COX inhibitors and bone: A safer impact on osteoblasts by NO-releasing NSAIDs

Identifying alkaline phosphatase inhibitory potential of cyclooxygenase-2 inhibitors: Insights from molecular docking, MD simulations, molecular expression analysis in MCF-7 breast cancer cell line and in vitro investigations

Alkaline phosphatases (APs, EC 3.1.3.1) belong to a superfamily of biological macromolecules that dephosphorylate many phosphometabolites and phosphoproteins and their overexpression is intricated in the spread of cancer to liver and bones, neuronal disorders including Alzheimer's disease (AD), inflammation and others. It was hypothesized that cyclooxygenase-2 (COX-2) selective inhibitors may possess anti-APs potential and may be involved in anticancer proceedings. Three COX-2 inhibitors including nimesulide, piroxicam and lornoxicam were evaluated for the inhibition of APs using in silico and in vitro methods. Molecular docking studies against tissue nonspecific alkaline phosphatase (TNAP) offered the best binding affinities for nimesulide (-11.14 kcal/mol) supported with conventional hydrogen bonding and hydrophobic interactions. MD simulations against TNAP for 200 ns and principal component analysis (PCA) reiterated the stability of ligand-receptor complexes. Molecular expression analysis of TNAP enzyme in the breast cancer cell line MCF-7 exhibited 0.24-fold downregulation with 5 μM nimesulide as compared with 0.26-fold standard 10 μM levamisole. In vitro assays against human placental AP (hPAP) displayed potent inhibitions of these drugs with IC50 values of 0.52 ± 0.02 μM to 3.46 ± 0.13 μM and similar results were obtained for bovine intestinal AP (bIAP). The data when generalized collectively emphasizes that the inhibition of APs by COX-2 inhibitors provides another target to work on the development of anticancer drugs.

Decoding the Structural Diversity: A New Horizon in Antimicrobial Prospecting and Mechanistic Investigation

The escalating crisis of antimicrobial resistance (AMR) underscores the urgent need for novel antimicrobials. One promising strategy is the exploration of structural diversity, as diverse structures can lead to diverse biological activities and mechanisms of action. This review delves into the role of structural diversity in antimicrobial discovery, highlighting its influence on factors such as target selectivity, binding affinity, pharmacokinetic properties, and the ability to overcome resistance mechanisms. We discuss various approaches for exploring structural diversity, including combinatorial chemistry, diversity-oriented synthesis, and natural product screening, and provide an overview of the common mechanisms of action of antimicrobials. We also describe techniques for investigating these mechanisms, such as genomics, proteomics, and structural biology. Despite significant progress, several challenges remain, including the synthesis of diverse compound libraries, the identification of active compounds, the elucidation of complex mechanisms of action, the emergence of AMR, and the translation of laboratory discoveries to clinical applications. However, emerging trends and technologies, such as artificial intelligence, high-throughput screening, next-generation sequencing, and open-source drug discovery, offer new avenues to overcome these challenges. Looking ahead, we envisage an exciting future for structural diversity-oriented antimicrobial discovery, with opportunities for expanding the chemical space, harnessing the power of nature, deepening our understanding of mechanisms of action, and moving toward personalized medicine and collaborative drug discovery. As we face the continued challenge of AMR, the exploration of structural diversity will be crucial in our search for new and effective antimicrobials.

Carbon Monoxide and Nitric Oxide as Examples of the Youngest Class of Transmitters

The year 2021 is the 100th anniversary of the confirmation of the neurotransmission phenomenon by Otto Loewi. Over the course of the hundred years, about 100 neurotransmitters belonging to many chemical groups have been discovered. In order to celebrate the 100th anniversary of the confirmation of neurotransmitters, we present an overview of the first two endogenous gaseous transmitters i.e., nitric oxide, and carbon monoxide, which are often termed as gasotransmitters.

Orally Administered NSAIDs-General Characteristics and Usage in the Treatment of Temporomandibular Joint Osteoarthritis-A Narrative Review

Background: Temporomandibular joint osteoarthritis (TMJ OA) is a degenerative joint disease. The aim of this review was to present the general characteristics of orally administered nonsteroidal anti-inflammatory drugs (NSAIDs) and to present the efficacy of NSAIDs in the treatment of TMJ OA. Methods: PubMed database was analyzed with the keywords: "(temporomandibular joint) AND ((disorders) OR (osteoarthritis) AND (treatment)) AND (nonsteroidal anti-inflammatory drug)". After screening of 180 results, 6 studies have been included in this narrative review. Results and Conclusions: Nonsteroidal anti-inflammatory drugs are one of the most commonly used drugs for alleviation of pain localized in the orofacial area. The majority of articles predominantly examined and described diclofenac sodium in the treatment of pain in the course of TMJ OA. Because of the limited number of randomized studies evaluating the efficacy of NSAIDs in the treatment of TMJ OA, as well as high heterogeneity of published researches, it seems impossible to draw up unequivocal recommendations for the usage of NSAIDs in the treatment of TMJ OA. However, it is highly recommended to use the lowest effective dose of NSAIDs for the shortest possible time. Moreover, in patients with increased risk of gastrointestinal complications, supplementary gastroprotective agents should be prescribed.

Emerging evidence that adaptive bone formation inhibition by non-steroidal anti-inflammatory drugs increases stress fracture risk

There is mounting evidence suggesting that the commonly used analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), may inhibit new bone formation with physical training and increase risk of stress fractures in physically active populations. Stress fractures are thought to occur when bones are subjected to repetitive mechanical loading, which can lead to a cycle of tissue microdamage, repair, and continued mechanical loading until fracture. Adaptive bone formation, particularly on the periosteal surface of long bones, is a concurrent adaptive response of bone to heightened mechanical loading that can improve the fatigue resistance of the skeletal structure, and therefore may play a critical role in offsetting the risk of stress fracture. Reports from animal studies suggest that NSAID administration may suppress this important adaptive response to mechanical loading. These observations have implications for populations such as endurance athletes and military recruits who are at risk of stress fracture and whose use of NSAIDs is widespread. However, results from human trials evaluating exercise and bone adaptation with NSAID consumption have been less conclusive. In this review, we identify knowledge gaps that must be addressed to further support NSAID-related guidelines intended for at-risk populations and individuals.

Etoricoxib decreases subchondral bone mass and attenuates biomechanical properties at the early stage of osteoarthritis in a mouse model

Etoricoxib, a selective Cyclooxygenase-2 (COX-2) inhibitor, is commonly used in osteoarthritis (OA) for pain relief, however, little is known about the effects on subchondral bone. In the current study, OA was induced via destabilization of the medial meniscus (DMM) in C57BL/6 mice. Two days after surgery, mice were treated with different concentrations of Etoricoxib. Four weeks after treatment, micro computed tomography (Micro-CT) analysis, histological analysis, atomic force microscopy (AFM) analysis, and scanning electron microscopy (SEM) were performed to evaluate OA progression. We demonstrated that Etoricoxib inhibited osteophyte formation in the subchondral bone. However, it also reduced the bone volume fraction (BV/TV), lowered trabecular thickness (Tb.Th), and more microfractures and pores were observed in the subchondral bone. Moreover, Etoricoxib reduced the elastic modulus of subchondral bone. Exposure to Etoricoxib further increased the empty/total osteocyte ratio of the subchondral bone. Etoricoxib did not show significant improvement in articular cartilage destruction and synovial inflammation in early OA. Together, our observations suggested that although Etoricoxib can relieve OA-induced pain and inhibit osteophyte formation in the subchondral bone, it can also change the microstructures and biomechanical properties of subchondral bone, promote subchondral bone loss, and reduce subchondral bone quality in early OA mice.

The role of autonomously secreted PGE2 and its autocrine/paracrine effect on bone matrix mineralization at the different stages of differentiating MC3T3-E1 cells

Bone is consisted of osteoblast-linage cells, bone-forming cells in various differentiation stages. However, it is not fully understood how communicate and interact these cells immigrated from bone marrow. In this study, we showed that prostaglandin E2 (PGE₂) had a role in autonomous modification of matrix mineralization in osteoblastic cell line, MC3T3-E1, and interactions across the cells in different differentiation stages. Analysis using LC-MS/MS and inhibitors showed the autonomous secretion of PGE₂ among the prostanoids in differentiation stages and that depend on COX-2, a key enzyme for production of PGE₂. Treatment with inhibitors of PGE₂ receptors and COX-2 indicated that secreted PGE₂ regulates matrix mineralization in an autocrine/paracrine manner. In addition, we showed that the expression profile of PGE₂ receptors (EP1-EP4) and PGE₂ effects on matrix mineralization derived from it changed during cell differentiation. Treatment with inhibitors of PGE₂ signaling in the early differentiation stage of MC3T3-E1 cells induced significant changes in matrix mineralization several days after. Stimulation with the extracts from culture medium of the matured cells including PGE₂ and co-culture with the matured cells secreting PGE₂ significantly promoted matrix mineralization of the early stage cells, in contrast, treatment with inhibitor of COX-2 and PGE₂ receptors failed to do so. These results support that PGE₂ plays important roles in the interaction system of osteoblast-linage cells in bone tissue to regulate matrix mineralization reflecting condition of bone-forming cells, that is, population and maturation.

Valve Interstitial Cell-Specific Cyclooxygenase-1 Associated With Calcification of Aortic Valves

BACKGROUND

The molecular mechanisms underlying aortic valve calcification are poorly understood. Here, we aimed to identify the master regulators of calcification by comparison of genes in valve interstitial cells (VICs) with calcified and noncalcified aortic valves.

METHODS

Calcified aortic valves were surgically excised from patients with aortic valve stenosis who required aortic valve replacements. Noncalcified and calcified sections were obtained from aortic valve leaflets. Collagenase-digested tissues were seeded into dishes, and VICs adhering to the dishes were cultured for 3 weeks, followed by comprehensive gene expression analysis. Functional analyses of identified proteins were performed by in vitro calcification assays. Tissue localization was determined by immunohistochemical staining for normal (n = 11) and stenotic valves (n = 30).

RESULTS

We found 87 genes showing greater than a twofold change in calcified tissues. Among these genes, 68 were downregulated and 19 were upregulated. Cyclooxygenase-1 (COX1) messenger RNA and protein levels were upregulated in VICs from calcified tissues. The COX1 messenger RNA and protein levels in VICs were also strongly increased by stimulation with osteoblast differentiation medium. These were VIC-specific phenotypes and were not observed in other cell types. Immunohistochemical staining revealed that COX1-positive VICs were specifically localized in the calcified area of aortic valve tissues.

CONCLUSIONS

The VIC-specific COX1 overexpression played a crucial role in calcification by promoting osteoblast differentiation in aortic valve tissues.

Regulation of MC3T3-E1 differentiation by actin cytoskeleton through lipid mediators reflecting the cell differentiation stage

Actin cytoskeleton is reported to be related in various functions of osteoblast, bone-forming cell. However the function of actin cytoskeleton in osteoblasts is not fully understood, since bone formation is derived from extracellular interactions of functional proteins produced from osteoblasts, including osteocalcin (Ocn), and it is a result of closely and complex organized sequence of biochemical events. In this study, we showed that actin cytoskeleton of MC3T3-E1 cells functioned in recognition of cell condition and regulation of extracellular matrix mineralization, bone formation. Maturation of MC3T3-E1 cells by 14 days of culture reduced F-actin filaments, while induced expression of Ocn mRNA known as late stage differentiation marker and matrix mineralization, terminal stage of cell differentiation. The disruption of actin cytoskeleton with Cyto D in immature MC3T3-E1 cells significantly increased expression of Ocn mRNA in 24 h. Both PTX-induced inhibition of signal transduction through GPCRs and celecoxib-induced suppression of lipid mediators in immature MC3T3-E1 cells reduced actin filaments and suppressed matrix mineralization. Furthermore, addition of lipid mediators extracted from culture mediums of differentiated MC3T3-E1 cells by Bligh-Dyer method induced actin cytoskeleton reorganization and matrix mineralization change in MC3T3-E1 cells. Taken together, our data suggest that actin cytoskeleton of MC3T3-E1 cells regulates activation of developmental pathway reflecting cell differentiation stages through lipid mediators. The function we identified is important for bone formation tightly regulated by mechanical stress, since actin cytoskeleton is also known as a mechanosensor of osteoblasts.