The stress protein heat shock cognate 70 (Hsc70) inhibits the Transient Receptor Potential Vanilloid type 1 (TRPV1) channel

Biofilm exopolysaccharides alter sensory-neuron-mediated sickness during lung infection

Infections of the lung cause observable sickness thought to be secondary to inflammation. Signs of sickness are crucial to alert others via behavioral-immune responses to limit contact with contagious individuals. Gram-negative bacteria produce exopolysaccharide (EPS) that provides microbial protection; however, the impact of EPS on sickness remains uncertain. Using genome-engineered Pseudomonas aeruginosa (P. aeruginosa) strains, we compared EPS-producers versus non-producers and a virulent Escherichia coli (E. coli) lung infection model in male and female mice. EPS-negative P. aeruginosa and virulent E. coli infection caused severe sickness, behavioral alterations, inflammation, and hypothermia mediated by TLR4 detection of the exposed lipopolysaccharide (LPS) in lung TRPV1+ sensory neurons. However, inflammation did not account for sickness. Stimulation of lung nociceptors induced acute stress responses in the paraventricular hypothalamic nuclei by activating corticotropin-releasing hormone neurons responsible for sickness behavior and hypothermia. Thus, EPS-producing biofilm pathogens evade initiating a lung-brain sensory neuronal response that results in sickness.

HSP27 Modulates Neuropathic Pain by Inhibiting P2X3 Degradation

The role of heat shock protein 27 (HSP27), a chaperone, in neuropathic pain after nerve injury has not been systematically surveyed despite its neuroprotective and regeneration-promoting effects. In this study, we found that HSP27 expression in sensory neurons of the dorsal root ganglia (DRG) mediated nerve injury-induced neuropathic pain. Neuropathic pain behaviors were alleviated by silencing HSP27 in the DRG of a rat spinal nerve ligation (SNL) model. Local injection of an HSP27-overexpression construct into the DRG of naïve rats elicited neuropathic pain behaviors. HSP27 interacted with a purinergic receptor, P2X3, and their expression patterns corroborated the induction and reversal of neuropathic pain according to two lines of evidence: colocalization immunohistochemically and immunoprecipitation biochemically. In a cell model cotransfected with HSP27 and P2X3, the degradation rate of P2X3 was reduced in the presence of HSP27. Such an alteration was mediated by reducing P2X3 ubiquitination in SNL rats and was reversed after silencing HSP27 in the DRGs of SNL rats. In summary, the interaction of HSP27 with P2X3 provides a new mechanism of injury-induced neuropathic pain that could serve as an alternative therapeutic target.

Proteome landscape and interactome of voltage-gated potassium channel 1.6 (Kv1.6) of the murine ophthalmic artery and neuroretina

The voltage-gated potassium channel 1.6 (Kv1.6) plays a vital role in ocular neurovascular beds and exerts its modulatory functions via interaction with other proteins. However, the interactome and their potential roles remain unknown. Here, the global proteome landscape of the ophthalmic artery (OA) and neuroretina was mapped, followed by the determination of Kv1.6 interactome and validation of its functionality and cellular localization. Microfluorimetric analysis of intracellular [K+] and Western blot validated the native functionality and cellular expression of the recombinant Kv1.6 channel protein. A total of 54, 9 and 28 Kv1.6-interacting proteins were identified in the mouse OA and, retina of mouse and rat, respectively. The Kv1.6-protein partners in the OA, namely actin cytoplasmic 2, alpha-2-macroglobulin and apolipoprotein A-I, were implicated in the maintenance of blood vessel integrity by regulating integrin-mediated adhesion to extracellular matrix and Ca2+ flux. Many retinal protein interactors, particularly the ADP/ATP translocase 2 and cytoskeleton protein tubulin, were involved in endoplasmic reticulum stress response and cell viability. Three common interactors were found in all samples comprising heat shock cognate 71 kDa protein, Ig heavy constant gamma 1 and Kv1.6 channel. This foremost in-depth investigation enriched and identified the elusive Kv1.6 channel and, elucidated its complex interactome.

The neuronal tyrosine kinase receptor ligand ALKAL2 mediates persistent pain

The anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase known for its oncogenic potential that is involved in the development of the peripheral and central nervous system. ALK receptor ligands ALKAL1 and ALKAL2 were recently found to promote neuronal differentiation and survival. Here, we show that inflammation or injury enhanced ALKAL2 expression in a subset of TRPV1⁺ sensory neurons. Notably, ALKAL2 was particularly enriched in both mouse and human peptidergic nociceptors, yet weakly expressed in nonpeptidergic, large-diameter myelinated neurons or in the brain. Using a coculture expression system, we found that nociceptors exposed to ALKAL2 exhibited heightened excitability and neurite outgrowth. Intraplantar CFA or intrathecal infusion of recombinant ALKAL2 led to ALK phosphorylation in the lumbar dorsal horn of the spinal cord. Finally, depletion of ALKAL2 in dorsal root ganglia or blocking ALK with clinically available compounds crizotinib or lorlatinib reversed thermal hyperalgesia and mechanical allodynia induced by inflammation or nerve injury, respectively. Overall, our work uncovers the ALKAL2/ALK signaling axis as a central regulator of nociceptor-induced sensitization. We propose that clinically approved ALK inhibitors used for non–small cell lung cancer and neuroblastomas could be repurposed to treat persistent pain conditions.

Monitoring TRPC7 Conformational Changes by BRET Following GPCR Activation

Transient receptor potential canonical (TRPC) channels are membrane proteins involved in regulating Ca²⁺ homeostasis, and whose functions are modulated by G protein-coupled receptors (GPCR). In this study, we developed bioluminescent resonance energy transfer (BRET) biosensors to better study channel conformational changes following receptor activation. For this study, two intramolecular biosensors, GFP10-TRPC7-RLucII and RLucII-TRPC7-GFP10, were constructed and were assessed following the activation of various GPCRs. We first transiently expressed receptors and the biosensors in HEK293 cells, and BRET levels were measured following agonist stimulation of GPCRs. The activation of GPCRs that engage Gα_q led to a Gα_q-dependent BRET response of the functional TRPC7 biosensor. Focusing on the Angiotensin II type-1 receptor (AT₁R), GFP10-TRPC7-RLucII was tested in rat neonatal cardiac fibroblasts, expressing endogenous AT₁R and TRPC7. We detected similar BRET responses in these cells, thus validating the use of the biosensor in physiological conditions. Taken together, our results suggest that activation of Gα_q-coupled receptors induce conformational changes in a novel and functional TRPC7 BRET biosensor.

TRP channels in COVID-19 disease: Potential targets for prevention and treatment

Coronavirus disease 2019 [COVID-19] is a global health threat caused by severe acute respiratory syndrome coronavirus 2 [SARS-CoV2] that requires two proteins for entry: angiotensin-converting enzyme 2 [ACE2] and -membrane protease serine 2 [TMPRSS2]. Many patients complain from pneumonia, cough, fever, and gastrointestinal (GI) problems. Notably, different TRP channels are expressed in various tissues infected by SARS-CoV-2. TRP channels are cation channels that show a common architecture with high permeability to calcium [Ca²⁺] in most sub-families. Literature review shed light on the possible role of TRP channels in COVID-19 disease. TRP channels may take part in inflammation, pain, fever, anosmia, ageusia, respiratory, cardiovascular, GI and neurological complications related to COVID-19. Also, TRP channels could be the targets for many active compounds that showed effectiveness against SARS-CoV-2. Desensitization or blocking TRP channels by antibodies, aptamers, small molecules or venoms can be an option for COVID-19 prevention and future treatment. This review provides insights into the involvement of TRP channels in different symptoms and mechanisms of SARS-CoV-2 , potential treatments targeting these channels and highlights missing gaps in literature.

Regeneration of mechanical sciatic nerve injury is affected by cold and heat exposure: involvements of the TRPM2 and TRPM8 channels

BACKGROUND

Mechanical sciatic nerve (MSN) injury has a high rate within trauma cases. Heat and cold exposure in the treatments of MSN injuries have been clinically used in human. The MSN injury results in apoptosis, overload Ca²⁺ influx, and reactive oxygen species (ROS) generation in the sciatic nerve. TRPM2 and TRPM8 cation channels are activated by ROS. TRPM2 is activated by warmth (36-38°C) and heat (45-47°C), although TRPM8 is activated by cold (0-25°C). Heat or cold exposure may aid recovery MSN injury through modulation of TRPM2 and TRPM8 in sciatic nerve.

OBJECTIVE

The protective roles of cold and heat treatments via modulation of TRPM2 and TRPM8 were evaluated on MSN injury-induced neurotoxicity in in vitro models of mouse and the SH-SY5Y cell line.

METHOD

The mice sciatic nerves and SH-SY5Y cells were divided into control (37°C), cold (10°C), and moderate heat (40°C) groups.

RESULTS

Our data identified a decrease in injury diameter in the neurons following heat exposure, but not cold exposure. In addition, the results of laser confocal microscopy analyses were indicative of a protective role of TRPM8 antagonist (ACA) against cold-induced increases in Ca²⁺ influx in the sciatic nerve and TRPM8 expressing SH-SY5Y cells. The results of the automatic plate reader and laser confocal microscope assays indicated a protective role of heat treatment against MSN injury-induced increases in apoptosis, mitochondrial ROS, cytosolic ROS, caspase -3, and -9 in the neurons.

CONCLUSIONS

The heat treatment via possible modulation of TRPM2 channel and heat shock proteins induced protective actions against injury-mediated increases of oxidative stress, excitotoxicity, and apoptosis in the sciatic nerve and SH-SY5Y cells.

Oxymatrine ameliorates imiquimod-induced psoriasis pruritus and inflammation through inhibiting heat shock protein 90 and heat shock protein 60 expression in keratinocytes

In this work, we aimed to investigate whether oxymatrine exerts its anti-pruritic and anti-inflammatory efficacy in the imiquimod-induced psoriasis mice and the related mechanism. We established the psoriasis model by applying the imiquimod ointment topically and oxymatrine was injected intraperitoneally as the treatment. The behavior and skin morphology results indicated that oxymatrine inhibits imiquimod-induced pruritus alleviating keratinization of skin and inflammatory infiltration. Moreover, we examined the expression of various indicators and found heat shock protein (HSP) 90 and 60 upregulated in model group, which were reversed in oxymatrine treated groups. Molecular docking and the studies in vivo confirmed that HSP90 and HSP60 participate in the inhibitory effect of oxymatrine on the phenotypes of psoriasis mice. Mechanically, immunofluorescence staining demonstrated that oxymatrine-induced downregulation of HSP90 and HSP60 was mainly in keratinocytes. In vitro results showed that oxymatrine decreases the expression of HSP90 and HSP60 upregulated by TNF-α and IFN-γ in HaCaTs cells and the siRNA mediated HSP90 and HSP60 silencing reverses inflammation inhibited by oxymatrine. Taken together, these results indicate that oxymatrine relieves psoriasis pruritic and inflammation by inhibiting the expression of HSP90 and HSP60 in keratinocytes through MAPK signaling pathway.

The newly synthesized compounds (NCHDH and NTHDH) attenuates LPS-induced septicemia and multi-organ failure via Nrf2/HO1 and HSP/TRVP1 signaling in mice

The sepsis is considered as serious clinic-pathological condition related with high rate of morbidity and mortality in critical care settings. In the proposed study, the hydrazides derivatives N-(benzylidene)-2-((2-hydroxynaphthalen-1-yl)diazenyl)benzohydrazides (1-2) (NCHDH and NTHDH) were investigated against the LPS-induced sepsis in rodents. The NCHDH and NTHDH markedly improved the physiological sign and symptoms associated with the sepsis such as mortality, temperature, and clinical scoring compared to negative control group, which received only LPS (i.p.). The NCHDH and NTHDH also inhibited the production of the NO and MPO compared to the negative control. Furthermore, the treatment control improved the histological changes markedly of all the vital organs. Additionally, the Masson's trichrome and PAS (Periodic Acid Schiff) staining also showed improvement in the NCHDH and NTHDH treated group in contrast to LPS-induced group. The antioxidants were enhanced by the intervention of the NCHDH and NTHDH and the level of the MDA and POD were attenuated marginally compared to the LPS-induced group. The hematology study showed marked improvement and the reversal of the LPS-induced changes in blood composition compared to the negative control. The synthetic function of the liver and kidney were preserved in the NCHDH and NTHDH treated group compared to the LPS-induced group. The NCHDH and NTHDH markedly enhanced the Nrf2, HO-1 (Heme oxygenase-1), while attenuated the Keap1 and TRPV1 expression level as compared to LPS treated group. Furthermore, the NCHDH and NTHDH treatment showed marked increased in the mRNA expression level of the HSP70/90 proteins compared to the negative control.

Artificial Engineered Natural Killer Cells Combined with Antiheat Endurance as a Powerful Strategy for Enhancing Photothermal-Immunotherapy Efficiency of Solid Tumors

Although photothermal therapy (PTT) is preclinically applied in solid tumor treatment, incomplete tumor removal of PTT and heat endurance of tumor cells induces significant tumor relapse after treatment, therefore lowering the therapeutic efficiency of PTT. Herein, a programmable therapeutic strategy that integrates photothermal therapeutic agents (PTAs), DNAzymes, and artificial engineered natural killer (A-NK) cells for immunotherapy of hepatocellular carcinoma (HCC) is designed. The novel PTAs, termed as Mn-CONASHs, with 2D structure are synthesized by the coordination of tetrahydroxyanthraquinone and Mn²⁺ ions. By further adsorbing polyetherimide/DNAzymes on the surface, the DNAzymes@Mn-CONASHs exhibit excellent light-to-heat conversion ability, tumor microenvironment enhanced T₁ -MRI guiding ability, and antiheat endurance ability. Furthermore, the artificial engineered NK cells with HCC specific targeting TLS11a-aptamer decoration are constructed for specifically eliminating any possible residual tumor cells after PTT, to systematically enhance the therapeutic efficacy of PTT and avoid tumor relapse. Taken together, the potential of A-NK cells combined with antiheat endurance as a powerful strategy for immuno-enhancing photothermal therapy efficiency of solid tumors is highlighted, and the current strategy might provide promising prospects for cancer therapy.

Rho GTPases in the Physiology and Pathophysiology of Peripheral Sensory Neurons

Numerous experimental studies demonstrate that the Ras homolog family of guanosine triphosphate hydrolases (Rho GTPases) Ras homolog family member A (RhoA), Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division cycle 42 (Cdc42) are important regulators in somatosensory neurons, where they elicit changes in the cellular cytoskeleton and are involved in diverse biological processes during development, differentiation, survival and regeneration. This review summarizes the status of research regarding the expression and the role of the Rho GTPases in peripheral sensory neurons and how these small proteins are involved in development and outgrowth of sensory neurons, as well as in neuronal regeneration after injury, inflammation and pain perception. In sensory neurons, Rho GTPases are activated by various extracellular signals through membrane receptors and elicit their action through a wide range of downstream effectors, such as Rho-associated protein kinase (ROCK), phosphoinositide 3-kinase (PI3K) or mixed-lineage kinase (MLK). While RhoA is implicated in the assembly of stress fibres and focal adhesions and inhibits neuronal outgrowth through growth cone collapse, Rac1 and Cdc42 promote neuronal development, differentiation and neuroregeneration. The functions of Rho GTPases are critically important in the peripheral somatosensory system; however, their signalling interconnections and partially antagonistic actions are not yet fully understood.

TRPV1 promotes opioid analgesia during inflammation

Pain and inflammation are inherently linked responses to injury, infection, or chronic diseases. Given that acute inflammation in humans or mice enhances the analgesic properties of opioids, there is much interest in determining the inflammatory transducers that prime opioid receptor signaling in primary afferent nociceptors. Here, we found that activation of the transient receptor potential vanilloid type 1 (TRPV1) channel stimulated a mitogen-activated protein kinase (MAPK) signaling pathway that was accompanied by the shuttling of the scaffold protein β-arrestin2 to the nucleus. The nuclear translocation of β-arrestin2 in turn prevented its recruitment to the μ-opioid receptor (MOR), the subsequent internalization of agonist-bound MOR, and the suppression of MOR activity that occurs upon receptor desensitization. Using the complete Freund's adjuvant (CFA) inflammatory pain model to examine the role of TRPV1 in regulating endogenous opioid analgesia in mice, we found that naloxone methiodide (Nal-M), a peripherally restricted, nonselective, and competitive opioid receptor antagonist, slowed the recovery from CFA-induced hypersensitivity in wild-type, but not TRPV1-deficient, mice. Furthermore, we showed that inflammation prolonged morphine-induced antinociception in a mouse model of opioid receptor desensitization, a process that depended on TRPV1. Together, our data reveal a TRPV1-mediated signaling pathway that serves as an endogenous pain-resolution mechanism by promoting the nuclear translocation of β-arrestin2 to minimize MOR desensitization. This previously uncharacterized mechanism may underlie the peripheral opioid control of inflammatory pain. Dysregulation of the TRPV1-β-arrestin2 axis may thus contribute to the transition from acute to chronic pain.

Injury-induced cold sensitization in Drosophila larvae involves behavioral shifts that require the TRP channel Brv1

Nociceptive sensitization involves an increase in responsiveness of pain sensing neurons to sensory stimuli, typically through the lowering of their nociceptive threshold. Nociceptive sensitization is common following tissue damage, inflammation, and disease and serves to protect the affected area while it heals. Organisms can become sensitized to a range of noxious and innocuous stimuli, including thermal stimuli. The basic mechanisms underlying sensitization to warm or painfully hot stimuli have begun to be elucidated, however, sensitization to cold is not well understood. Here, we develop a Drosophila assay to study cold sensitization after UV-induced epidermal damage in larvae. Larvae respond to acute cold stimuli with a set of unique behaviors that include a contraction of the head and tail (CT) or a raising of the head and tail into a U-Shape (US). Under baseline, non-injured conditions larvae primarily produce a CT response to an acute cold (10°C) stimulus, however, we show that cold-evoked responses shift following tissue damage: CT responses decrease, US responses increase and some larvae exhibit a lateral body roll (BR) that is typically only observed in response to high temperature and noxious mechanical stimuli. At the cellular level, class III neurons are required for the decrease in CT, chordotonal neurons are required for the increase in US, and chordotonal and class IV neurons are required for the appearance of BR responses after UV. At the molecular level, we found that the transient receptor potential (TRP) channel brivido-1 (brv1) is required for these behavioral shifts. Our Drosophila model will allow us to precisely identify the genes and circuits involved in cold nociceptive sensitization.

Identification of Chloride Channels CLCN3 and CLCN5 Mediating the Excitatory Cl- Currents Activated by Sphingosine-1-Phosphate in Sensory Neurons

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid involved in numerous physiological and pathophysiological processes. We have previously reported a S1P-induced nocifensive response in mice by excitation of sensory neurons via activation of an excitatory chloride current. The underlying molecular mechanism for the S1P-induced chloride conductance remains elusive. In the present study, we identified two CLCN voltage-gated chloride channels, CLCN3 and CLCN5, which mediated a S1P-induced excitatory Cl^- current in sensory neurons by combining RNA-seq, adenovirus-based gene silencing and whole-cell electrophysiological voltage-clamp recordings. Downregulation of CLCN3 and CLCN5 channels by adenovirus-mediated delivery of shRNA dramatically reduced S1P-induced Cl^- current and membrane depolarization in sensory neurons. The mechanism of S1P-induced activation of the chloride current involved Rho GTPase but not Rho-associated protein kinase. Although S1P-induced potentiation of TRPV1-mediated ionic currents also involved Rho-dependent process, the lack of correlation of the S1P-activated Cl^- current and the potentiation of TRPV1 by S1P suggests that CLCN3 and CLCN5 are necessary components for S1P-induced excitatory Cl^- currents but not for the amplification of TRPV1-mediated currents in sensory neurons. This study provides a novel mechanistic insight into the importance of bioactive sphingolipids in nociception.

Granulocyte-colony-stimulating factor (G-CSF) signaling in spinal microglia drives visceral sensitization following colitis

Pain is a main symptom of inflammatory diseases and often persists beyond clinical remission. Although we have a good understanding of the mechanisms of sensitization at the periphery during inflammation, little is known about the mediators that drive central sensitization. Recent reports have identified hematopoietic colony-stimulating factors as important regulators of tumor- and nerve injury-associated pain. Using a mouse model of colitis, we identify the proinflammatory cytokine granulocyte-colony-stimulating factor (G-CSF or Csf-3) as a key mediator of visceral sensitization. We report that G-CSF is specifically up-regulated in the thoracolumbar spinal cord of colitis-affected mice. Our results show that resident spinal microglia express the G-CSF receptor and that G-CSF signaling mediates microglial activation following colitis. Furthermore, healthy mice subjected to intrathecal injection of G-CSF exhibit pronounced visceral hypersensitivity, an effect that is abolished by microglial depletion. Mechanistically, we demonstrate that G-CSF injection increases Cathepsin S activity in spinal cord tissues. When cocultured with microglia BV-2 cells exposed to G-CSF, dorsal root ganglion (DRG) nociceptors become hyperexcitable. Blocking CX3CR1 or nitric oxide production during G-CSF treatment reduces excitability and G-CSF-induced visceral pain in vivo. Finally, administration of G-CSF-neutralizing antibody can prevent the establishment of persistent visceral pain postcolitis. Overall, our work uncovers a DRG neuron-microglia interaction that responds to G-CSF by engaging Cathepsin S-CX3CR1-inducible NOS signaling. This interaction represents a central step in visceral sensitization following colonic inflammation, thereby identifying spinal G-CSF as a target for treating chronic abdominal pain.