A Role for The P2Y1 Receptor in Nonsynaptic Cross-depolarization in the Rat Dorsal Root Ganglia

Feelings Are the Source of Consciousness

In this view, we address the problem of consciousness, and although we focus on its human presentation, we note that the phenomenon is present in numerous nonhuman species and use findings from a variety of animal studies to explain our hypothesis for how consciousness is made. Consciousness occurs when mind contents, such as perceptions and thoughts, are spontaneously identified as belonging to a specific organism/owner. Conscious minds are said to have a self that experiences mental events. We hypothesize that the automatic identification that associates minds and organisms is provided by a continuous flow of homeostatic feelings. Those feelings arise from the uninterrupted process of life regulation and correspond to both salient physiological fluctuations such as hunger, pain, well-being, or malaise, as well as to states closer to metabolic equilibrium and best described as feelings of life/existence, such as breathing or body temperature. We also hypothesize that homeostatic feelings were the inaugural phenomena of consciousness in biological evolution and venture that they were selected because the information they provided regarding the current state of life regulation conferred extraordinary advantages to the organisms so endowed. The "knowledge" carried by conscious homeostatic feelings provided "overt" guidance for life regulation, an advance over the covert regulation present in nonconscious organisms. Finally, we outline a mechanism for the generation of feelings based on a two-way interaction between interoceptive components of the nervous system and a particular set of nonneural components of the organism's interior, namely, viscera and circulating chemical molecules involved in their operations. Feelings emerge from this interaction as continuous and hybrid phenomena, related simultaneously to two series of events. The first is best described by the terms neural/representational/and mental and the second by the terms nonneural/visceral/and chemical. We note that this account offers a solution for the mind-body problem: homeostatic feelings constitute the "mental" version of bodily processes.

Peripheral mechanisms of chronic pain

Acutely, pain serves to protect us from potentially harmful stimuli, however damage to the somatosensory system can cause maladaptive changes in neurons leading to chronic pain. Although acute pain is fairly well controlled, chronic pain remains difficult to treat. Chronic pain is primarily a neuropathic condition, but studies examining the mechanisms underlying chronic pain are now looking beyond afferent nerve lesions and exploring new receptor targets, immune cells, and the role of the autonomic nervous system in contributing chronic pain conditions. The studies outlined in this review reveal how chronic pain is not only confined to alterations in the nervous system and presents findings on new treatment targets and for this debilitating disease.

How Is Peripheral Injury Signaled to Satellite Glial Cells in Sensory Ganglia?

Injury or inflammation in the peripheral branches of neurons of sensory ganglia causes changes in neuronal properties, including excessive firing, which may underlie chronic pain. The main types of glial cell in these ganglia are satellite glial cells (SGCs), which completely surround neuronal somata. SGCs undergo activation following peripheral lesions, which can enhance neuronal firing. How neuronal injury induces SGC activation has been an open question. Moreover, the mechanisms by which the injury is signaled from the periphery to the ganglia are obscure and may include electrical conduction, axonal and humoral transport, and transmission at the spinal level. We found that peripheral inflammation induced SGC activation and that the messenger between injured neurons and SGCs was nitric oxide (NO), acting by elevating cyclic guanosine monophosphate (cGMP) in SGCs. These results, together with work from other laboratories, indicate that a plausible (but not exclusive) mechanism for neuron-SGCs interactions can be formulated as follows: Firing due to peripheral injury induces NO formation in neuronal somata, which diffuses to SGCs. This stimulates cGMP synthesis in SGCs, leading to their activation and to other changes, which contribute to neuronal hyperexcitability and pain. Other mediators such as proinflammatory cytokines probably also contribute to neuron-SGC communications.

The Key Genes Underlying Pathophysiology Association between Plaque Instability and Progression of Myocardial Infarction

Young patients with type 2 diabetes and myocardial infarction (MI) have higher long-term all-cause and cardiovascular mortality. In addition, the observed increased, mildly abnormal baseline lipid levels, but not lipid variability, are associated with an increased risk of atherosclerotic cardiovascular disease events, particularly MI. This study investigated differentially expressed genes (DEGs), which might be potential targets for young patients with MI and a high-fat diet (HFD). GSE114695 and GSE69187 were downloaded and processed using the limma package. A Venn diagram was applied to identify the same DEGs, and further pathway analysis was performed using Metascape. Protein-protein interaction (PPI) network analysis was then applied, and the hub genes were screened out. Pivotal miRNAs were predicted and validated using the miRNA dataset in GSE114695. To investigate the cardiac function of the screened genes, an MI mouse model, echocardiogram, and ELISA of hub genes were applied, and a correlation analysis was also performed. From aged mice fed HFD, 138 DEGs were extracted. From aged mice fed with chow, 227 DEGs were extracted. Pathway enrichment analysis revealed that DEGs in aging mice fed HFD were enriched in lipid transport and lipid biosynthetic process 1 d after MI and in the MAPK signaling pathway at 1 w after MI, suggesting that HFD has less effect on aging with MI. A total of 148 DEGs were extracted from the intersection between plaques fed with HFD and chow in young mice and MI_1d, respectively, which demonstrated increased inflammatory and adaptive immune responses, in addition to myeloid leukocyte activation. A total of 183 DEGs were screened out between plaques fed with HFD vs. chow in young mice and MI_1w, respectively, which were mainly enriched in inflammatory response, cytokine production, and myeloid leukocyte activation. After validation, PAK3, CD44, CD5, SOCS3, VAV1, and PIK3CD were demonstrated to be negatively correlated with LVEF; however, P2RY1 was demonstrated to be positively correlated. This study demonstrated that the screened hub genes may be therapeutic targets for treating STEMI patients and preventing MI recurrence, especially in young MI patients with HFD or diabetes.

Interoception and the origin of feelings: A new synthesis

Feelings are conscious mental events that represent body states as they undergo homeostatic regulation. Feelings depend on the interoceptive nervous system (INS), a collection of peripheral and central pathways, nuclei and cortical regions which continuously sense chemical and anatomical changes in the organism. How such humoral and neural signals come to generate conscious mental states has been a major scientific question. The answer proposed here invokes (1) several distinctive and poorly known physiological features of the INS; and (2) a unique interaction between the body (the 'object' of interoception) and the central nervous system (which generates the 'subject' of interoception). The atypical traits of the INS and the direct interactions between neural and non-neural physiological compartments of the organism, neither of which is present in exteroceptive systems, plausibly explain the qualitative and subjective aspects of feelings, thus accounting for their conscious nature.

How do neurons in sensory ganglia communicate with satellite glial cells?

Neurons and satellite glial cells (SGCs) in sensory ganglia maintain bidirectional communications that are believed to be largely mediated by chemical messengers. Nerve injury leads to SGC activation, which was proposed to be mediated by nitric oxide (NO) released from active neurons, but evidence for this is lacking. Here we tested the idea that increased neuronal firing is a major factor in NO release. We activated neurons in isolated dorsal root and trigeminal ganglia from mice with capsaicin (5 µM), which acts on transient receptor potential vanilloid type 1 (TRPV1) channels in small neurons. We found that capsaicin induced SGC activation, as assayed by glial fibrillary acidic protein (GFAP) upregulation, and an NO-donor had a similar effect. Incubating the ganglia in capsaicin in the presence of the NO-synthase inhibitor L-NAME (100 µM) prevented the GFAP upregulation. We also found that capsaicin caused an increase in SGC-SGC coupling, which was shown previously to accompany SGC activation. To test the contribution of ATP to the actions of capsaicin, we incubated the ganglia with capsaicin in the presence of P2 purinergic receptor inhibitor suramin (100 µM), which prevented the capsaicin-induced GFAP upregulation. Size analysis indicated that although capsaicin acts mainly on small neurons, SGCs around neurons of all sizes were affected by capsaicin, suggesting a spread of signals from small neurons to neighboring cells. We conclude that neuronal excitation leads to NO release, which induces SGCs activation. It appears that ATP participates in NO's action, possibly by interaction with TRPV1 channels.

P2Y1 Receptor Agonist Attenuates Cardiac Fibroblasts Activation Triggered by TGF-β1

Cardiac fibroblasts (CFs) activation is a hallmark feature of cardiac fibrosis caused by cardiac remodeling. The purinergic signaling molecules have been proven to participate in the activation of CFs. In this study, we explored the expression pattern of P2Y receptor family in the cardiac fibrosis mice model induced by the transverse aortic constriction (TAC) operation and in the activation of CFs triggered by transforming growth factor β1 (TGF-β1) stimulation. We then investigated the role of P2Y1receptor (P2Y1R) in activated CFs. The results showed that among P2Y family members, only P2Y1R was downregulated in the heart tissues of TAC mice. Consistent with our in vivo results, the level of P2Y1R was decreased in the activated CFs, when CFs were treated with TGF-β1. Silencing P2Y1R expression with siP2Y1R accelerated the effects of TGF-β1 on CFs activation. Moreover, the P2Y1R selective antagonist BPTU increased the levels of mRNA and protein of profibrogenic markers, such as connective tissue growth factor (CTGF), periostin (POSTN). periostin (POSTN), and α-smooth muscle actin(α-SMA). Further, MRS2365, the agonist of P2Y1R, ameliorated the activation of CFs and activated the p38 MAPK and ERK signaling pathways. In conclusion , our findings revealed that upregulating of P2Y1R may attenuate the abnormal activation of CFs via the p38 MAPK and ERK signaling pathway.

Emerging importance of satellite glia in nervous system function and dysfunction

Satellite glial cells (SGCs) closely envelop cell bodies of neurons in sensory, sympathetic and parasympathetic ganglia. This unique organization is not found elsewhere in the nervous system. SGCs in sensory ganglia are activated by numerous types of nerve injury and inflammation. The activation includes upregulation of glial fibrillary acidic protein, stronger gap junction-mediated SGC-SGC and neuron-SGC coupling, increased sensitivity to ATP, downregulation of Kir4.1 potassium channels and increased cytokine synthesis and release. There is evidence that these changes in SGCs contribute to chronic pain by augmenting neuronal activity and that these changes are consistent in various rodent pain models and likely also in human pain. Therefore, understanding these changes and the resulting abnormal interactions of SGCs with sensory neurons could provide a mechanistic approach that might be exploited therapeutically in alleviation and prevention of pain. We describe how SGCs are altered in rodent models of four common types of pain: systemic inflammation (sickness behaviour), post-surgical pain, diabetic neuropathic pain and post-herpetic pain.