Fingerprint of Circulating Immunocytes as Biomarkers for the Prognosis of Brain Inflammation and Neuronal Injury after Cardiac Arrest.

Cardiac arrest is one of the most dangerous health problems in the world. Outcome prognosis is largely based on cerebral performance categories determined by neurological evaluations. Few systemic tests are currently available to predict survival to hospital discharge. Here, we present the results from the preclinical studies of cardiac arrest and resuscitation (CAR) in mice to identify signatures of circulating immune cells as blood-derived biomarkers to predict outcomes after CAR. Two flow cytometry panels for circulating blood lymphocytes and myeloid-derived cells, respectively, were designed to correlate with neuroinflammation and neuronal and dendritic losses in the selectively vulnerable regions of bilateral hippocampi. We found that CD4+CD25+ regulatory T cells, CD11b+CD11c- and CD11b+Ly6C+Ly6G+ myeloid-derived cells, and cells positive for the costimulatory molecules CD80 and CD86 in the blood were correlated with activation of microglia and astrocytosis, and CD4+CD25+ T cells are additionally correlated with neuronal and dendritic losses. A fingerprint pattern of blood T cells and monocytes is devised as a diagnostic tool to predict CAR outcomes. Blood tests aimed at identifying these immunocyte patterns in cardiac arrest patients will guide future clinical trials to establish better prognostication tools to avoid unnecessary early withdrawal from life-sustaining treatment.

A Thermal Place Preference Test for Discovery of Neuropathic Pain Drugs.

Developing potent non-opioid pain medications is an integral part of the battle to conquer both chronic pain and the current opioid crisis. Although most screening approaches use in vitro surrogate targets, in vivo screening of analgesic candidates is a necessary preclinical step in drug discovery. Here, we report the design of a new automated behavioral testing apparatus based on the principle of a thermal place preference test (TPPT). This new design can detect, quantify, and differentiate behavioral responses to cold stimuli between sham and chronic constriction injury (CCI) rodents with up to 12 animals tested simultaneously. At an optimized temperature pair of 12.5 °C vs 30.0 °C (±0.5 °C), the TPPT design has captured the antinociceptive effects of morphine and pregabalin on CCI rats in individual 10 min tests. Moreover, it can differentiate analgesic effects by morphine or pregabalin from anxiolytic effects by diazepam. The results, along with the relatively low cost to construct the apparatus and moderately high throughput, make our TPPT design applicable for behavioral studies of chronic pain in rodents and for high-throughput in vivo screening of the next generation of pain medications.

Invasion of Peripheral Immune Cells into Brain Parenchyma after Cardiac Arrest and Resuscitation.

Although a direct link has long been suspected between systemic immune responses and neuronal injuries after stroke, it is unclear which immune cells play an important role. A question remains as to whether the blood brain barrier (BBB) is transiently disrupted after circulatory arrest to allow peripheral immune cells to enter brain parenchyma. Here, we developed a clinically relevant cardiac arrest and resuscitation model in mice to investigate the BBB integrity using noninvasive magnetic resonance imaging. Changes in immune signals in the brain and periphery were assayed by immunohistochemistry and flow cytometry. Quantitative variance maps from T1-weighted difference images before and after blood-pool contrast clearance revealed BBB disruptions immediately after resuscitation and one day after reperfusion. Time profiles of hippocampal CA1 neuronal injuries correlated with the morphological changes of microglia activation. Cytotoxic T cells, CD11b+CD11c+ dendritic cells, and CD11b+CD45+hi monocytes and macrophages were significantly increased in the brain three days after cardiac arrest and resuscitation, suggesting direct infiltration of these cells following the BBB disruption. Importantly, these immune cell changes were coupled with a parallel increase in the same subset of immune cell populations in the bone marrow and blood. We conclude that neurovascular breakdown during the initial reperfusion phase contributes to the systemic immune cell invasion and subsequent neuropathogenesis affecting the long-term outcome after cardiac arrest and resuscitation.