Lipid kinases as therapeutic targets for chronic pain

Association between single nucleotide variants and severe chronic pain in older adult patients after lower extremity arthroplasty

BACKGROUND

Hip or knee osteoarthritis (OA) is one of the main causes of disability worldwide and occurs mostly in the older adults. Total hip or knee arthroplasty is the most effective method to treat OA. However, severe postsurgical pain leading to a poor prognosis. So, investigating the population genetics and genes related to severe chronic pain in older adult patients after lower extremity arthroplasty is helpful to improve the quality of treatment.

METHODS

We collected blood samples from elderly patients who underwent lower extremity arthroplasty from September 2020 to February 2021 at the Drum Tower Hospital Affiliated to Nanjing University Medical School. The enrolled patients provided measures of pain intensity using the numerical rating scale on the 90th day after surgery. Patients were divided into the case group (Group A) and the control group (Group B) including 10 patients respectively by the numerical rating scale. DNA was isolated from the blood samples of the two groups for whole-exome sequencing.

RESULTS

In total, 661 variants were identified in the 507 gene regions that were significantly different between both groups (P < 0.05), including CASP5, RASGEF1A, CYP4B1, etc. These genes are mainly involved in biological processes, including cell-cell adhesion, ECM-receptor interaction, metabolism, secretion of bioactive substances, ion binding and transport, regulation of DNA methylation, and chromatin assembly.

CONCLUSIONS

The current study shows some variants within genes are significantly associated with severe postsurgical chronic pain in older adult patients after lower extremity arthroplasty, indicating a genetic predisposition for chronic postsurgical pain. The study was registered according to ICMJE guidelines. The trial registration number is ChiCTR2000031655 and registration date is April 6th, 2020.

Association of dyslipidemia with chronic non-malignant pain in elderly patients with femoral neck fractures treated by primary total hip arthroplasty: a retrospective study

OBJECTIVE

The association of chronic non-malignant pain (CNP) with dyslipidemia is unclear. This retrospective study was performed to evaluate the association between CNP and dyslipidemia in elderly patients with femoral neck fractures (FNFs) treated by primary unilateral total hip arthroplasty (THA).

METHODS

We retrospectively identified 521 consecutive patients with FNFs (AO/OTA type 31B) who underwent primary unilateral THA from 2009 to 2021. The study population was divided into patients with and without CNP. Serum lipids were measured for each patient. The association between CNP and dyslipidemia was assessed using a multivariate binary logistic regression model.

RESULTS

In total, 436 patients (220 with CNP, 216 without CNP) were eligible for analysis. In the quantile regression, the adverse effect of CNP was significantly attenuated by resilience in patients with a high high-density lipoprotein (HDL) concentration and low low-density lipoprotein (LDL) concentration. The multivariate binary logistic regression model showed that the HDL and LDL concentrations were the only variables significantly associated with the development of CNP.

CONCLUSION

Both a low HDL and high LDL concentration may result in the occurrence of CNP in elderly patients with FNFs treated by primary unilateral THA.

Conditional deletion of Pip5k1c in sensory ganglia and effects on nociception and inflammatory sensitization

Abstract

Phosphatidylinositol 4-phosphate 5-kinase type 1 gamma (Pip5k1c) generates phosphatidylinositol 4,5-bisphosphate, also known as PI(4,5)P2 or PIP2. Many pronociceptive signaling pathways and receptor tyrosine kinases signal via PIP2 hydrolysis. Previously, we found that pain signaling and pain sensitization were reduced in Pip5k1cþ/ global heterozygous knockout mice. Here, we sought to evaluate the extent to which dorsal root ganglia selective deletion of Pip5k1c affected nociception in mice. Initially, we crossed sensory neuron-selective Advillin-Cre mice with a conditional Pip5k1c knockout (cKO) allele (Pip5k1cfl/fl). However, these mice displayed an early onset proprioceptive deficit. To bypass this early onset phenotype, we used two different tamoxifen-inducible Cre lines (Brn3a-Cre-ERT2 and Advillin-Cre-ERT2) to conditionally delete Pip5k1c in adults. Tamoxifen induced high efficiency deletion of PIP5K1C in dorsal root ganglia and slightly reduced PIP5K1C in spinal cord and brain in Brn3a-Cre-ERT2 Pip5k1cfl/fl (Brn3a cKO) mice while PIP5K1C was selectively deleted in dorsal root ganglia with no changes in spinal cord or brain in Advillin-Cre-ERT2 Pip5k1cfl/fl (Advil cKO) mice. Acute thermosensation and mechanosensation were not altered in either line relative to wild-type mice. However, thermal hypersensitivity and mechanical allodynia recovered more rapidly in Brn3a cKO mice, but not Advil cKO mice, following hind paw inflammation. These data collectively suggest that PIP5K1C regulates nociceptive sensitization in more regions of the nervous system than dorsal root ganglia alone.

Human EAG channels are directly modulated by PIP2 as revealed by electrophysiological and optical interference investigations

Voltage-gated ether à go-go (EAG) K⁺ channels are expressed in various types of cancer cells and also in the central nervous system. Aberrant overactivation of human EAG1 (hEAG1) channels is associated with cancer and neuronal disorders such as Zimmermann-Laband and Temple-Baraitser syndromes. Although hEAG1 channels are recognized as potential therapeutic targets, regulation of their functional properties is only poorly understood. Here, we show that the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP₂) is a potent inhibitory gating modifier of hEAG1 channels. PIP₂ inhibits the channel activity by directly binding to a short N-terminal segment of the channel important for Ca²⁺/calmodulin (CaM) binding as evidenced by bio-layer interferometry measurements. Conversely, depletion of endogenous PIP₂ either by serotonin-induced phospholipase C (PLC) activation or by a rapamycin-induced translocation system enhances the channel activity at physiological membrane potentials, suggesting that PIP₂ exerts a tonic inhibitory influence. Our study, combining electrophysiological and direct binding assays, demonstrates that hEAG1 channels are subject to potent inhibitory modulation by multiple phospholipids and suggests that manipulations of the PIP₂ signaling pathway may represent a strategy to treat hEAG1 channel-associated diseases.

Targeting AMPK for the Alleviation of Pathological Pain

Chronic pain is a major clinical problem that is poorly treated with available therapeutics. Adenosine monophosphate-activated protein kinase (AMPK) has recently emerged as a novel target for the treatment of pain with the exciting potential for disease modification. AMPK activators inhibit signaling pathways that are known to promote changes in the function and phenotype of peripheral nociceptive neurons and promote chronic pain. AMPK activators also reduce the excitability of these cells suggesting that AMPK activators may be efficacious for the treatment of chronic pain disorders, like neuropathic pain, where changes in the excitability of nociceptors is thought to be an underlying cause. In agreement with this, AMPK activators have now been shown to alleviate pain in a broad variety of preclinical pain models indicating that this mechanism might be engaged for the treatment of many types of pain in the clinic. A key feature of the effect of AMPK activators in these models is that they can lead to a long-lasting reversal of pain hypersensitivity even long after treatment cessation, indicative of disease modification. Here, we review the evidence supporting AMPK as a novel pain target pointing out opportunities for further discovery that are likely to have an impact on drug discovery efforts centered around potent and specific allosteric activators of AMPK for chronic pain treatment.