Cobra neurotoxin produces central analgesic and hyperalgesic actions via adenosine A1 and A2A receptors

Unveiling the Pain Relief Potential: Harnessing Analgesic Peptides from Animal Venoms

The concept of pain encompasses a complex interplay of sensory and emotional experiences associated with actual or potential tissue damage. Accurately describing and localizing pain, whether acute or chronic, mild or severe, poses a challenge due to its diverse manifestations. Understanding the underlying origins and mechanisms of these pain variations is crucial for effective management and pharmacological interventions. Derived from a wide spectrum of species, including snakes, arthropods, mollusks, and vertebrates, animal venoms have emerged as abundant repositories of potential biomolecules exhibiting analgesic properties across a broad spectrum of pain models. This review focuses on highlighting the most promising venom-derived toxins investigated as potential prototypes for analgesic drugs. The discussion further encompasses research prospects, challenges in advancing analgesics, and the practical application of venom-derived toxins. As the field continues its evolution, tapping into the latent potential of these natural bioactive compounds holds the key to pioneering approaches in pain management and treatment. Therefore, animal toxins present countless possibilities for treating pain caused by different diseases. The development of new analgesic drugs from toxins is one of the directions that therapy must follow, and it seems to be moving forward by recommending the composition of multimodal therapy to combat pain.

Adenosine signaling mediate pain transmission in the central nervous system

Pain is a common clinical symptom that seriously affects the quality of life in a variety of patient populations. In recent years, research on the role of adenosine signaling in pain modulation has made great progress. Adenosine is a purine nucleoside and a neuromodulator, and regulates multiple physiological and pathophysiological functions through the activation of four G protein-coupled receptors, which are classified as A₁, A_2A, A_2B, and A₃ adenosine receptors (ARs). Adenosine and its receptors that are widespread in the central nervous system (CNS) play an important role in the processing of nociceptive sensory signals in different pain models. A₁Rs have the highest affinity to adenosine, and the role in analgesia has been well investigated. The roles of A_2ARs and A_2BRs in the modulation of pain are controversial because they have both analgesic and pronociceptive effects. The analgesic effects of A₃Rs are primarily manifested in neuropathic pain. In this article, we have reviewed the recent studies on ARs in the modulation of neuropathic pain, inflammatory pain, postoperative pain, and visceral pain in the CNS. Furthermore, we have outlined the pathways through which ARs contribute to pain regulation, thereby shedding light on how this mechanism can be targeted to provide effective pain relief.

Neurotoxins Acting at Synaptic Sites: A Brief Review on Mechanisms and Clinical Applications

Neurotoxins generally inhibit or promote the release of neurotransmitters or bind to receptors that are located in the pre- or post-synaptic membranes, thereby affecting physiological functions of synapses and affecting biological processes. With more and more research on the toxins of various origins, many neurotoxins are now widely used in clinical treatment and have demonstrated good therapeutic outcomes. This review summarizes the structural properties and potential pharmacological effects of neurotoxins acting on different components of the synapse, as well as their important clinical applications, thus could be a useful reference for researchers and clinicians in the study of neurotoxins.

pH-sensitive dual drug loaded janus nanoparticles by oral delivery for multimodal analgesia

Background

Based on the concept of “multimodal analgesia”, a novel dual drug delivery system was designed to achieve synergistic analgesia between najanajaatra venom protein (αCT) and resveratrol (Res). In order to meet the joint loading of two drugs with different physicochemical properties without affecting each other, an oral Janus nanoparticle (JNP) with a unique cavity structure and synergistic drug delivery was constructed using an improved double emulsion solvent evaporation method, and combined with low-molecular-weight chitosan/sodium alginate and PLGA to achieve its pH-responsive.

Results

The synthesized αCT/Res-JNPs are homogeneous in shape, with a two-compartment structure, approximately 230 nm in size, and zeta potential of 23.6 mV. Drug release assayed in vitro show that JNP was stable in simulated gastric juice (pH = 1.2) but was released in phosphate buffer saline (pH = 7.4). After intragastric administration in rats, PK evaluation showed that αCT/Res-JNPs could significantly improve the oral bioavailability, and the simultaneous encapsulation of the two drugs had no significant interaction on PK parameters. An obvious synergistic analgesic effects of αCT/Res-JNPs was confirmed in a spinal cord injury and acute pain model. Confocal laser scanning microscopy and single-pass intestinal perfusion model provided strong evidence that αCT/Res-JNPs could pass through intestinal epithelial cells, and the endocytosis pathway was mainly involved in the mediation and pinocytosis of reticulin. The concentrations of αCT and Res from αCT/Res-JNP in lymphatic transport were only about 8.72% and 6.08% of their blood concentrations at 1 h, respectively, which indicated that lymphatic transport in the form of JNP has limited advantages in improving the oral bioavailability of Res and αCT. Cellular uptake efficiency at 4 h was about 10–15% in Caco-2 cell lines for αCT/Res-JNP, but was reduced to 7% in Caco-2/HT29-MTX co-culture models due to the hindrance by the mucus layers. Approximately 12–17% of αCT/Res-JNP were transported across Caco-2/HT29-MTX/Raji monolayers. The cumulative absorption of JNP in three cell models was higher than that of free drug.

Conclusions

This study investigated the contribution of Janus nanoparticles in oral absorption, and provide a new perspective for oral administration and analgesic treatment of dual drug delivery system containing peptide drugs.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00974-6.