Recent Advances in Pain Management: Relevant Protein Kinases and Their Inhibitors

Synthesis and biological research of new imidazolone-sulphonamide-pyrimidine hybrids as potential EGFR-TK inhibitors and apoptosis-inducing agents

Development of new effective EGFR-targeted antitumor agents is needed because of their clinical significance. A new series of imidazolone-sulphonamide-pyrimidine hybrids was designed and synthesized as modified analogs of some reported EGFR inhibitors. The cytotoxic activity of all the synthesized hybrids was investigated against the breast MCF-7 cancerous cell line using doxorubicin (Dox) as a positive control. 4-(Furan-2-ylmethylene)imidazolone-sulphonamide-pyrimidine 6b had the best potent activity against MCF-7 cells with IC50 result of 1.05 μM, which was better than Dox (IC50 = 1.91 μM). In addition, mechanistic studies revealed the ability of compounds 5g, 5h and 6b to inhibit EGFR kinase. Cell cycle analysis revealed that compound 6b can halt MCF-7 cells at the G1 phase with a concomitant decrease in cellular percentage at the S and G2/M phases. This compound produced a noticeable rise in the proportion of apoptotic cells with regard to the untreated control. Furthermore, the effects of hybrid 6b on the expression levels of pro-apoptotic Bax and pro-survival Bcl2 were assessed. The results showed that this compound upregulated the level of Bax expression as well as declined the expression value of Bcl-2 with regard to the untreated control.

Pathology of pain and its implications for therapeutic interventions

Pain is estimated to affect more than 20% of the global population, imposing incalculable health and economic burdens. Effective pain management is crucial for individuals suffering from pain. However, the current methods for pain assessment and treatment fall short of clinical needs. Benefiting from advances in neuroscience and biotechnology, the neuronal circuits and molecular mechanisms critically involved in pain modulation have been elucidated. These research achievements have incited progress in identifying new diagnostic and therapeutic targets. In this review, we first introduce fundamental knowledge about pain, setting the stage for the subsequent contents. The review next delves into the molecular mechanisms underlying pain disorders, including gene mutation, epigenetic modification, posttranslational modification, inflammasome, signaling pathways and microbiota. To better present a comprehensive view of pain research, two prominent issues, sexual dimorphism and pain comorbidities, are discussed in detail based on current findings. The status quo of pain evaluation and manipulation is summarized. A series of improved and innovative pain management strategies, such as gene therapy, monoclonal antibody, brain-computer interface and microbial intervention, are making strides towards clinical application. We highlight existing limitations and future directions for enhancing the quality of preclinical and clinical research. Efforts to decipher the complexities of pain pathology will be instrumental in translating scientific discoveries into clinical practice, thereby improving pain management from bench to bedside.

The Neglected Sibling: NLRP2 Inflammasome in the Nervous System

While classical NOD-like receptor pyrin domain containing protein 1 (NLRP1) and NLRP3 inflammasomal proteins have been extensively investigated, the contribution of NLRP2 is still ill-defined in the nervous system. Given the putative significance of NLRP2 in orchestrating neuroinflammation, further inquiry is needed to gain a better understanding of its connectome, hence its specific targeting may hold a promising therapeutic implication. Therefore, bioinformatical approach for extracting information, specifically in the context of neuropathologies, is also undoubtedly preferred. To the best of our knowledge, there is no review study selectively targeting only NLRP2. Increasing, but still fragmentary evidence should encourage researchers to thoroughly investigate this inflammasome in various animal- and human models. Taken together, herein we aimed to review the current literature focusing on the role of NLRP2 inflammasome in the nervous system and more importantly, we provide an algorithm-based protein network of human NLRP2 for elucidating potentially valuable molecular partnerships that can be the beginning of a new discourse and future therapeutic considerations.

Role of EPAC1 in chronic pain

Chronic pain usually lasts over three months and commonly occurs in chronic diseases (cancer, arthritis, and diabetes), injuries (herniated discs, torn ligaments), and many major pain disorders (neuropathic pain, fibromyalgia, chronic headaches). Unfortunately, there is currently a lack of effective treatments to help people with chronic pain to achieve complete relief. Therefore,it is particularly important to understand the mechanism of chronic pain and find new therapeutic targets. The exchange protein directly activated by cyclic adenosine monophosphate(cAMP) (EPAC) has been recognized for its functions in nerve regeneration, stimulating insulin release, controlling vascular pressure, and controlling other metabolic activities. In recent years, many studies have found that the subtype of EPAC, EPAC1 is involved in the regulation of neuroinflammation and plays a crucial role in the regulation of pain, which is expected to become a new therapeutic target for chronic pain. This article reviews the major contributions of EPAC1 in chronic pain.

Machine learning-based evaluation of spontaneous pain and analgesics from cellular calcium signals in the mouse primary somatosensory cortex using explainable features

Introduction

Pain that arises spontaneously is considered more clinically relevant than pain evoked by external stimuli. However, measuring spontaneous pain in animal models in preclinical studies is challenging due to methodological limitations. To address this issue, recently we developed a deep learning (DL) model to assess spontaneous pain using cellular calcium signals of the primary somatosensory cortex (S1) in awake head-fixed mice. However, DL operate like a "black box", where their decision-making process is not transparent and is difficult to understand, which is especially evident when our DL model classifies different states of pain based on cellular calcium signals. In this study, we introduce a novel machine learning (ML) model that utilizes features that were manually extracted from S1 calcium signals, including the dynamic changes in calcium levels and the cell-to-cell activity correlations.

Method

We focused on observing neural activity patterns in the primary somatosensory cortex (S1) of mice using two-photon calcium imaging after injecting a calcium indicator (GCaMP6s) into the S1 cortex neurons. We extracted features related to the ratio of up and down-regulated cells in calcium activity and the correlation level of activity between cells as input data for the ML model. The ML model was validated using a Leave-One-Subject-Out Cross-Validation approach to distinguish between non-pain, pain, and drug-induced analgesic states.

Results and discussion

The ML model was designed to classify data into three distinct categories: non-pain, pain, and drug-induced analgesic states. Its versatility was demonstrated by successfully classifying different states across various pain models, including inflammatory and neuropathic pain, as well as confirming its utility in identifying the analgesic effects of drugs like ketoprofen, morphine, and the efficacy of magnolin, a candidate analgesic compound. In conclusion, our ML model surpasses the limitations of previous DL approaches by leveraging manually extracted features. This not only clarifies the decision-making process of the ML model but also yields insights into neuronal activity patterns associated with pain, facilitating preclinical studies of analgesics with higher potential for clinical translation.

An Update on Protein Kinases as Therapeutic Targets-Part I: Protein Kinase C Activation and Its Role in Cancer and Cardiovascular Diseases

Protein kinases are one of the most significant drug targets in the human proteome, historically harnessed for the treatment of cancer, cardiovascular disease, and a growing number of other conditions, including autoimmune and inflammatory processes. Since the approval of the first kinase inhibitors in the late 1990s and early 2000s, the field has grown exponentially, comprising 98 approved therapeutics to date, 37 of which were approved between 2016 and 2021. While many of these small-molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP binding pocket have been massively successful for oncological indications, their poor selectively for protein kinase isozymes have limited them due to toxicities in their application to other disease spaces. Thus, recent attention has turned to the use of alternative allosteric binding mechanisms and improved drug platforms such as modified peptides to design protein kinase modulators with enhanced selectivity and other pharmacological properties. Herein we review the role of different protein kinase C (PKC) isoforms in cancer and cardiovascular disease, with particular attention to PKC-family inhibitors. We discuss translational examples and carefully consider the advantages and limitations of each compound (Part I). We also discuss the recent advances in the field of protein kinase modulators, leverage molecular docking to model inhibitor-kinase interactions, and propose mechanisms of action that will aid in the design of next-generation protein kinase modulators (Part II).

Neuropathic pain: From actual pharmacological treatments to new therapeutic horizons

Neuropathic pain, caused by a lesion or disease affecting the somatosensory system, affects between 3 and 17% of the general population. The treatment of neuropathic pain is challenging due to its heterogeneous etiologies, lack of objective diagnostic tools and resistance to classical analgesic drugs. First-line treatments recommended by the Special Interest Group on Neuropathic Pain (NeuPSIG) and European Federation of Neurological Societies (EFNS) include gabapentinoids, tricyclic antidepressants (TCAs) and selective serotonin noradrenaline reuptake inhibitors (SNRIs). Nevertheless these treatments have modest efficacy or dose limiting side effects. There is therefore a growing number of preclinical and clinical studies aim at developing new treatment strategies to treat neuropathic pain with better efficacy, selectivity, and less side effects. In this review, after a brief description of the mechanisms of action, efficacy, and limitations of current therapeutic drugs, we reviewed new preclinical and clinical targets currently under investigation, as well as promising non-pharmacological alternatives and their potential co-use with pharmacological treatments.

NS5806 inhibits ERK activation to attenuate pain induced by peripheral nerve injury

Neuropathic pain is a serious health problem, but optimal drug treatments remain lacking. It has been known that the compound NS5806 is a Kv4.3 activator, which increases Kv4.3-mediated K⁺ current to reduce neuronal excitability. In this study, we investigated the molecular and cellular mechanisms underlying the analgesic effect of NS5806 in neuropathic pain induced by peripheral nerve injury. Using lumbar (L)5/L6 spinal nerve ligation (SNL) in rats, we found that, without changing the basal nociception, the analgesic effect of NS5806 (220 μg/kg) peaked at 4 h and lasted for 8 h after intraperitoneal injection. Multiple doses of NS5806 reduced not only SNL-upregulated proinflammatory mediators in the DRG and spinal cord on day 1 and day 4 after L5/L6 SNL, but also SNL-evoked expansion of DRG macrophages and spinal microglia on day 4. Furthermore, at 10 min after L5 SNL, NS5806 pretreatment for 4 h suppressed SNL-induced phosphorylated extracellular signal-regulated kinase (pERK) in both Kv4.3⁺ and Kv4.3^- neurons in the dorsal root ganglion (DRG) and superficial spinal dorsal horn, indicating that the action of NS5806 is not restricted to Kv4.3⁺ neurons. In vitro kinase activity assays revealed that NS5806 weakly inhibited ERK2, MEK1, MEK2, and c-Raf in the ERK pathway. Since NS5806 and the ERK pathway inhibitors have similar antinociceptive characteristics, this study suggests that NS5806 also acts as an ERK pathway inhibitor to attenuate neuropathic pain.

Synthesis and Kinase Inhibitory Potencies of Pyrazolo[3,4-g]isoquinolines

A new series of pyrazolo[3,4-g]isoquinoline derivatives, diversely substituted at the 4- or 8-position, were synthesized. The results of the kinase inhibitory potency study demonstrated that the introduction of a bromine atom at the 8-position was detrimental to Haspin inhibition, while the introduction of an alkyl group at the 4-position led to a modification of the kinase inhibition profiles. Altogether, the results obtained demonstrated that new pyrazolo[3,4-g]isoquinolines represent a novel family of kinase inhibitors with various selectivity profiles.

Structural Insights Support Targeting ASK1 Kinase for Therapeutic Interventions

Apoptosis signal-regulating kinase (ASK) 1, a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family, modulates diverse responses to oxidative and endoplasmic reticulum (ER) stress and calcium influx. As a crucial cellular stress sensor, ASK1 activates c-Jun N-terminal kinases (JNKs) and p38 MAPKs. Their excessive and sustained activation leads to cell death, inflammation and fibrosis in various tissues and is implicated in the development of many neurological disorders, such as Alzheimer’s, Parkinson’s and Huntington disease and amyotrophic lateral sclerosis, in addition to cardiovascular diseases, diabetes and cancer. However, currently available inhibitors of JNK and p38 kinases either lack efficacy or have undesirable side effects. Therefore, targeted inhibition of their upstream activator, ASK1, stands out as a promising therapeutic strategy for treating such severe pathological conditions. This review summarizes recent structural findings on ASK1 regulation and its role in various diseases, highlighting prospects for ASK1 inhibition in the treatment of these pathologies.

Improved potency of pyridin-2(1H)one derivatives for the treatment of mechanical allodynia

Mechanical allodynia, a painful sensation caused by innocuous touch, is a major chronic pain symptom, which often remains without an effective treatment. There is thus a need for new anti-allodynic treatments based on new drug classes. We recently synthetized new 3,5-disubstituted pyridin-2(1H)-one derivatives. By substituting the pyridinone at the 3-position by various aryl/heteroaryl moieties and at the 5-position by a phenylamino group, we discovered that some derivatives exhibited a strong anti-allodynic potency in rats. Here, we report that varying the substitution of the pyridinone 5-position, the 3-position being substituted by an indol-4-yl moiety, further improves such anti-allodynic potency. Compared with 2, one of the two most active compounds of the first series, eleven out of nineteen newly synthetized compounds showed higher anti-allodynic potency, with two of them completely preventing mechanical allodynia. In the first series, hit compounds 1 and 2 appeared to be inhibitors of p38α MAPK, a protein kinase known to underlie pain hypersensitivity in animal models. Depending on the substitution at the 5-position, some newly synthetized compounds were also stronger p38α MAPK inhibitors. Surprisingly, though, anti-allodynic effects and p38α MAPK inhibitory potencies were not correlated, suggesting that other biological target(s) is/are involved in the analgesic activity in this series. Altogether, these results confirm that 3,5-disubstituted pyridine-2(1H)-one derivatives are of high interest for the development of new treatment of mechanical allodynia.

Corydalis saxicola Bunting total alkaloids attenuate paclitaxel-induced peripheral neuropathy through PKCε/p38 MAPK/TRPV1 signaling pathway

Background

Corydalis saxicola Bunting, affiliated with the Papaveraceae Juss., has been proven to work well in anti-inflammation, hemostasis, and analgesia. This study was designed to observe the effect and potential mechanism of Corydalis saxicola Bunting total alkaloids (CSBTA) on paclitaxel-induced peripheral neuropathy (PIPN).

Materials and methods

Rats were injected 2 mg/kg paclitaxel 4 times and administrated with 30 or 120 mg/kg CSBTA. Mechanical and thermal allodynia and hyperalgesia were tested. After 40 days, serum was collected to detect PGE2, TNF-α, and IL-1β by ELISA. The L4-L6 segment spinal cord, DRG, and plantar skin were harvested, and Western-blot or RT-qPCR analyzed protein and gene levels of pro-inflammatory cytokines, p38 MAPK, PKCε, and TRPV1. The PIPN cell model was established with paclitaxel (300 nM, 5 d) in primary DRG neurons. We examined the effect of CSBTA (25 μg/ml or 50 μg/ml) by measuring the mRNA levels in PGE2, TNF-α and CGRP, and the protein expression on the PKCε/p38 MAPK/TRPV1 signaling pathway in the PIPN cell model.

Results

The results showed that CSBTA effectively ameliorated allodynia and hyperalgesia, and regulated cytokines' contents (PGE2, TNF-α, and IL-1β) and neuropeptides (CGRP and SP) in different tissues in vivo. In addition, CSBTA significantly decreased cytokine gene levels of DRG neurons (PGE2, TNF-α, and CGRP) and the protein expressions of PKCε/p38 MAPK/TRPV1 signaling pathway in vivo and in vitro.

Conclusion

Therefore, CSBTA has a perspective therapeutic effect on the treatment of paclitaxel-induced peripheral neuropathy.