Calcium sensing receptor contribute to early brain injury through the CaMKII/NLRP3 pathway after subarachnoid hemorrhage in mice

The pivotal role of microglia in injury and the prognosis of subarachnoid hemorrhage

Subarachnoid hemorrhage leads to a series of pathological changes, including vascular spasm, cellular apoptosis, blood-brain barrier damage, cerebral edema, and white matter injury. Microglia, which are the key immune cells in the central nervous system, maintain homeostasis in the neural environment, support neurons, mediate apoptosis, participate in immune regulation, and have neuroprotective effects. Increasing evidence has shown that microglia play a pivotal role in the pathogenesis of subarachnoid hemorrhage and affect the process of injury and the prognosis of subarachnoid hemorrhage. Moreover, microglia play certain neuroprotective roles in the recovery phase of subarachnoid hemorrhage. Several approaches aimed at modulating microglia function are believed to attenuate subarachnoid hemorrhage injury. This provides new targets and ideas for the treatment of subarachnoid hemorrhage. However, an in-depth and comprehensive summary of the role of microglia after subarachnoid hemorrhage is still lacking. This review describes the activation of microglia after subarachnoid hemorrhage and their roles in the pathological processes of vasospasm, neuroinflammation, neuronal apoptosis, blood-brain barrier disruption, cerebral edema, and cerebral white matter lesions. It also discusses the neuroprotective roles of microglia during recovery from subarachnoid hemorrhage and therapeutic advances aimed at modulating microglial function after subarachnoid hemorrhage. Currently, microglia in subarachnoid hemorrhage are targeted with TLR inhibitors, nuclear factor-κB and STAT3 pathway inhibitors, glycine/tyrosine kinases, NLRP3 signaling pathway inhibitors, Gasdermin D inhibitors, vincristine receptor α receptor agonists, ferroptosis inhibitors, genetic modification techniques, stem cell therapies, and traditional Chinese medicine. However, most of these are still being evaluated at the laboratory stage. More clinical studies and data on subarachnoid hemorrhage are required to improve the treatment of subarachnoid hemorrhage.

PARP-1 dependent cell death pathway (Parthanatos) mediates early brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a neurological condition with high mortality and poor prognosis, and there are currently no effective therapeutic drugs available. Poly (ADP-ribose) polymerase 1 (PARP-1) dependent cell death pathway-parthanatos is closely associated with stroke. We investigated improvements in neurological function, oxidative stress, blood-brain barrier and parthanatos-related protein expression in rats with SAH after intraperitoneal administration of PARP-1 inhibitor (AG14361). Our study found that the expression of parthanatos-related proteins was significantly increased after SAH. Immunofluorescence staining showed increased expression of apoptosis-inducing factor (AIF) in the nucleus after SAH. Administration of PARP-1 inhibitor significantly reduced malondialdehyde (MDA) level and the expression of parthanatos-related proteins. Immunofluorescence staining showed that PARP-1 inhibitor reduced the expression of 8-hydroxy-2' -deoxyguanosine (8-OHdG) and thus reduced oxidative stress. Moreover, PARP-1 inhibitor could inhibit inflammation-associated proteins level and neuronal apoptosis, protect the blood-brain barrier and significantly improve neurological function after SAH. These results suggest that PARP-1 inhibitor can significantly improve SAH, and the underlying mechanism may be through inhibiting parthanatos pathway.

NPS-2143 inhibit glioma progression by suppressing autophagy through mediating AKT-mTOR pathway

Gliomas are the most common tumours in the central nervous system. In the present study, we aimed to find a promising anti-glioma compound and investigate the underlying molecular mechanism. Glioma cells were subjected to the 50 candidate compounds at a final concentration of 10 μM for 72 h, and CCK-8 was used to evaluate their cytotoxicity. NPS-2143, an antagonist of calcium-sensing receptor (CASR), was selected for further study due to its potent cytotoxicity to glioma cells. Our results showed that NPS-2143 could inhibit the proliferation of glioma cells and induce G1 phase cell cycle arrest. Meanwhile, NPS-2143 could induce glioma cell apoptosis by increasing the caspase-3/6/9 activity. NPS-2143 impaired the immigration and invasion ability of glioma cells by regulating the epithelial-mesenchymal transition process. Mechanically, NPS-2143 could inhibit autophagy by mediating the AKT-mTOR pathway. Bioinformatic analysis showed that the prognosis of glioma patients with low expression of CASR mRNA was better than those with high expression of CASR mRNA. Gene set enrichment analysis showed that CASR was associated with cell adhesion molecules and lysosomes in glioma. The nude mice xenograft model showed NPS-2143 could suppress glioma growth in vivo. In conclusion, NPS-2143 can suppress the glioma progression by inhibiting autophagy.

Quercetin alleviates zearalenone-induced apoptosis and necroptosis of porcine renal epithelial cells by inhibiting CaSR/CaMKII signaling pathway

Zearalenone (ZEA) is a mycotoxin that is highly contaminated in feed and can cause severe toxic effects on the kidneys and other organs of animals. Quercetin (QUE) is a plant-derived flavonoid with a variety of detoxification properties, but the mechanism by which QUE detoxifies the toxic effects induced by ZEA has not yet been fully elucidated. We treated porcine kidney cells (PK15) with 80 μM ZEA and/or 30 μM QUE. The results showed that ROS and MDA levels were increased, antioxidant system levels were down-regulated, anti-apoptotic factor expression levels were decreased, and apoptotic and necroptosis-related factors were up-regulated after ZAE exposure. In addition, the results of Ca2+ staining, mitochondrial membrane potential, and mitochondrial dynamics-related indicators showed that ZEA induced Ca2+ overload in PK15 cells and increased mitochondrial Ca2+ uptake (MCU expression increased). The accumulated ROS and free Ca2+ further aggravate mitochondrial damage and eventually lead to mitochondrial pathway apoptosis and necroptosis. Nevertheless, QUE targets CaSR to inhibit the CaSR/CaMKII pathway and regulate calcium homeostasis, thereby alleviating apoptosis and necroptosis mediated by mitochondrial dynamic disorder and dysfunction. The present study demonstrated the mechanism by which ZEA induces apoptosis and necroptosis in PK15 and the protective role of QUE in this process.

Connection between oxidative stress and subcellular organelle in subarachnoid hemorrhage: Novel mechanisms and therapeutic implications

Spontaneous subarachnoid hemorrhage (SAH) is one of the most devastating forms of stroke, with limited treatment modalities and poor patient outcomes. Previous studies have proposed multiple prognostic factors; however, relative research on treatment has not yet yielded favorable clinical outcomes. Moreover, recent studies have suggested that early brain injury (EBI) occurring within 72 h after SAH may contribute to its poor clinical outcomes. Oxidative stress is recognized as one of the main mechanisms of EBI, which causes damage to various subcellular organelles, including the mitochondria, nucleus, endoplasmic reticulum (ER), and lysosomes. This could lead to significant impairment of numerous cellular functions, such as energy supply, protein synthesis, and autophagy, which may directly contribute to the development of EBI and poor long-term prognostic outcomes. In this review, the mechanisms underlying the connection between oxidative stress and subcellular organelles after SAH are discussed, and promising therapeutic options based on these mechanisms are summarized.

Early Brain Injury After Subarachnoid Hemorrhage: Incidence and Mechanisms

Aneurysmal subarachnoid hemorrhage is a devastating condition causing significant morbidity and mortality. While outcomes from subarachnoid hemorrhage have improved in recent years, there continues to be significant interest in identifying therapeutic targets for this disease. In particular, there has been a shift in emphasis toward secondary brain injury that develops in the first 72 hours after subarachnoid hemorrhage. This time period of interest is referred to as the early brain injury period and comprises processes including microcirculatory dysfunction, blood-brain-barrier breakdown, neuroinflammation, cerebral edema, oxidative cascades, and neuronal death. Advances in our understanding of the mechanisms defining the early brain injury period have been accompanied by improved imaging and nonimaging biomarkers for identifying early brain injury, leading to the recognition of an elevated clinical incidence of early brain injury compared with prior estimates. With the frequency, impact, and mechanisms of early brain injury better defined, there is a need to review the literature in this area to guide preclinical and clinical study.

Inhibition of Calcium-Sensing Receptor Alleviates Chronic Intermittent Hypoxia-Induced Cognitive Dysfunction via CaSR-PKC-ERK1/2 Pathway

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is typically characterized by chronic intermittent hypoxia (CIH), associated with cognitive dysfunction in children. Calcium-sensing receptor (CaSR) mediates the apoptosis of hippocampal neurons in various diseases. However, the effect of CaSR on OSAHS remains elusive. In the present study, we investigated the role of CaSR in CIH-induced memory dysfunction and underlying mechanisms on regulation of PKC-ERK1/2 signaling pathway in vivo and in vitro. CIH exposures for 4 weeks in mice, modeling OSAHS, contributed to cognitive dysfunction. CIH accelerated apoptosis of hippocampal neurons and resulted in the synaptic plasticity deficit via downregulated synaptophysin (Syn) protein level. The mice were intraperitoneally injected with CaSR inhibitor (NPS2143) 30 min before CIH exposure and the results demonstrated CaSR inhibitor alleviated the apoptosis and synaptic plasticity deficit in the hippocampus of CIH mice. We established intermittent hypoxia PC12 cell model and found that the activation of CaSR accelerated CIH-induced PC12 apoptosis and synaptic plasticity deficit by upregulated p-ERK1/2 and PKC. Overall, our findings revealed that CaSR held a critical function on CIH-induced cognitive dysfunction in mice by accelerating hippocampal neuronal apoptosis and reducing synaptic plasticity via augmenting CaSR-PKC-ERK1/2 pathway; otherwise, inhibition of CaSR alleviated CIH-induced cognitive dysfunction.

NLRP3 Inflammasome’s Activation in Acute and Chronic Brain Diseases—An Update on Pathogenetic Mechanisms and Therapeutic Perspectives with Respect to Other Inflammasomes

Increasingly prevalent acute and chronic human brain diseases are scourges for the elderly. Besides the lack of therapies, these ailments share a neuroinflammation that is triggered/sustained by different innate immunity-related protein oligomers called inflammasomes. Relevant neuroinflammation players such as microglia/monocytes typically exhibit a strong NLRP3 inflammasome activation. Hence the idea that NLRP3 suppression might solve neurodegenerative ailments. Here we review the recent Literature about this topic. First, we update conditions and mechanisms, including RNAs, extracellular vesicles/exosomes, endogenous compounds, and ethnic/pharmacological agents/extracts regulating NLRP3 function. Second, we pinpoint NLRP3-activating mechanisms and known NLRP3 inhibition effects in acute (ischemia, stroke, hemorrhage), chronic (Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, MS, ALS), and virus-induced (Zika, SARS-CoV-2, and others) human brain diseases. The available data show that (i) disease-specific divergent mechanisms activate the (mainly animal) brains NLRP3; (ii) no evidence proves that NLRP3 inhibition modifies human brain diseases (yet ad hoc trials are ongoing); and (iii) no findings exclude that concurrently activated other-than-NLRP3 inflammasomes might functionally replace the inhibited NLRP3. Finally, we highlight that among the causes of the persistent lack of therapies are the species difference problem in disease models and a preference for symptomatic over etiologic therapeutic approaches. Therefore, we posit that human neural cell-based disease models could drive etiological, pathogenetic, and therapeutic advances, including NLRP3’s and other inflammasomes’ regulation, while minimizing failure risks in candidate drug trials.

Calcium-sensing receptor-mediated NLRP3 inflammasome activation in rheumatoid arthritis and autoinflammation

The calcium-sensing receptor (CaSR) is expressed in many cell types - including immune cells and in particular circulating monocytes. Here, the receptor plays an important physiological role as a regulator of constitutive macropinocytosis. This review article provides an overview of the literature on the role of the calcium sensing receptor in the context of inflammatory processes. Special emphasis is laid upon the importance for monocytes in the context of rheumatoid arthritis. We have shown previously, that stimulation of the receptor by increased extracellular Ca²⁺ ([Ca²⁺]_ex) triggers a pro-inflammatory response due to NLRP3 inflammasome assembly and interleukin (IL)-1β release. The underlying mechanism includes macropinocytosis of calciprotein particles (CPPs), which are taken up in a [Ca²⁺]_ex-induced, CaSR dependent manner, and leads to strong IL-1β release. In rheumatoid arthritis (RA), this uptake and the resulting IL-1β release is significantly increased due to increased expression of the receptor. Moreover, increased [Ca²⁺]_ex-induced CPP uptake and IL-1β release is associated with more active disease, while CaSR overexpression has been reported to be associated with cardiovascular complications of RA. Most importantly, however, in animal experiments with arthritic mice, increased local calcium concentrations are present, which in combination with release of fetuin-A from eroded bone could contribute to formation of CPPs. We propose, that increased [Ca²⁺]_ex, CPPs and pro-inflammatory cytokines drive a vicious cycle of inflammation and bone destruction which in turn offers new potential therapeutic approaches.

Inflammatory role of microglia in brain injury caused by subarachnoid hemorrhage

Early brain injury is a series of pathophysiological changes and direct damage of brain tissue within 72 h after subarachnoid hemorrhage before cerebral vasospasm occurs. Early brain injury is a key factor affecting the prognosis of subarachnoid hemorrhage, and its possible pathological mechanisms include oxidative stress, cell apoptosis, autophagy, and immune inflammation. Microglia are important immune cells of the central nervous system. Microglia play a dual role in protection and injury. Microglia are involved in the occurrence of brain edema, the processes of neuronal apoptosis, and the blood-brain barrier disruption after subarachnoid hemorrhage (SAH) through the signaling pathways mediated by receptors such as Toll-like receptor 4 (TLR4), calcium-sensing receptor (CaSR), and triggering receptor expressed on myeloid cells-1 (TREM-1), which secrete pro-inflammatory cytokines such as interleukins and tumor necrosis factor α. Conversely, they exert their anti-inflammatory and protective effects by expressing substances such as neuroglobin and heme oxygenase-1. This article reviews the latest developments in single-cell transcriptomics for microglia in early brain injury after subarachnoid hemorrhage and its inflammatory role.

The role of calcium-sensitive receptor in ovalbumin-induced airway inflammation and hyperresponsiveness in juvenile mice with asthma

The role of the calcium-sensitive receptor (CaSR) was assessed in a juvenile mouse model of asthma induced by ovalbumin (OVA). The experiment was divided into normal control, OVA, and OVA +2.5/5 mg/kg NPS2143 (a CaSR antagonist) groups. OVA induction was performed in all groups except the normal control, followed by assessing airway hyperresponsiveness (AHR) and lung pathological changes. Serum OVA-specific IgE and IgG1 were detected with an enzyme-linked immunosorbent assay (ELISA), and inflammatory cells were counted in bronchoalveolar lavage fluid (BALF). Real-time quantitative polymerase chain reaction, ELISA, and western blotting were performed to detect gene and protein expression. NPS2143 improved the OVA-induced AHR in mice, and AHR was higher in the OVA +2.5 mg/kg NPS2143 group than in the OVA +5 mg/kg NPS2143 group. Furthermore, NPS2143 reduced the production of OVA-specific IgE and IgG1 in serum and the number of eosinophils and lymphocytes in BALF in OVA mice with reduced CaSR expression in lung tissues. Besides, OVA-induced mice exhibited peribronchial and perivascular inflammatory cell infiltration, which was accompanied by severe goblet cell hyperplasia/hyperplasia and airway mucus hypersecretion. Furthermore, these mice exhibited increased levels of Interleukin (IL)-5, IL-13, MCP-1, and eotaxin, which were alleviated by NPS2143. The 5 mg/kg NPS2143 showed more effective than the 2.5 mg/kg treatment. CaSR expression was elevated in the lung tissues of OVA-induced asthmatic juvenile mice, whereas the CaSR antagonist NPS2143 reduced AHR and attenuated the inflammatory response in OVA-induced juvenile mice, possibly exerting therapeutic effects on childhood asthma.

The calcium-sensing receptor in inflammation: Recent updates

The Calcium-Sensing Receptor (CaSR) is a member of the class C of G-proteins coupled receptors (GPCRs), it plays a pivotal role in calcium homeostasis by directly controlling calcium excretion in the kidneys and indirectly by regulating parathyroid hormone (PTH) release from the parathyroid glands. The CaSR is found to be ubiquitously expressed in the body, playing a plethora of additional functions spanning from fluid secretion, insulin release, neuronal development, vessel tone to cell proliferation and apoptosis, to name but a few. The present review aims to elucidate and clarify the emerging regulatory effects that the CaSR plays in inflammation in several tissues, where it mostly promotes pro-inflammatory responses, with the exception of the large intestine, where contradictory roles have been recently reported. The CaSR has been found to be expressed even in immune cells, where it stimulates immune response and chemokinesis. On the other hand, CaSR expression seems to be boosted under inflammatory stimulus, in particular, by pro-inflammatory cytokines. Because of this, the CaSR has been addressed as a key factor responsible for hypocalcemia and low levels of PTH that are commonly found in critically ill patients under sepsis or after burn injury. Moreover, the CaSR has been found to be implicated in autoimmune-hypoparathyroidism, recently found also in patients treated with immune-checkpoint inhibitors. Given the tight bound between the CaSR, calcium and vitamin D metabolism, we also speculate about their roles in the pathogenesis of severe acute respiratory syndrome coronavirus-19 (SARS-COVID-19) infection and their impact on patients' prognosis. We will further explore the therapeutic potential of pharmacological targeting of the CaSR for the treatment and management of aberrant inflammatory responses.

Elevation of spermine remodels immunosuppressive microenvironment through driving the modification of PD-L1 in hepatocellular carcinoma

Background

Spermine is frequently elevated in tumor tissues and body fluids of cancer patients and is critical for cancer cell proliferation, migration and invasion. However, the immune functions of spermine in hepatocellular carcinoma progression remains unknown. In the present study, we aimed to elucidate immunosuppressive role of spermine in hepatocellular carcinoma and to explore the underlying mechanism.

Methods

Whole-blood spermine concentration was measured using HPLC. Human primary HCC tissues were collected to examine the expression of CaSR, p-Akt, β-catenin, STT3A, PD-L1, and CD8. Mouse model of tumorigenesis and lung metastasis were established to evaluate the effects of spermine on hepatocellular carcinoma. Western blotting, immunofluorescence, real time PCR, digital Ca2+ imaging, and chromatin immunoprecipitation assay were used to investigate the underlying mechanisms by which spermine regulates PD-L1 expression and glycosylation in hepatocellular carcinoma cells.

Results

Blood spermine concentration in the HCC patient group was significantly higher than that in the normal population group. Spermine could facilitate tumor progression through inducing PD-L1 expression and decreasing the CD8+ T cell infiltration in HCC. Mechanistically, spermine activates calcium-sensing receptor (CaSR) to trigger Ca2+ entry and thereby promote Akt-dependent β-catenin stabilization and nuclear translocation. Nuclear β-catenin induced by spermine then activates transcriptional expression of PD-L1 and N-glycosyltransferase STT3A, while STT3A in turn increases the stability of PD-L1 through inducing PD-L1 protein N-glycosylation in HCC cells.

Conclusions

This study reveals the crucial function of spermine in establishing immune privilege by increasing the expression and N-glycosylation of PD-L1, providing a potential strategy for the treatment of hepatocellular carcinoma.

Higher serum albumin-corrected calcium levels are associated with revascularization and poor outcome after mechanical thrombectomy

Background

Serum calcium abnormalities have been determined to be associated with the risk and outcome of stroke. The aim of the present study was to examine the associations of serum calcium with vascular recanalization, symptomatic intracranial haemorrhage and functional outcome in stroke patients after mechanical thrombectomy.

Methods

A total of 192 patients treated with mechanical thrombectomy for anterior circulation large vessel occlusion were consecutively included from August 2017 to June 2021. Serum calcium levels were measured on admission, and albumin-corrected calcium levels were calculated for subsequent analysis. Successful arterial revascularization was defined as a modified Thrombolysis in Cerebral Infarction scale score ≥ 2b. Symptomatic intracranial haemorrhage was assessed according to the European Cooperative Acute Stroke Study (ECASS) III criteria. Poor functional outcome was defined as a modified Rankin Scale score > 2 at 3 months.

Results

Patients with poor outcomes had higher albumin-corrected calcium levels than patients with good outcomes before (2.20 (2.10, 2.30) mmol/L vs. 2.13 (2.04, 2.24) mmol/L, P = 0.002), and after adjusting for other factors (AOR 95% CI, 1.812 (1.253, 2.621), P = 0.002). Patients with unsuccessful recanalization had higher albumin-corrected calcium levels than those with recanalization (2.26 (2.09, 2.46) mmol/L vs. 2.17 (2.07, 2.27) mmol/L, P = 0.029), and after adjusting for other factors (AOR 95% CI, 2.068 (1.214, 3.524)), P = 0.008). No association was found between albumin-corrected calcium and symptomatic intracranial haemorrhage.

Conclusions

Higher serum albumin-corrected calcium levels are independently associated with revascularization and poor outcome in stroke patients after mechanical thrombectomy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02856-2.

Danger-Sensing/Patten Recognition Receptors and Neuroinflammation in Alzheimer's Disease

Fibrillar aggregates and soluble oligomers of both Amyloid-β peptides (Aβs) and hyperphosphorylated Tau proteins (p-Tau-es), as well as a chronic neuroinflammation are the main drivers causing progressive neuronal losses and dementia in Alzheimer’s disease (AD). However, the underlying pathogenetic mechanisms are still much disputed. Several endogenous neurotoxic ligands, including Aβs, and/or p-Tau-es activate innate immunity-related danger-sensing/pattern recognition receptors (PPRs) thereby advancing AD’s neuroinflammation and progression. The major PRR families involved include scavenger, Toll-like, NOD-like, AIM2-like, RIG-like, and CLEC-2 receptors, plus the calcium-sensing receptor (CaSR). This quite intricate picture stresses the need to identify the pathogenetically topmost Aβ-activated PRR, whose signaling would trigger AD’s three main drivers and their intra-brain spread. In theory, the candidate might belong to any PRR family. However, results of preclinical studies using in vitro nontumorigenic human cortical neurons and astrocytes and in vivo AD-model animals have started converging on the CaSR as the pathogenetically upmost PRR candidate. In fact, the CaSR binds both Ca²⁺ and Aβs and promotes the spread of both Ca²⁺ dyshomeostasis and AD’s three main drivers, causing a progressive neurons’ death. Since CaSR’s negative allosteric modulators block all these effects, CaSR’s candidacy for topmost pathogenetic PRR has assumed a growing therapeutic potential worth clinical testing.