐KL in patients with septic shock is independently associated with higher mortality. Further studies are needed to corroborate these findings.