Selective Activation of Basal Forebrain Cholinergic Neurons Attenuates Polymicrobial Sepsis-Induced Inflammation via the Cholinergic Anti-Inflammatory Pathway

Electrical stimulation of the dorsal motor nucleus of the vagus in male mice can regulate inflammation without affecting the heart rate

BACKGROUND

The vagus nerve plays an important role in neuroimmune interactions and in the regulation of inflammation. A major source of efferent vagus nerve fibers that contribute to the regulation of inflammation is the brainstem dorsal motor nucleus of the vagus (DMN), as recently shown using optogenetics. In contrast to optogenetics, electrical neuromodulation has broad therapeutic implications. However, the anti-inflammatory effectiveness of electrical stimulation of the DMN (eDMNS) and the possible heart rate (HR) alterations associated with this approach have not been investigated. Here, we examined the effects of eDMNS on HR and cytokine levels in mice administered with lipopolysaccharide (LPS, endotoxin) and in mice subjected to cecal ligation and puncture (CLP) sepsis.

METHODS

Anesthetized male 8-10-week-old C57BL/6 mice on a stereotaxic frame were subjected to eDMNS using a concentric bipolar electrode inserted into the left or right DMN or sham stimulation. eDMNS (500, 250 or 50 μA at 30 Hz, for 1 min) was performed and HR recorded. In endotoxemia experiments, sham or eDMNS utilizing 250 μA or 50 μA was performed for 5 mins and was followed by LPS (0.5 mg/kg) i.p. administration. eDMNS was also applied in mice with cervical unilateral vagotomy or sham operation. In CLP experiments sham or left eDMNS was performed immediately post CLP. Cytokines and corticosterone were analyzed 90 mins after LPS administration or 24 h after CLP. CLP survival was monitored for 14 days.

RESULTS

Either left or right eDMNS at 500 μA and 250 μA decreased HR, compared with baseline pre-stimulation. This effect was not observed at 50 μA. Left side eDMNS at 50 μA, compared with sham stimulation, significantly decreased serum and splenic levels of the pro-inflammatory cytokine TNF and increased serum levels of the anti-inflammatory cytokine IL-10 during endotoxemia. The anti-inflammatory effect of eDMNS was abrogated in mice with unilateral vagotomy and was not associated with serum corticosterone alterations. Right side eDMNS in endotoxemic mice suppressed serum TNF and increased serum IL-10 levels but had no effects on splenic cytokines. In mice with CLP, left side eDMNS suppressed serum IL-6, as well as splenic IL-6 and increased splenic IL-10 and significantly improved the survival rate of CLP mice.

CONCLUSIONS

For the first time we show that a regimen of eDMNS which does not cause bradycardia alleviates LPS-induced inflammation. These eDMNS anti-inflammatory effects require an intact vagus nerve and are not associated with corticosteroid alterations. eDMNS also decreases inflammation and improves survival in a model of polymicrobial sepsis. These findings are of interest for further studies exploring bioelectronic anti-inflammatory approaches targeting the brainstem DMN.

Neuroinflammation in the medullary visceral zone exert a powerful impaction on the systemic inflammation in sepsis through cholinergic anti-inflammatory pathway

To investigate whether sepsis-induced neuroinflammation of medulla visceral zone (MVZ) predominates the systemic inflammation through cholinergic anti-inflammatory pathway (CAP), and to explore the effect of central anti-inflammation on systemic inflammation. 112 adult Sprague-Dawley male rats were randomly divided into sepsis experimental group (n = 56) and neuroinflammation experimental group (n = 56). The two experimental groups were individually randomly divided into control group (n = 8), model group (n = 16), central anti-inflammatory group (n = 16) and vagus transection group (n = 16). Rats in two control groups were administered with saline at the dose of 6 mL/kg intraperitoneally or with 25 μL artificial cerebrospinal fluid injected into forth ventricle once a day for 3 days. Rats in two model groups were administered with Lipopolysaccharide (LPS) at the dose of 6 mg/kg intraperitoneally or with 25 μg/25 μL LPS injected into forth ventricle once a day for 3 days. Rats in two central anti-inflammatory groups were fed with 10 mg/mL minocycline sucrose solution as the only water source for 4 days prior to be treated as the model groups of their own, and feeding style was continued until the end of the experiment. Rats in the two vagus transection groups were undergone right vagotomy and 7 days of adaptive feeding prior to be treated as the same as those in the central anti-inflammatory group of their own. The Murine Sepsis Score (MSS), mortality rate and heat rate variability (HRV) were recorded during the last 3 days of intervention. Then the rats were sacrificed and blood samples were collected for ELISA analysis to detect the serum level of inflammatory cytokines such as TNF-α, IL-6, and IL-10. The expression of TNF-α and IL-6 in medulla oblongata were analyzed by Western blot. The correlation and regression analysis among the expression levels of cytokines in medulla oblongata, HRV indexes and serum inflammatory cytokines were performed. The mortality rate and MSS of the sepsis model group and the MVZ's neuroinflammation model group were significantly higher than those of their own control group, and the central anti-inflammation reduced the mortality rate and MSS scores of the two model groups, while the right vagotomy abolished the effect of central anti-inflammatory. In the sepsis model group and the MVZ's neuroinflammation model group, the levels of TNF-α, IL-6, and other cytokines in serum and MVZ were significantly increased, and HRV indexes (SDNN, RMSSD, LF, HF, LF/HF) were significantly decreased (P = 0.000). Central anti-inflammatory treatment reversed the above changes. However, right vagotomy abolished the central anti-inflammatory effect. Correlation and regression analysis showed that there was a significant linear correlation among the expression of inflammatory factors in MVZ, the indexes of HRV and the levels of serum cytokines. Our study shows that sepsis-induced MVZ's neuroinflammation exert a powerful influence on the systemic inflammation through CAP in sepsis. Central anti-inflammation effectively improves systemic inflammation through inhibiting MVZ's neuroinflammation in sepsis. The time domain and frequency domain indexes of HRV can reflect the regulatory effect of CAP and the degree of inflammation of MVZ, which may be potentially used to monitor the condition and treatment effectiveness of sepsis patients.

Targeting blood-brain barrier for sepsis-associated encephalopathy: Regulation of immune cells and ncRNAs

Sepsis causes significant morbidity and mortality worldwide, most surviving patients show acute or chronic mental disorders, which are known as sepsis-associated encephalopathy (SAE). SAE involves many pathological processes, including the blood-brain barrier (BBB) damage. The BBB is located at the interface between the central nervous system and the surrounding environment, which protects the central nervous system (CNS) from the invasion of exogenous molecules, harmful substances or microorganisms in the blood. Recently, a growing number of studies have indicated that the BBB destruction was involved in SAE and played an important role in SAE-induced brain injury. In the present review, we firstly reveal the pathological processes of SAE such as the neurotransmitter disorders, oxidative stress, immune dysfunction and BBB destruction. Moreover, we introduce the structure of BBB, and describe the immune cells including microglia and astrocytes that participate in the BBB destruction after SAE. Furthermore, in view of the current research on non-coding RNAs (ncRNAs), we explain the regulatory mechanism of ncRNAs including long noncoding RNAs (lncRNAs), microRNAs (miRNAs) and circular RNAs (circRNAs) on BBB in the processes of SAE. Finally, we propose some challenges and perspectives of regulating BBB functions in SAE. Hence, on the basis of these effects, both immune cells and ncRNAs may be developed as therapeutic targets to protect BBB for SAE patients.

M1 cholinergic signaling in the brain modulates cytokine levels and splenic cell sub-phenotypes following cecal ligation and puncture

BACKGROUND

The contribution of the central nervous system to sepsis pathobiology is incompletely understood. In previous studies, administration of endotoxin to mice decreased activity of the vagus anti-inflammatory reflex. Treatment with the centrally-acting M1 muscarinic acetylcholine (ACh) receptor (M1AChR) attenuated this endotoxin-mediated change. We hypothesize that decreased M1AChR-mediated activity contributes to inflammation following cecal ligation and puncture (CLP), a mouse model of sepsis.

METHODS

In male C57Bl/6 mice, we quantified basal forebrain cholinergic activity (immunostaining), hippocampal neuronal activity, serum cytokine/chemokine levels (ELISA) and splenic cell subtypes (flow cytometry) at baseline, following CLP and following CLP in mice also treated with the M1AChR agonist xanomeline.

RESULTS

At 48 h. post-CLP, activity in basal forebrain cells expressing choline acetyltransferase (ChAT) was half of that observed at baseline. Lower activity was also noted in the hippocampus, which contains projections from ChAT-expressing basal forebrain neurons. Serum levels of TNFα, IL-1β, MIP-1α, IL-6, KC and G-CSF were higher post-CLP than at baseline. Post-CLP numbers of splenic macrophages and inflammatory monocytes, TNFα+ and ILβ+ neutrophils and ILβ+ monocytes were higher than baseline while numbers of central Dendritic Cells (cDCs), CD4+ and CD8+ T cells were lower. When, following CLP, mice were treated with xanomeline activity in basal forebrain ChAT-expressing neurons and in the hippocampus was significantly higher than in untreated animals. Post-CLP serum concentrations of TNFα, IL-1β, and MIP-1α, but not of IL-6, KC and G-CSF, were significantly lower in xanomeline-treated mice than in untreated mice. Post-CLP numbers of splenic neutrophils, macrophages, inflammatory monocytes and TNFα+ neutrophils also were lower in xanomeline-treated mice than in untreated animals. Percentages of IL-1β+ neutrophils, IL-1β+ monocytes, cDCs, CD4+ T cells and CD8+ T cells were similar in xanomeline-treated and untreated post-CLP mice.

CONCLUSION

Our findings indicate that M1AChR-mediated responses modulate CLP-induced alterations in serum levels of some, but not all, cytokines/chemokines and affected splenic immune response phenotypes.

Adenosine A1 receptors of the medullary solitary tract arbitrate the nicotine counteraction of neuroinflammation and cardiovascular dysfunction in septic rats

The cholinergic pathway plays a crucial role in improving inflammatory end-organ damage. Given the interplay between cholinergic and adenosinergic neurotransmission, we tested the hypothesis that central adenosine A1 receptors (A1ARs) modulate the nicotine counteraction of cardiovascular and inflammatory insults induced by sepsis in rats. Sepsis was induced by cecal ligation and puncture (CLP) 24-h before cardiovascular measurements. Nicotine (25-100 µg/kg i.v.) dose-dependently reversed septic manifestations of hypotension and impaired heart rate variability (HRV) and cardiac sympathovagal balance. Like nicotine, intracisternal (i.c.) administration of N(6)-cyclopentyladenosine (CPA, A1AR agonist) to CLP rats increased indices of HRV and sympathovagal balance. Moreover, greater surges in these parameters were noted upon simultaneous nicotine/CPA administration. The favorable influences of nicotine on blood pressure and HRV in sepsis were diminished after central blockade of A1ARs by i.c. 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX). Molecular studies revealed that (i) septic rises in myocardial and brainstem nucleus of solitary tract (NTS) NFκB expression were abrogated by nicotine and largely reinstated after blockade of A1ARs, and (ii) A1AR expression in the same areas was reduced by DPCPX. It is concluded that myocardial and medullary A1ARs facilitate the cholinergic counteraction of cardiac and neuroinflammation induced by sepsis and interrelated cardiomyopathic and neuropathic hitches.

M1 Cholinergic Signaling Modulates Cytokine Levels and Splenocyte Sub-Phenotypes Following Cecal Ligation and Puncture

Background

The contribution of the central nervous system to sepsis pathobiology is incompletely understood. In previous studies, administration of endotoxin to mice decreased activity of the vagus anti-inflammatory reflex. Treatment with the centrally-acting M1/M4 muscarinic acetylcholine (ACh) receptor (M1/M4AChR) attenuated this endotoxin-mediated change. We hypothesize that decreased M1/M4AChR-mediated activity contributes to inflammation following cecal ligation and puncture (CLP), a mouse model of sepsis.

Methods

Basal forebrain cholinergic activity (immunostaining), serum cytokine/chemokine levels (ELISA) and splenocyte subtypes (flow cytometry) were examined at baseline and following CLP in male C57BL/6 male mice.

Rersults

At 48hrs. post-CLP, activity in basal forebrain cells expressing choline acetyltransferase (ChAT) was half of that observed at baseline. Lower activity was also noted in the hippocampus, which contains projections from ChAT-expressing basal forebrain neurons. Serum levels of TNFα, IL-1β, MIP-1α, IL-6, KC and G-CSF were higher post-CLP than at baseline. Post-CLP numbers of splenic macrophages and inflammatory monocytes, TNFa+ and ILb+ neutrophils and ILb+ monocytes were higher than baseline while numbers of central Dendritic Cells (cDCs), CD4+ and CD8+ T cells were lower. When, following CLP, mice were treated with xanomeline, a central-acting M1AChR agonist, activity in basal forebrain ChAT-expressing neurons and in the hippocampus was significantly higher than in untreated animals. Post-CLP serum concentrations of TNFα, IL-1β, and MIP-1α, but not of IL-6, KC and G-CSF, were significantly lower in xanomline-treated mice than in untreated mice. Post-CLP numbers of splenic neutrophils, macrophages, inflammatory monocytes and TNFα+ neutrophils also were lower in xanomeline-treated mice than in untreated animals. The effects of CLP on percentages of IL-1β+ neutrophils, IL-1β+ monocytes, cDCs, CD4+ T cells and CD8+ T cells were similar in xanomeline - treated and untreated post-CLP mice.

Conclusion

Our findings indicate that M1/M4AChR-mediated responses modulate CLP-induced alterations in the distribution of some, but not all, leukocyte phenotypes and certain cytokines and chemokines.

Optogenetic stimulation of basal forebrain cholinergic neurons prevents neuroinflammation and neuropsychiatric manifestations in pristane induced lupus mice

BACKGROUND

Neuroinflammation has been identified as one of the primary pathogenic factors of neuropsychiatric systemic lupus erythematosus (NPSLE). However, there are no dedicated treatments available in clinics to alleviate neuroinflammation in NPSLE. It has been proposed that stimulating basal forebrain (BF) cholinergic neurons may provide potent anti-inflammatory effects in several inflammatory diseases, but its potential role in NPSLE remains unexplored. This study aims to investigate whether and how stimulating BF cholinergic neurons has a protective effect on NPSLE.

RESULTS

Optogenetic stimulation of BF cholinergic neurons significantly ameliorated olfactory dysfunction and anxiety- and depression-like phenotype in pristane induced lupus (PIL) mice. The increased expression of adhesion molecules (P-selectin and vascular cell adhesion molecule-1 (VCAM-1)), leukocyte recruitment, blood-brain barrier (BBB) leakage were significantly decreased. Notably, the brain histopathological changes, including the elevated levels of pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β), IgG deposition in the choroid plexus and lateral ventricle wall and lipofuscin accumulation in the cortical and hippocampal neurons, were also significantly attenuated. Furthermore, we confirmed the colocalization between the BF cholinergic projections and the cerebral vessels, and the expression of α7-nicotinic acetylcholine receptor (α7nAChR) on the cerebral vessels.

CONCLUSION

Our data indicate that stimulation of BF cholinergic neurons could play a neuroprotective role in the brain through its cholinergic anti-inflammatory effects on cerebral vessels. Therefore, this may be a promising preventive target for NPSLE.

Electrical stimulation of the dorsal motor nucleus of the vagus regulates inflammation without affecting the heart rate

Background

The vagus nerve plays an important role in neuroimmune interactions and in the regulation of inflammation. A major source of efferent vagus nerve fibers that contribute to the regulation of inflammation is the brainstem dorsal motor nucleus of the vagus (DMN) as recently shown using optogenetics. In contrast to optogenetics, electrical neuromodulation has broad therapeutic implications, but the anti-inflammatory efficacy of electrical DMN stimulation (eDMNS) was not previously investigated. Here, we examined the effects of eDMNS on heart rate (HR) and cytokine levels in murine endotoxemia as well as the cecal ligation and puncture (CLP) model of sepsis.

Methods

Anesthetized male 8-10-week-old C57BL/6 mice on a stereotaxic frame were subjected to eDMNS using a concentric bipolar electrode inserted into the left or right DMN or sham stimulation. eDMNS (50, 250 or 500 μA and 30 Hz, for 1 min) was performed and HR recorded. In endotoxemia experiments, sham or eDMNS utilizing 250 μA or 50 μA was performed for 5 mins and was followed by LPS (0.5 mg/kg) i.p. administration. eDMNS was also applied in mice with cervical unilateral vagotomy or sham operation. In CLP experiments sham or left eDMNS was performed immediately post CLP. Cytokines and corticosterone were analyzed 90 mins after LPS administration or 24h after CLP. CLP survival was monitored for 14 days.

Results

Either left or right eDMNS at 250 μA and 500 μA decreased HR, compared with pre- and post-stimulation. This effect was not observed at 50 μA. Left side eDMNS at 50 μA, compared with sham stimulation, significantly decreased serum and splenic levels of the pro-inflammatory cytokine TNF and increased serum levels of the anti-inflammatory cytokine IL-10 during endotoxemia. The anti-inflammatory effect of eDMNS was abrogated in mice with unilateral vagotomy and were not associated with serum corticosterone alterations. Right side eDMNS suppressed serum TNF levels but had no effects on serum IL-10 and on splenic cytokines. In mice with CLP, left side eDMNS suppressed serum TNF and IL-6, as well as splenic IL-6 and increased splenic IL-10 and significantly improved the survival rate of CLP mice.

Conclusions

For the first time we show that a regimen of eDMNS which does not cause bradycardia alleviates LPS-induced inflammation and these effects require an intact vagus nerve and are not associated with corticosteroid alterations. eDMNS also decreases inflammation and improves survival in a model of polymicrobial sepsis. These findings are of interest for further studies exploring bioelectronic anti-inflammatory approaches targeting the brainstem DMN.

Selective activation of cholinergic neurotransmission from the medial septal nucleus to hippocampal pyramidal neurones improves sepsis-induced cognitive deficits in mice

BACKGROUND

Sepsis-associated encephalopathy is characterised by cognitive dysfunction, and might be mediated by deficits in neurotransmission. Reduced cholinergic neurotransmission in the hippocampus impairs memory function. We assessed real-time alterations of acetylcholine neurotransmission from the medial septal nucleus to the hippocampus, and explored whether sepsis-induced cognitive deficits can be relieved by activating upstream cholinergic projections.

METHOD

Lipopolysaccharide (LPS) injection or caecal ligation and puncture (CLP) was used to induce sepsis and associated neuroinflammation in wild-type and mutant mice. Adeno-associated viruses for calcium and acetylcholine imaging, and for optogenetic and chemogenetic modulation of cholinergic neurones were injected into the hippocampus or medial septum, and a 200-μm-diameter optical fibre was implanted to collect acetylcholine and calcium signals. Cholinergic activity of the medial septum was manipulated and combined with cognitive assessment after LPS injection or CLP.

RESULTS

Intracerebroventricular LPS injection reduced postsynaptic acetylcholine (from 0.146 [0.001] to 0.0047 [0.0005]; p=0.004) and calcium (from 0.0236 [0.0075] to 0.0054 [0.0026]; p=0.0388) signals in hippocampal Vglut2-positive glutamatergic neurones, whereas optogenetic activation of cholinergic neurones in the medial septum reversed LPS-induced reductions in these two signals. Intraperitoneal LPS injection decreased acetylcholine concentration in the hippocampus (476 [20] pg ml^-1 to 382 [14] pg ml^-1; p=0.0001). Reduction in long-term potentiation (238 [23] % to 150 [12] %; p=0.0082) and enhancement of hippocampal pyramidal neurone action potential frequency (5.8 [1.5] Hz to 8.2 [1.8] Hz; p=0.0343) were relieved, and neurocognitive performance was improved by chemogenetic activation of cholinergic innervation of the hippocampus 3 days after LPS injection in septic mice.

CONCLUSIONS

Systemic or local LPS reduced cholinergic neurotransmission from the medial septum to hippocampal pyramidal neurones, and their selective activation alleviated defects in hippocampal neuronal function and synaptic plasticity and ameliorated memory deficits in sepsis model mice through enhanced cholinergic neurotransmission. This provides a basis for targeting cholinergic signalling to the hippocampus in sepsis-induced encephalopathy.

Can a basic solution activate the inflammatory reflex? A review of potential mechanisms, opportunities, and challenges

Stimulation of the inflammatory reflex (IR) is a promising strategy to treat systemic inflammatory disorders. However, this strategy is hindered by the cost and side effects of traditional IR activators. Recently, oral intake of sodium bicarbonate (NaHCO3) has been suggested to activate the IR, providing a safe and inexpensive alternative. Critically, the mechanisms whereby NaHCO3 might achieve this effect and more broadly the pathways underlying the IR remain poorly understood. Here, we argue that the recognition of NaHCO3 as a potential IR activator presents exciting clinical and research opportunities. To aid this quest, we provide an integrative review of our current knowledge of the neural and cellular pathways mediating the IR and discuss the status of physiological models of IR activation. From this vantage point, we derive testable hypotheses on potential mechanisms whereby NaHCO3 might stimulate the IR and compare NaHCO3 with classic IR activators. Elucidation of these mechanisms will help determine the therapeutic value of NaHCO3 as an IR activator and provide new insights into the IR circuitry.

Activation of basal forebrain cholinergic neurons improves colonic hyperpermeability through the vagus nerve and adenosine A2B receptors in rats

Intestinal barrier dysfunction, a leaky gut, contributes to the pathophysiology of various diseases such as dementia and irritable bowel syndrome (IBS). We recently clarified that orexin, ghrelin, or adenosine A2B signaling in the brain improved leaky gut through the vagus nerve. The present study was performed to clarify whether basal forebrain cholinergic neurons (BFCNs) are implicated in the central regulation of intestinal barrier function. We activated BFCNs using benzyl quinolone carboxylic acid (BQCA), a positive muscarinic M1 allosteric modulator, and evaluated colonic permeability by quantifying the absorbed Evans blue in rat colonic tissue. Intracisternal (not intraperitoneal) injection of BQCA blocked the increased colonic permeability in response to lipopolysaccharide. Vagotomy blocked BQCA-induced improvement of colonic hyperpermeability. Intracisternally administered pirenzepine, a muscarinic M1 selective antagonist, prevented intestinal barrier function improvement by intravenously administered 2-deoxy-d-glucose, central vagal stimulant. Adenosine A2B receptor antagonist but not dopamine or opioid receptor antagonist prevented BQCA-induced blockade of colonic hyperpermeability. Additionally, intracisternal injection of pirenzepine blocked orexin- or butyrate-induced intestinal barrier function improvement. These results suggest that BFCNs improve leaky gut through adenosine A2B signaling and the vagal pathway. Furthermore, BFCNs mediate orexin- or butyrate-induced intestinal barrier function improvement. Since BFCNs play a role in cognitive function and a leaky gut is associated with dementia, the present finding may lead us to speculate that BFCNs are involved in the development of dementia by regulating intestinal barrier function.

The Rostral Ventromedial and Lateral Medulla Are the Major Areas Responsive to Lung Cancer Progression among Brainstem Lung-Innervating Nuclei

In recent years, the information crosstalk between the central nervous system and the periphery has been a hot topic, such as the brain-gut axis, brain-lung axis, etc. Among them, some studies have shown that brainstem nuclei activity can significantly affect the progression of peripheral tumor; however, regarding lung cancer, our understanding of the basic characteristics of the lung-innervating brain nuclei responsive to lung cancer progression remains deficient. Therefore, we used the pseudorabies virus for retrograde labeling of nerves to study the neural circuits between the lung and brain. We then established a mouse orthotopic lung cancer model and used the expression of the c-Fos gene in brain regions to characterize activated brain circuits and compared these results with those of the control group. We focused on c-Fos activity in nuclei associated with retrograde tracing regions of the brainstem. We found over 16 nuclei in the whole brain with direct or indirect lung innervation through neural retrograde labeling with the pseudorabies virus. We further revealed that the neuronal activity of the rostral ventrolateral reticular nucleus (RVL), caudal nucleus of Raphe (raphe obscurus nucleus, ROb), Raphe pallidus nucleus (RPa), and ventral gigantocellular reticular nucleus (GiV) in the rostral ventromedial and lateral medulla were significantly changed in an orthotopic lung cancer mouse model by the immunostaining of c-Fos early responsive protein. Thus, the distinctive rostroventral medulla area, functionally closely related to the vagus nerve, likely plays a role in central neural interaction with peripheral lung tumors and deserves future investigation.

Sepsis-Induced Brain Dysfunction: Pathogenesis, Diagnosis, and Treatment

Dysregulated host response to infection, which cause life-threatening organ dysfunction, was defined as sepsis. Sepsis can cause acute and long-term brain dysfunction, namely, sepsis-associated encephalopathy (SAE) and cognitive impairment. SAE refers to changes in consciousness without direct evidence of central nervous system infection. It is highly prevalent and may cause poor outcomes in sepsis patients. Cognitive impairment seriously affects the life quality of sepsis patients and increases the medical burden. The pathogenesis of sepsis-induced brain dysfunction is mainly characterized by the interaction of systemic inflammation, blood-brain barrier (BBB) dysfunction, neuroinflammation, microcirculation dysfunction, and brain dysfunction. Currently, the diagnosis of sepsis-induced brain dysfunction is based on clinical manifestation of altered consciousness along with neuropathological examination, and the treatment is mainly involves controlling sepsis. Although treatments for sepsis-induced brain dysfunction have been tested in animals, clinical treat sepsis-induced brain dysfunction is still difficult. Therefore, we review the underlying mechanisms of sepsis-induced brain injury, which mainly focus on the influence of systemic inflammation on BBB, neuroinflammation, brain microcirculation, and the brain function, which want to bring new mechanism-based directions for future basic and clinical research aimed at preventing or ameliorating brain dysfunction.

Electroacupuncture Alleviates LPS-Induced ARDS Through α7 Nicotinic Acetylcholine Receptor-Mediated Inhibition of Ferroptosis

Acute respiratory distress syndrome (ARDS) is an uncontrollable, progressive pulmonary inflammatory disease, and as a common clinical critical disease, there is no effective treatment available. Electroacupuncture (EA) therapy is a type of traditional Chinese medicine physiotherapy that can alleviate the inflammatory response. However, the potential mechanism of EA in the treatment of ARDS is not yet clear. Ferroptosis is a new type of programmed cell death characterized by intracellular iron accumulation and lipid peroxidation. Recently, emerging evidence has shown that ferroptosis is closely related to the occurrence and development of ARDS caused by various pathological factors. Here, we further investigated whether EA-mediated inhibition of ferroptosis in lung tissue could attenuate lipopolysaccharide (LPS)-induced ARDS and explored its underlying mechanisms. In this study, mice were administered LPS intraperitoneally to establish a model of LPS-induced ARDS. We found that EA stimulation could not only reduce the exudation of inflammatory cells and proteins in the alveolar lumen but also significantly alleviate the pathological changes of lung tissue, inhibit the production of proinflammatory cytokines and improve the survival rate of mice. Concurrently, we also found that ferroptosis events occurred in the lung tissue of LPS-induced ARDS mice, manifested by elevated iron levels, ROS production and lipid peroxidation. Intriguingly, our results showed that EA stimulation at the Zusanli (ST36) acupoint activated α7 nicotinic acetylcholine receptor (α7nAchR) in lung tissue mainly through the sciatic nerve and cervical vagus nerve, thus exerting anti-ferroptosis and pulmonary protective effects. Additionally, these effects were eliminated by methyllycaconitine (MLA), a selective antagonist of α7nAchR. In vitro experiments, activation of α7nAchR protected alveolar epithelial cells from LPS-induced ferroptosis. Furthermore, our experiments showed that the pulmonary protective effects of EA stimulation were effectively reversed by erastin, a ferroptosis activator. Collectively, we demonstrated that EA stimulation could alleviate LPS-induced ARDS by activating α7nAchR to inhibit LPS-induced ferroptosis in alveolar epithelial cells. Targeting and regulating ferroptosis in alveolar epithelial cells may be a potential intervention approach for the treatment of LPS-induced ALI/ARDS in the future.

The Regulation Effect of α7nAChRs and M1AChRs on Inflammation and Immunity in Sepsis

The inflammatory storm in the early stage and immunosuppression in the late stage are responsible for the high mortality rates and multiple organ dysfunction in sepsis. In recent years, studies have found that the body's cholinergic system can spontaneously and dynamically regulate inflammation and immunity in sepsis according to the needs of the body. Firstly, the vagus nerve senses and regulates local or systemic inflammation by means of the Cholinergic Anti-inflammatory Pathway (CAP) and activation of α7-nicotinic acetylcholine receptors (α7nAChRs); thus, α7nAChRs play important roles for the central nervous system (CNS) to modulate peripheral inflammation; secondly, the activation of muscarinic acetylcholine receptors 1 (M1AChRs) in the forebrain can affect the neurons of the Medullary Visceral Zone (MVZ), the core of CAP, to regulate systemic inflammation and immunity. Based on the critical role of these two cholinergic receptor systems in sepsis, it is necessary to collect and analyze the related findings in recent years to provide ideas for further research studies and clinical applications. By consulting the related literature, we draw some conclusions: MVZ is the primary center for the nervous system to regulate inflammation and immunity. It coordinates not only the sympathetic system and vagus system but also the autonomic nervous system and neuroendocrine system to regulate inflammation and immunity; α7nAChRs are widely expressed in immune cells, neurons, and muscle cells; the activation of α7nAChRs can suppress local and systemic inflammation; the expression of α7nAChRs represents the acute or chronic inflammatory state to a certain extent; M1AChRs are mainly expressed in the advanced centers of the brain and regulate systemic inflammation; neuroinflammation of the MVZ, hypothalamus, and forebrain induced by sepsis not only leads to their dysfunctions but also underlies the regulatory dysfunction on systemic inflammation and immunity. Correcting the neuroinflammation of these regulatory centers and adjusting the function of α7nAChRs and M1AChRs may be two key strategies for the treatment of sepsis in the future.

Pharmacological Influencing of The Cholinergic Anti-inflammatory Pathway in Infectious Diseases and Inflammatory Pathologies

The cholinergic anti-inflammatory pathway is a part of the parasympathetic nervous system and it can also be entitled as an anti-inflammatory reflex. It consists of terminations of the vagal nerve into blood, acetylcholine released from the terminations, macrophages and other cells having α7 nicotinic acetylcholine receptor (α7 nAChR), calcium ions crossing through the receptor and interacting with nuclear factors, and erythrocytes with acetylcholinesterase (AChE) terminating the neurotransmission. Stopping of inflammatory cytokines production is the major task for the cholinergic antiinflammatory pathway. The cholinergic anti-inflammatory pathway can be stimulated or suppressed by agonizing or antagonizing α7 nAChR or by inhibition of AChE. This review is focused on cholinergic anti-inflammatory pathway regulation by drugs. Compounds that inhibit cholinesterases (for instance, huperzine, rivastigmine, galantamine), and their impact on the cholinergic anti-inflammatory pathway are discussed here and a survey of actual literature is provided.

Neural Regulation of Interactions Between Group 2 Innate Lymphoid Cells and Pulmonary Immune Cells

Emerging evidence supports the involvement of nervous system in the regulation of immune responses. Group 2 innate lymphoid cells (ILC2), which function as a crucial bridge between innate and adaptive immunity, are present in large numbers in barrier tissues. Neuropeptides and neurotransmitters have been found to participate in the regulation of ILC2, adding a new dimension to neuroimmunity. However, a comprehensive and detailed overview of the mechanisms of neural regulation of ILC2, associated with previous findings and prospects for future research, is still lacking. In this review, we compile existing information that supports neurons as yet poorly understood regulators of ILC2 in the field of lung innate and adaptive immunity, focusing on neural regulation of the interaction between ILC2 and pulmonary immune cells.

Cholinergic Modulation of Glial Function During Aging and Chronic Neuroinflammation

Aging is a complex biological process that increases the risk of age-related cognitive degenerative diseases such as dementia, including Alzheimer’s disease (AD), Lewy Body Dementia (LBD), and mild cognitive impairment (MCI). Even non-pathological aging of the brain can involve chronic oxidative and inflammatory stress, which disrupts the communication and balance between the brain and the immune system. There has been an increasingly strong connection found between chronic neuroinflammation and impaired memory, especially in AD. While microglia and astrocytes, the resident immune cells of the central nervous system (CNS), exerting beneficial effects during the acute inflammatory phase, during chronic neuroinflammation they can become more detrimental. Central cholinergic circuits are involved in maintaining normal cognitive function and regulating signaling within the entire cerebral cortex. While neuronal-glial cholinergic signaling is anti-inflammatory and anti-oxidative, central cholinergic neuronal degeneration is implicated in impaired learning, memory sleep regulation, and attention. Although there is evidence of cholinergic involvement in memory, fewer studies have linked the cholinergic anti-inflammatory and anti-oxidant pathways to memory processes during development, normal aging, and disease states. This review will summarize the current knowledge of cholinergic effects on microglia and astroglia, and their role in both anti-inflammatory and anti-oxidant mechanisms, concerning normal aging and chronic neuroinflammation. We provided details on how stimulation of α7 nicotinic acetylcholine (α7nACh) receptors can be neuroprotective by increasing amyloid-β phagocytosis, decreasing inflammation and reducing oxidative stress by promoting the nuclear factor erythroid 2-related factor 2 (Nrf2) pathways and decreasing the release of pro-inflammatory cytokines. There is also evidence for astroglial α7nACh receptor stimulation mediating anti-inflammatory and antioxidant effects by inhibiting the nuclear factor-κB (NF-κB) pathway and activating the Nrf2 pathway respectively. We conclude that targeting cholinergic glial interactions between neurons and glial cells via α7nACh receptors could regulate neuroinflammation and oxidative stress, relevant to the treatment of several neurodegenerative diseases.

Sepsis-Associated Encephalopathy: From Delirium to Dementia?

Sepsis is a major cause of death in intensive care units worldwide. The acute phase of sepsis is often accompanied by sepsis-associated encephalopathy, which is highly associated with increased mortality. Moreover, in the chronic phase, more than 50% of surviving patients suffer from severe and long-term cognitive deficits compromising their daily quality of life and placing an immense burden on primary caregivers. Due to a growing number of sepsis survivors, these long-lasting deficits are increasingly relevant. Despite the high incidence and clinical relevance, the pathomechanisms of acute and chronic stages in sepsis-associated encephalopathy are only incompletely understood, and no specific therapeutic options are yet available. Here, we review the emergence of sepsis-associated encephalopathy from initial clinical presentation to long-term cognitive impairment in sepsis survivors and summarize pathomechanisms potentially contributing to the development of sepsis-associated encephalopathy.

Vagus Nerve Stimulation Alleviates Hepatic Ischemia and Reperfusion Injury by Regulating Glutathione Production and Transformation

Inflammation and oxidative stress are pivotal mechanisms for the pathogenesis of ischemia and reperfusion injury (IRI). Vagus nerve stimulation (VNS) may participate in maintaining oxidative homeostasis and response to external stimulus or injury. We investigated whether the in vivo VNS can protect the liver from IRI. In this study, hepatic IRI were induced by ligating the vessels supplying the left and middle lobes of the liver, which underwent 1 h occlusion followed with 24 h reperfusion. VNS was initiated 15 min after ischemia and continued 30 min. Hepatic function, histology, and apoptosis rates were evaluated after 24 h reperfusion. Compared with the IRI group, VNS significantly improved hepatic function. The protective effect was accompanied by a reduction in histological damage in the ischemic area, and the apoptosis rate of hepatocytes has considerable reduction. To find the underlying mechanism, proteomic analysis was performed and differential expression of glutathione synthetase (GSS) and glutathione S-transferase (GST) was observed. Subsequently, test results indicated that VNS upregulated the expression of mRNA and protein of GSS and GST. Meanwhile, VNS increased the plasma levels of glutathione and glutathione peroxidases. We found that VNS alleviated hepatic IRI by upregulating the antioxidant glutathione via the GSS/glutathione/GST signaling pathway.

Sepsis-associated encephalopathy: a vicious cycle of immunosuppression

Sepsis-associated encephalopathy (SAE) is commonly complicated by septic conditions, and is responsible for increased mortality and poor outcomes in septic patients. Uncontrolled neuroinflammation and ischemic injury are major contributors to brain dysfunction, which arises from intractable immune malfunction and the collapse of neuroendocrine immune networks, such as the cholinergic anti-inflammatory pathway, hypothalamic-pituitary-adrenal axis, and sympathetic nervous system. Dysfunction in these neuromodulatory mechanisms compromised by SAE jeopardizes systemic immune responses, including those of neutrophils, macrophages/monocytes, dendritic cells, and T lymphocytes, which ultimately results in a vicious cycle between brain injury and a progressively aberrant immune response. Deep insight into the crosstalk between SAE and peripheral immunity is of great importance in extending the knowledge of the pathogenesis and development of sepsis-induced immunosuppression, as well as in exploring its effective remedies.

Gut Inflammation in Association With Pathogenesis of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disease that is generally thought to be caused by multiple factors, including environmental and genetic factors. Emerging evidence suggests that intestinal disturbances, such as constipation, are common non-motor symptoms of PD. Gut inflammation may be closely associated with pathogenesis in PD. This review aims to discuss the cross-talk between gut inflammation and PD pathology initiation and progression. Firstly, we will highlight the studies demonstrating how gut inflammation is related to PD. Secondly, we will analyze how gut inflammation spreads from the gastro-intestine to the brain. Here, we will mainly discuss the neural pathway of pathologic α-syn and the systemic inflammatory routes. Thereafter, we will address how alterations in the brain subsequently lead to dopaminergic neuron degeneration, in which oxidative stress, glutamate excitotoxicity, T cell driven inflammation and cyclooxygenase-2 (COX-2) are involved. We conclude a model of PD triggered by gut inflammation, which provides a new angle to understand the mechanisms of the disease.

Spectral analysis of heart rate variability for trauma outcome prediction: an analysis of 210 ICU multiple trauma patients

PURPOSE

This study aimed to test and compare short-term spectral HRV indices with most used trauma scorings in outcome prediction of multiple trauma, and then to explore the efficacy of their combined application.

METHODS

A prospective study was conducted for patients with blunt multiple trauma admitted to an emergency intensive care unit (ICU) between January 2016 and December 2017. Short-term spectral HRV indices on admission were measured, including normalized low-frequency power (nLF), normalized high-frequency power (nHF), and the nLF/nHF ratio. Injury severity score (ISS), new injury severity score (NISS), and revised trauma score (RTS) were evaluated for each patient, as well as probability of survival (Ps) by trauma and injury severity score (TRISS) model. The primary outcome was 30-day mortality and secondary outcomes were incidence of multiple organ dysfunction syndrome (MODS) and length of ICU stay.

RESULTS

Two hundred and ten patients were recruited. The nLF/nHF ratio, RTS, and Ps_(TRISS) were independent predictors of 30-day mortality, while nLF/nHF, NISS and RTS were independent predictors of MODS. The area under the receiver operating characteristic (ROC) curve (AUC) of nLF/nHF for 30-day mortality prediction was 0.924, comparable to RTS (0.951) and Ps_(TRISS) (0.892). AUC of nLF/nHF-RTS combination was 0.979, significantly greater than that of each alone. Combination of nLF/nHF and Ps_(TRISS) showed an increased AUC (0.984) compared to each of them. The nLF/nHF ratio presented a similar AUC (0.826) to NISS (0.818) or RTS (0.850) for MODS prediction. AUC of nLF/nHF-RTS combination was 0.884, significantly greater than that of nLF/nHF. Combination of nLF/nHF and NISS showed a greater AUC (0.868) than each alone. The nLF/nHF ratio, NISS, RTS, and Ps_(TRISS) were correlated with length of ICU stay for survivors, with correlation coefficients 0.476, 0.617, - 0.588, and - 0.539.

CONCLUSIONS

These findings suggest that the short-term spectral analysis of HRV might be a potential early tool to assess injury severity and predict outcome of multiple trauma. Combination of nLF/nHF and conventional trauma scores can provide more accuracy in outcome prediction of multiple trauma.

Inhibition of Cerebral High-Mobility Group Box 1 Protein Attenuates Multiple Organ Damage and Improves T Cell-Mediated Immunity in Septic Rats

Sepsis remains one of the leading causes of mortality in intensive care units, but there is a shortage of effective treatments. A dysregulated host immune response and multiple organ injury are major factors for the pathogenesis and progression of sepsis, which require specific mechanism and treatment. In the present study, we performed an intracerebroventricular (ICV) injection of BoxA, a specific antagonist of high-mobility group box 1 protein (HMGB1), in septic rats that were produced by cecal ligation and puncture surgery; we further assessed the functional changes of multiple organs and splenic T lymphocytes. We found that the inhibition of cerebral HMGB1 significantly alleviated multiple organ damage under septic exposure, including damage to the heart, liver, lungs, and kidneys; reversed the immune dysfunction of T cells; and increased the survival of septic rats. These data suggest that central HMGB1 might be a potential therapeutic target for septic challenge and that inhibition of brain HMGB1 can protect against multiple organ dysfunction induced by sepsis.

Septic Encephalopathy

PURPOSE OF THE REVIEW

To discuss the diagnostic approach to patients with septic encephalopathy as well as the need for specific neuro-monitoring and the perspectives on future therapeutic approaches in this setting.

RECENT FINDINGS

Most of data-concern experimental studies evaluating the pathophysiology of septic encephalopathy. A combination of neurodegenerative pathways with neurovascular injury is the cornerstone for the development of such complication and the long-term neurological sequelae among survivors. Septic encephalopathy is a common complication in septic patients. Clinical presentation may range from mild confusion and disorientation to convulsions and deep coma. The diagnosis of septic encephalopathy is made difficult by the lack of any specific clinical and non-clinical feature, in particular among sedated patients in whom neurological examination is unreliable. In spite of the high mortality rate associated with this condition, there is no prophylactic or targeted therapy to reduce or minimize brain damage in septic patients and clinical management is limited to the treatment of the underlying infection.

Long-Term Cognitive Outcomes After Sepsis: a Translational Systematic Review

Sepsis is systemic inflammatory response syndrome with a life-threatening organ dysfunction that is caused by an unbalanced host immune response in an attempt to eliminate invasive microorganisms. We posed questions, "Does sepsis survivor patients have increased risk of neuropsychiatric manifestations?" and "What is the mechanism by which sepsis induces long-term neurological sequelae, particularly substantial cognitive function decline in survivor patients and in pre-clinical sepsis models?" The studies were identified by searching PubMed/MEDLINE (National Library of Medicine), PsycINFO, EMBASE (Ovid), LILACS (Latin American and Caribbean Health Sciences Literature), IBECS (Bibliographical Index in Spanish in Health Sciences), and Web of Science databases for peer-reviewed journals that were published until January 2018. A total of 3555 papers were included in the primary screening. After that, 130 articles were selected for the study. A number of pre-clinical studies have shown an auto amplification of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6 in the first few hours after sepsis induction, also increased blood-brain barrier permeability, elevated levels of matrix metalloproteinases, increased levels of damage-associated molecular patterns were demonstrated. In addition, the rodents presented long-term cognitive impairment in different behavioral tasks that were prevented by blocking the mechanism of action of these inflammatory mediators. Clinical studies have showed that sepsis survivors presented increased bodily symptoms such as fatigue, pain, visual disturbances, gastrointestinal problems, and neuropsychiatric problems compared to before sepsis. Sepsis leaves the survivors with an aftermath of physiological, neuropsychiatric, and functional impairment. Systematic review registration: CRD42017071755.