Differential expression of Cathepsin S and X in the spinal cord of a rat neuropathic pain model

Metabolic Dysregulation and Its Role in Postoperative Pain among Knee Osteoarthritis Patients

Knee osteoarthritis (KOA) is characterized by low-grade inflammation, loss of articular cartilage, subchondral bone remodeling, synovitis, osteophyte formation, and pain. Strong, continuous pain may indicate the need for joint replacement in patients with end-stage OA, although postoperative pain (POP) of at least a two-month duration persists in 10-40% of patients with OA.

STUDY PURPOSE

The inflammation observed in joint tissues is linked to pain caused by the production of proinflammatory cytokines. Since the biosynthesis of cytokines requires energy, their production is supported by extensive metabolic conversions of carbohydrates and fatty acids, which could lead to a disruption in cellular homeostasis. Therefore, this study aimed to investigate the association between POP development and disturbances in energy metabolic conversions, focusing on carbohydrate and fatty acid metabolism.

METHODS

Peripheral blood samples were collected from 26 healthy subjects and 50 patients with end-stage OA before joint replacement surgery. All implants were validated by orthopedic surgeons, and patients with OA demonstrated no inherent abnormalities to cause pain from other reasons than OA disease, such as malalignment, aseptic loosening, or excessive bleeding. Pain levels were assessed before surgery using the visual analogue scale (VAS) and neuropathic pain questionnaires, DN4 and PainDETECT. Functional activity was evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Three and six months after surgery, pain indices according to a VAS of 30 mm or higher were considered. Total RNA isolated from whole blood was analyzed using quantitative real-time RT-PCR (qRT-PCR) for the expression of genes related to carbohydrate and fatty acid metabolism. Protein levels of the examined genes were measured using an ELISA in the peripheral blood mononuclear cells (PBMCs). We used qRT-PCR because it is the most sensitive and reliable method for gene expression analysis, while an ELISA was used to confirm our qRT-PCR results.

KEY FINDINGS

Among the study cohort, 17 patients who reported POP demonstrated significantly higher (p < 0.05) expressions of the genes PKM2, LDH, SDH, UCP2, CPT1A, and ACLY compared to pain-free patients with KOA. Receiver-operating characteristic (ROC) curve analyses confirmed the association between these gene expressions and pain development post-arthroplasty. A principle component analysis identified the prognostic values of ACLY, CPT1A, AMPK, SDHB, Caspase 3, and IL-1β gene expressions for POP development in the examined subjects.

CONCLUSION

These findings suggest that the disturbances in energy metabolism, as observed in the PBMCs of patients with end-stage KOA before arthroplasty, may contribute to POP development. An understanding of these metabolic processes could provide insights into the pathogenesis of KOA. Additionally, our findings can be used in a clinical setting to predict POP development in end-stage patients with KOA before arthroplasty.

4-Cyanamido-substituted benzenesulfonamides act as dual carbonic anhydrase and cathepsin inhibitors

A set of novel N-cyano-N-substituted 4-aminobenzenesulfonamide derivatives were synthesized and investigated for their inhibitory activity against four cytosolic carbonic anhydrase (CA, EC 4.2.1.1) isoforms (hCA I, II, VII and XIII) and two cathepsins (S and B). N-alkyl/benzyl-substituted derivatives were revealed to be very potent inhibitors against brain-associated hCA VII, but inactive against both cathepsins. On the other hand, N-acyl-substituted derivatives displayed significant inhibitory activities against cathepsin S, but only moderate to poor inhibitory potency against hCA VII. Both hCA VII and cathepsin S have recently been validated as therapeutic targets in neuropathic pain. This study provided an excellent starting point for further structural optimization of this class of bifunctional compounds to enhance their inhibitory activity and selectivity against hCA VII and cathepsin S and to achieve new compounds with an attractive dual mechanism of action as anti-neuropathic agents.

Microneedle-mediated delivery of Ziconotide-loaded liposomes fused with exosomes for analgesia

Ziconotide (ZIC) is an N-type calcium channel antagonist for treating severe chronic pain that is intolerable, or responds poorly to the administration of other drugs, such as intrathecal morphine and systemic analgesics. As it can only work in the brain and cerebrospinal fluid, intrathecal injection is the only administration route for ZIC. In this study, borneol (BOR)-modified liposomes (LIPs) were fused with exosomes from mesenchymal stem cells (MSCs) and loaded with ZIC to prepare microneedles (MNs) to improve the efficiency of ZIC across the blood-brain barrier. To evaluate local analgesic effects of MNs, the sensitivity of behavioral pain to thermal and mechanical stimuli was tested in animal models of peripheral nerve injury, diabetes-induced neuropathy pain, chemotherapy-induced pain, and ultraviolet-B (UV-B) radiation-induced neurogenic inflammatory pain. BOR-modified LIPs loaded with ZIC were spherical or nearly spherical, with a particle size of about 95 nm and a Zeta potential of -7.8 mV. After fusion with MSC exosomes, the particle sizes of LIPs increased to 175 nm, and their Zeta potential increased to -3.8 mV. The nano-MNs constructed based on BOR-modified LIPs had good mechanical properties and could effectively penetrate the skin to release drugs. The results of analgesic experiments showed that ZIC had a significant analgesic effect in different pain models. In conclusion, the BOR-modified LIP membrane-fused exosome MNs constructed in this study for delivering ZIC provide a safe and effective administration for chronic pain treatment, as well as great potential for clinical application of ZIC.

Role of cathepsin K in the expression of mechanical hypersensitivity following intra-plantar inflammation

Persistent/chronic inflammatory pain involves multiple pathophysiological mechanisms and is far more complex than acute/momentary pain. Current therapeutics for chronic inflammatory pain are often not effective because the etiology responsible for the pain is not addressed by traditional pharmacological treatments. Cathepsin K is a cysteine protease that has mostly been studied in the context of bone and joint disorders. Previous work by others has shown that inhibition of cathepsin K activity reduces osteoarthritis-associated nociception in joints. However, the role of cathepsin K in cutaneous inflammation is understudied. We assessed the effectiveness of genetic deletion or pharmacological inhibition of cathepsin K in male mice on the expression of nocifensive behaviors after formalin injection or mechanical and thermal hypersensitivity after injection of complete Freund’s adjuvant (CFA) into the mouse hind paw. Our data demonstrate that cathepsin K knockout mice (Ctsk^−/−) have a reduction in nocifensive behaviors in the formalin test. In addition, Ctsk^−/− do not develop mechanical hypersensitivity after CFA injection for up to 7 days. Moreover, we found that inhibition of cathepsin K reduced mechanical hypersensitivity after CFA injection and mRNA levels, protein levels, and cathepsin K activity levels were elevated after CFA injection. Based upon our data, cathepsin K is indicated to play a role in the expression of chemically-induced cutaneous hypersensitivity, as Ctsk^−/− mice do not develop mechanical hypersensitivity and show a reduction in nocifensive behaviors. Further research is needed to determine whether attenuating cathepsin K activity may generate a clinically relevant therapeutic.

Application of a Sulfoxonium Ylide Electrophile to Generate Cathepsin X-Selective Activity-Based Probes

Cathepsin X/Z/P is cysteine cathepsin with unique carboxypeptidase activity. Its expression is associated with cancer and neurodegenerative diseases, although its roles during normal physiology are still poorly understood. Advances in our understanding of its function have been hindered by a lack of available tools that can specifically measure the proteolytic activity of cathepsin X. We present a series of activity-based probes that incorporate a sulfoxonium ylide warhead, which exhibit improved specificity for cathepsin X compared to previously reported probes. We apply these probes to detect cathepsin X activity in cell and tissue lysates, in live cells and in vivo, and to localize active cathepsin X in mouse tissues by microscopy. Finally, we utilize an improved method to generate chloromethylketones, necessary intermediates for synthesis of acyloxymethylketones probes, by way of sulfoxonium ylide intermediates. In conclusion, the probes presented in this study will be valuable for investigating cathepsin X pathophysiology.

[there any association of metabolic disturbances with joint destruction and pain?]

Osteoarthritis and type 2 diabetes mellitus represent two the most common chronic diseases. They possess many shared epidemiologic traits, have common risk factors, and embody heterogeneous multifactorial pathologies, which develop due to interaction of genetic an environmental factors. In addition, these diseases are often occurring in the same patient. In spite of the differences in clinical manifestation both diseases have similar disturbances of cellular metabolism, primarily associated with ATP production and utilization. The review discusses molecular mechanisms determining pathophysiological processes associated with glucose and lipid metabolism as well as the means aiming to alleviate the disturbances of energy metabolism as a new a therapeutic approach.

Increased immunoreactivity of cathepsins in the rat esophagus under chronic acid reflux esophagitis

We have designed a stable rat chronic acid reflux esophagitis (RE) model. In gastrointestinal lesions, several lysosomal cathepsins are known to participate in epithelial permeability in cell-cell connections, such as tight junctions in ulcerative colitis. However, very few studies have focused on the distribution of cathepsins in the esophageal multilayer squamous epithelium. Therefore to clarify the role of cathepsins in RE, we investigated their immunohistological localization in the esophageal epithelium under normal conditions and after RE. Of the cathepsins examined (cathepsins B, C, D, F, H, L, S, and X), granular immunoreactivity for cathepsins B, C, D and L was observed in the control esophageal epithelia; although, their distribution differed depending on the enzyme examined. In the RE model, immunoreactivity of these cathepsins was increased in esophageal epithelial cells and activated macrophages. The immunoreactivity for cathepsins F, H, S and X was barely detectable in the control esophageal epithelium. However, in the RE model, we noticed a slight increase in the expression of cathepsins H and X in the epithelial cells. Furthermore, activated macrophages of the RE model possessed intense immunoreactivity for these cathepsins, which may have been related to esophageal inflammatory mechanisms.

Upregulation of cathepsin S in psoriatic keratinocytes

Cathepsin S (CATS) is a cysteine protease, well known for its role in MHC class II-mediated antigen presentation and extracellular matrix degradation. Disturbance of the expression or metabolism of this protease is a concomitant feature of several diseases. Given this importance we studied the localization and regulation of CATS expression in normal and pathological human/mouse skin. In normal human skin CATS-immunostaining is mainly present in the dermis and is localized in macrophages, Langerhans, T- and endothelial cells, but absent in keratinocytes. In all analyzed pathological skin biopsies, i.e. atopic dermatitis, actinic keratosis and psoriasis, CATS staining is strongly increased in the dermis. But only in psoriasis, CATS-immunostaining is also detectable in keratinocytes. We show that cocultivation with T-cells as well as treatment with cytokines can trigger expression and secretion of CATS, which is involved in MHC II processing in keratinocytes. Our data provide first evidence that CATS expression (i) is selectively induced in psoriatic keratinocytes, (ii) is triggered by T-cells and (iii) might be involved in keratinocytic MHC class II expression, the processing of the MHC class II-associated invariant chain and remodeling of the extracellular matrix. This paper expands our knowledge on the important role of keratinocytes in dermatological disease.