Cholinergic leukocytes in sepsis and at the neuroimmune junction in the spleen

Complementary and alternative medicine on cognitive defects and neuroinflammation after sepsis

Sepsis-associated encephalopathy (SAE) is a common manifestation of sepsis, ranging from mild confusion and delirium to severe cognitive impairment and deep coma. SAE is associated with higher mortality and long-term outcomes, particularly substantial declines in cognitive function. The mechanisms of SAE probably include neuroinflammation that is mediated by systemic inflammation and ischemic lesions in the brain, a disrupted blood-brain barrier, oxidative stress, neurotransmitter dysfunction, and severe microglial activation. Increasing evidence suggests that complementary and alternative medicine, especially Traditional Chinese Medicine (TCM), is favorable in alleviating cognitive decline after sepsis. Here, we summarized the studies of traditional herbal remedies, TCM formulas and acupuncture therapy in animal models of neurological dysfunctions after sepsis in recent decades and reviewed their potential mechanisms.

Immune Cells in the Spleen of Mice Mediate the Inflammatory Response Induced by Mannheimia haemolytica A2 Serotype

(1) Background: Mannheimia haemolytica (M. haemolytica) is an opportunistic pathogen and is mainly associated with respiratory diseases in cattle, sheep, and goats. (2) Methods: In this study, a mouse infection model was established using a M. haemolytica strain isolated from goats. Histopathological observations were conducted on various organs of the mice, and bacterial load determination and RNA-seq analysis were specifically performed on the spleens of the mice. (3) Results: The findings of this study suggest that chemokines, potentially present in the spleen of mice following a M. haemolytica challenge, may induce the migration of leukocytes to the spleen and suppress the release of pro-inflammatory factors through a negative feedback regulation mechanism. Additionally, an interesting observation was made regarding the potential of hematopoietic stem/progenitor cells congregating in the spleen to differentiate into immune cells, which could potentially collaborate with leukocytes in their efforts to counteract M. haemolytica invasion. (4) Conclusions: This study revealed the immune regulation mechanism induced by M. haemolytica in the mouse spleen, providing valuable insights into host-pathogen interactions and offering a theoretical basis for the prevention, control, and treatment of mannheimiosis.

GTS-21 Enhances Regulatory T Cell Development from T Cell Receptor-Activated Human CD4+ T Cells Exhibiting Varied Levels of CHRNA7 and CHRFAM7A Expression

Immune cells such as T cells and macrophages express α7 nicotinic acetylcholine receptors (α7 nAChRs), which contribute to the regulation of immune and inflammatory responses. Earlier findings suggest α7 nAChR activation promotes the development of regulatory T cells (Tregs) in mice. Using human CD4+ T cells, we investigated the mRNA expression of the α7 subunit and the human-specific dupα7 nAChR subunit, which functions as a dominant-negative regulator of ion channel function, under resting conditions and T cell receptor (TCR)-activation. We then explored the effects of the selective α7 nAChR agonist GTS-21 on proliferation of TCR-activated T cells and Treg development. Varied levels of mRNA for both the α7 and dupα7 nAChR subunits were detected in resting human CD4+ T cells. mRNA expression of the α7 nAChR subunit was profoundly suppressed on days 4 and 7 of TCR-activation as compared to day 1, whereas mRNA expression of the dupα7 nAChR subunit remained nearly constant. GTS-21 did not alter CD4+ T cell proliferation but significantly promoted Treg development. These results suggest the potential ex vivo utility of GTS-21 for preparing Tregs for adoptive immunotherapy, even with high expression of the dupα7 subunit.

In a secondary analysis from a randomised, double-blind placebo-controlled trial Dexmedetomidine blocks cholinergic dysregulation in delirium pathogenesis in patients with major surgery

Dexmedetomidine is an alpha-2 adrenoreceptor agonist with anti-inflammatory and anti-delirogenic properties. Pathogenesis of postoperative delirium (POD) includes cholinergic dysfunction and deregulated inflammatory response to surgical trauma. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are discussed as biomarkers for both POD and severity in acute inflammation. To show whether there is a link between blood cholinesterase activities and dexmedetomidine, we performed a secondary analysis of a randomised, double-blind, placebo-controlled trial that recently showed a lower incidence of POD in the dexmedetomidine group. Abdominal or cardiac surgical patients aged ≥ 60 years were randomised to receive dexmedetomidine or placebo intra- and postoperatively in addition to standard general anaesthesia. We analysed the course of perioperative cholinesterase activities of 56 patients, measured preoperatively and twice postoperatively. Dexmedetomidine resulted in no change in AChE activity and caused a rapid recovery of BChE activity after an initial decrease, while placebo showed a significant decrease in both cholinesterase activities. There were no significant between-group differences at any point in time. From these data it can be assumed that dexmedetomidine could alleviate POD via altering the cholinergic anti-inflammatory pathway (CAIP). We advocate for further investigations to show the direct connection between dexmedetomidine and cholinesterase activity.

Toll-like receptor 2 deficiency relieves splenic immunosuppression during sepsis

Immunosuppression is associated with long-term mortality during sepsis. However, the underlying mechanism of immunosuppression remains poorly understood. Toll-like receptor 2 (TLR2) contributes to sepsis pathogenesis. We sought to determine the role of TLR2 in immunosuppression in the spleen during polymicrobial sepsis. Using an experimental model of polymicrobial sepsis induced by cecal ligation and puncture (CLP), we measured the expression of inflammatory cytokines and chemokines in spleen 6 and 24 h after CLP to evaluate the immune response, and compared the expression of inflammatory cytokines and chemokines, apoptosis, and intracellular ATP production in spleen of wild-type (WT) and TLR2-deficient (TLR2^-/-) mice 24 h after CLP. We found that pro-inflammatory cytokines and chemokines, such as TNF-α and IL-1β peaked 6 h after CLP, while IL-10, an anti-inflammatory cytokine, peaked 24 h after CLP in the spleen. At this later time point, TLR2^-/- mice presented decreased levels of IL-10 and decreased caspase 3 activation but no significant difference in intracellular ATP production in spleen compared to WT mice. Our data imply that TLR2 has a pronounced effect on sepsis-induced immunosuppression in spleen.

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.

Dexmedetomidine Restores Autophagic Flux, Modulates Associated microRNAs and the Cholinergic Anti-inflammatory Pathway upon LPS-Treatment in Rats

Infections and perioperative stress can lead to neuroinflammation, which in turn is linked to cognitive impairments such as postoperative delirium or postoperative cognitive dysfunctions. The α2-adrenoceptor agonist dexmedetomidine (DEX) prevents cognitive impairments and has organo-protective and anti-inflammatory properties. Macroautophagy (autophagy) regulates many biological processes, but its role in DEX-mediated anti-inflammation and the underlying mechanism of DEX remains largely unclear. We were interested how a pretreatment with DEX protects against lipopolysaccharide (LPS)-induced inflammation in adult male Wistar rats. We used Western blot and activity assays to study how DEX modulated autophagy- and apoptosis-associated proteins as well as molecules of the cholinergic anti-inflammatory pathway, and qPCR to analyse the expression of autophagy and inflammation-associated microRNAs (miRNA) in the spleen, cortex and hippocampus at different time points (6 h, 24 h, 7 d). We showed that a DEX pretreatment prevents LPS-induced impairments in autophagic flux and attenuates the LPS-induced increase in the apoptosis-associated protein cleaved poly(ADP-ribose)-polymerase (PARP) in the spleen. Both, DEX and LPS altered miRNA expression and molecules of the cholinergic anti-inflammatory pathway in the spleen and brain. While only a certain set of miRNAs was up- and/or downregulated by LPS in each tissue, which was prevented or attenuated by a DEX pretreatment in the spleen and hippocampus, all miRNAs were up- and/or downregulated by DEX itself - independent of whether or not they were altered by LPS. Our results indicate that the organo-protective effect of DEX may be mediated by autophagy, possibly by acting on associated miRNAs, and the cholinergic anti-inflammatory pathway. Preventive effects of DEX on LPS-induced inflammation. DEX restores the LPS-induced impairments in autophagic flux, attenuates PARP cleavage and alters molecules of the cholinergic system in the spleen. Furthermore, DEX alters and prevents LPS-induced miRNA expression changes in the spleen and brain along with LPS.

Age-Related Variation in Sympathetic Nerve Distribution in the Human Spleen

Introduction: The cholinergic anti-inflammatory pathway (CAIP) has been proposed as an efferent neural pathway dampening the systemic inflammatory response via the spleen. The CAIP activates the splenic neural plexus and a subsequent series of intrasplenic events, which at least require a close association between sympathetic nerves and T cells. Knowledge on this pathway has mostly been derived from rodent studies and only scarce information is available on the innervation of the human spleen. This study aimed to investigate the sympathetic innervation of different structures of the human spleen, the topographical association of nerves with T cells and age-related variations in nerve distribution.

Materials and Methods: Spleen samples were retrieved from a diagnostic archive and were allocated to three age groups; neonates, 10–25 and 25–70 years of age. Sympathetic nerves and T cells were identified by immunohistochemistry for tyrosine hydroxylase (TH) and the membrane marker CD3, respectively. The overall presence of sympathetic nerves and T cells was semi-automatically quantified and expressed as total area percentage. A predefined scoring system was used to analyze the distribution of nerves within different splenic structures.

Results: Sympathetic nerves were observed in all spleens and their number appeared to slightly increase from birth to adulthood and to decrease afterward. Irrespective to age, more than halve of the periarteriolar lymphatic sheaths (PALSs) contained sympathetic nerves in close association with T cells. Furthermore, discrete sympathetic nerves were observed in the capsule, trabeculae and red pulp and comparable to the total amount of sympathetic nerves, showed a tendency to decrease with age. No correlation was found between the number of T cells and sympathetic nerves.

Conclusion: The presence of discrete sympathetic nerves in the splenic parenchyma, capsule and trabecular of human spleens could suggest a role in functions other than vasoregulation. In the PALS, sympathetic nerves were observed to be in proximity to T cells and is suggestive for the existence of the CAIP in humans. Since sympathetic nerve distribution shows interspecies and age-related variation, and our general understanding of the relative and spatial contribution of splenic innervation in immune regulation is incomplete, it remains difficult to estimate the anti-inflammatory potential of targeting splenic nerves in patients.

The Therapeutic Value of Hydralazine in Reducing Inflammatory Response, Oxidative Stress, and Mortality in Animal Sepsis: Involvement of the PI3K/AKT Pathway

ABSTRACT

Sepsis is an amplified systemic immune-inflammatory response produced by a microorganism, which involves activation of inflammatory cytokine signaling pathways and oxidative stress. A variety of studies have shown that hydralazine (HDZ) has potent antioxidant and anti-inflammatory proprieties. Therefore, we hypothesize that HDZ can improve the clinical outcome of sepsis. Thus, this work aimed to evaluate therapeutic value of HDZ in reducing inflammatory response, oxidative stress, and mortality in animal sepsis, and to investigate its possible mechanism of action. Sepsis was induced by the cecal ligation and puncture (CLP) method in Wistar rats. After surgery, the animals were randomly divided into three groups: sham, sepsis, and sepsis + HDZ (1 mg/kg, s.c.). All groups were monitored for 48 h to assess survival rate, and clinical, hemodynamic, biochemical, and cellular parameters. After euthanasia, blood, spleen, liver, and kidneys were collected for analysis. Blood serum cytokines, tissue myeloperoxidase (MPO) activity, and oxidative stress parameters were assessed. Involvement of the PI3K/Akt pathway was also investigated. Sepsis was successfully induced by the CLP technique. HDZ treatment increased the survival rate (from 50% to 90%), improved glycemia control, reduced the clinical severity sepsis and mean arterial pressure; and prevented increased MPO activity, TNF-α, IL-1β, IL-10 levels, and oxidative damage markers. Additionally, HDZ significantly prevented the increase of Akt activation in the liver and kidney. HDZ largely mitigated the effects of sepsis by suppressing inflammatory and antioxidant responses via the PI3K/Akt pathway. These findings provide evidence that HDZ can be a new therapeutic alternative for treating sepsis.

Regulation of Immune Functions by Non-Neuronal Acetylcholine (ACh) via Muscarinic and Nicotinic ACh Receptors

Acetylcholine (ACh) is the classical neurotransmitter in the cholinergic nervous system. However, ACh is now known to regulate various immune cell functions. In fact, T cells, B cells, and macrophages all express components of the cholinergic system, including ACh, muscarinic, and nicotinic ACh receptors (mAChRs and nAChRs), choline acetyltransferase, acetylcholinesterase, and choline transporters. In this review, we will discuss the actions of ACh in the immune system. We will first briefly describe the mechanisms by which ACh is stored in and released from immune cells. We will then address Ca²⁺ signaling pathways activated via mAChRs and nAChRs on T cells and B cells, highlighting the importance of ACh for the function of T cells, B cells, and macrophages, as well as its impact on innate and acquired (cellular and humoral) immunity. Lastly, we will discuss the effects of two peptide ligands, secreted lymphocyte antigen-6/urokinase-type plasminogen activator receptor-related peptide-1 (SLURP-1) and hippocampal cholinergic neurostimulating peptide (HCNP), on cholinergic activity in T cells. Overall, we stress the fact that ACh does not function only as a neurotransmitter; it impacts immunity by exerting diverse effects on immune cells via mAChRs and nAChRs.

Cholinergic System and Its Therapeutic Importance in Inflammation and Autoimmunity

Neurological and immunological signals constitute an extensive regulatory network in our body that maintains physiology and homeostasis. The cholinergic system plays a significant role in neuroimmune communication, transmitting information regarding the peripheral immune status to the central nervous system (CNS) and vice versa. The cholinergic system includes the neurotransmitter\ molecule, acetylcholine (ACh), cholinergic receptors (AChRs), choline acetyltransferase (ChAT) enzyme, and acetylcholinesterase (AChE) enzyme. These molecules are involved in regulating immune response and playing a crucial role in maintaining homeostasis. Most innate and adaptive immune cells respond to neuronal inputs by releasing or expressing these molecules on their surfaces. Dysregulation of this neuroimmune communication may lead to several inflammatory and autoimmune diseases. Several agonists, antagonists, and inhibitors have been developed to target the cholinergic system to control inflammation in different tissues. This review discusses how various molecules of the neuronal and non-neuronal cholinergic system (NNCS) interact with the immune cells. What are the agonists and antagonists that alter the cholinergic system, and how are these molecules modulate inflammation and immunity. Understanding the various functions of pharmacological molecules could help in designing better strategies to control inflammation and autoimmunity.

Metabolomic Analysis of the Effects of Adipose-Derived Mesenchymal Stem Cell Treatment on Rats With Sepsis-Induced Acute Lung Injury

Given the high mortality associated with sepsis, there is an urgent need for a full understanding of sepsis pathophysiology and finding new therapeutic regimens. Adipose-derived mesenchymal stem cells (ADMSCs) has been proven to have anti-inflammatory effects and could be used to treat cecal ligation and puncture (CLP) induced lung and liver injury in septic rat models. In this study, we used metabolomics to investigate small molecule metabolites between CLP and ADMSCs treatment groups. Sixty SD rats were randomly assigned to the sham operation group (SC group), the CLP group, and the CLP+ADMSCs group (CLP-ADMSCs group). We used liquid mass spectrometry-chromatography to detect metabolic changes in plasma and lung tissues. Compared with the SC group, the metabolic profile of plasma and lung tissues changed significantly 24 h after CLP. Moreover, 22 and 11 main differential metabolites involved in amino acid and glycerophospholipid metabolism were found in plasma and lung tissues, respectively. After the rats were injected with ADMSCs, these differential metabolites were reverse-regulated both in plasma and lung tissues. Besides, ADMSCs improved the survival rate and down-regulated the concentration of TNF-α and IL-6 at 24 h after CLP. The correlational analysis between plasma of IL-6/TNF-α and metabolites suggested that acetylcholine, spermine, phenylalanine, threonine of plasma and phosphatidylcholine (36:4) of lung tissues were significantly associated with IL-6/TNF-α in CLP and CLP-ADMSCs groups. ADMSCs might reverse abnormal metabolic pathways by reducing anti-inflammatory factors in sepsis-induced ALI. Our findings may provide novel metabolic mechanism of ADMSCs therapy for sepsis.