Piperine, an alkaloid inhibiting the super-relaxed state of myosin, binds to the myosin regulatory light chain

Piperine enhances contractile force in slow- and fast-twitch muscle

Piperine has been shown to bind to myosin and shift the distribution of conformational states of myosin molecules from the super-relaxed state to the disordered relaxed state. However, little is known about the implications for muscle force production and potential underlying mechanisms. Muscle contractility experiments were performed using isolated muscles and single fibres from rats and mice. The dose-response effect of piperine on muscle force was assessed at several stimulation frequencies. The potentiation of muscle force was also tested in muscles fatigued by eccentric contractions. Potential mechanisms of force potentiation were assessed by measuring Ca2+ levels during stimulation in enzymatically dissociated muscle fibres, while myofibrillar Ca2+ sensitivity was assessed in chemically skinned muscle fibres. Piperine caused a dose-dependent increase in low-frequency force with no effect on high-frequency force in both slow- and fast-twitch muscle, with similar relative increases in twitch force, rate of force development and relaxation rate. The potentiating effect of piperine on low-frequency force was reversible, and piperine partially recovered low-frequency force in fatigued muscle. Piperine had no effect on myoplasmic free [Ca2+] levels in mouse muscle fibres, whereas piperine substantially augmented the force response to submaximal levels of [Ca2+] in rat MyHCII fibres and MyHCI fibres along with a minor increase in maximum Ca2+-activated force. Piperine enhances low-frequency force production in both fast- and slow-twitch muscle. The effects are reversible and can counteract muscle fatigue. The primary underlying mechanism appears to be an increase in Ca2+ sensitivity. KEY POINTS: Piperine is a plant alkaloid derived from black pepper. It is known to bind to skeletal muscle myosin and enhance resting ATP turnover but its effects on contractility are not well known. We showed for the first time a piperine-induced force potentiation that was pronounced during low-frequency electrical stimulation of isolated muscles. The effect of piperine was observed in both slow and fast muscle types, was reversible, and could counteract the force decrements observed after fatiguing muscle contractions. Piperine treatment caused an increase in myofibrillar Ca2+ sensitivity in chemically skinned muscle fibres, while we observed no effect on intracellular Ca2+ concentrations during electrical stimulation in enzymatically dissociated muscle fibres.

Extraction, Characterization, and Evaluation of the Cytotoxic Activity of Piperine in Its Isolated form and in Combination with Chemotherapeutics against Gastric Cancer

Gastric cancer is one of the most frequent types of neoplasms worldwide, usually presenting as aggressive and difficult-to-manage tumors. The search for new structures with anticancer potential encompasses a vast research field in which natural products arise as promising alternatives. In this scenario, piperine, an alkaloid of the Piper species, has received attention due to its biological activity, including anticancer attributes. The present work proposes three heating-independent, reliable, low-cost, and selective methods for obtaining piperine from Piper nigrum L. (Black pepper). Electronic (SEM) and optical microscopies, X-ray diffraction, nuclear magnetic resonance spectroscopies (¹³C and ¹H NMR), and optical spectroscopies (UV-Vis, photoluminescence, and FTIR) confirm the obtention of piperine crystals. The MTT assay reveals that the piperine samples exhibit good cytotoxic activity against primary and metastasis models of gastric cancer cell lines from the Brazilian Amazon. The samples showed selective cytotoxicity on the evaluated models, revealing higher effectiveness in cells bearing a higher degree of aggressiveness. Moreover, the investigated piperine crystals demonstrated the ability to act as a good cytotoxicity enhancer when combined with traditional chemotherapeutics (5-FU and GEM), allowing the drugs to achieve the same cytotoxic effect in cells employing lower concentrations. These results establish piperine as a promising molecule for therapy investigations in aggressive gastric cancer, both in its isolated form or as a bioenhancer.

Piperine ameliorates psoriatic skin inflammation by inhibiting the phosphorylation of STAT3

Psoriasis is a common chronic inflammatory skin disease that is easy to relapse and difficult to cure. Piperine is the main alkaloid extracted from black pepper, and its role in psoriasis has not been previously reported. We identified that piperine ameliorated M5-induced psoriatic skin lesions. Furthermore, piperine alleviated psoriasis pathological features including epidermal hyperplasia and inflammatory cell infiltration, decreased the expression of psoriasis-characteristic cytokines, chemokines and proteins in IMQ-induced psoriasiform dermatitis. Moreover, we determined that piperine inhibited the phosphorylation of STAT3 in M5- and IMQ-induced psoriasis-like skin lesions. Our data demonstrated that piperine ameliorated psoriatic skin inflammation by inhibiting the phosphorylation of STAT3. Therefore, piperine may be one potential compound candidate for psoriasis therapy, providing new strategies for clinical intervention.

The influence of piperine on oxidation-induced porcine myofibrillar protein gelation behavior and fluorescent advanced glycation end products formation in model systems

This study investigated the effects of piperine on oxidation-induced porcine myofibrillar protein (MP) gelation behavior and fluorescent advanced glycation end products (fAGEs) formation. Model systems were prepared, lipid oxidation, MP gelling behavior, and fAGEs content were determined daily. The results indicated that lipid oxidation, carbonyl content, S₀, cooking loss, and tryptophan fluorescence intensity of MP significantly decreased, whereas gel strength, WHC, and whiteness markedly increased as the concentration of piperine increased (from 0 to 30 μM/g protein), indicating that piperine could reduce lipid oxidation and oxidative damage to MP. The fluorescence intensity of fAGEs markedly decreased (P < 0.05), from 93.1 ± 4.4 to 61.2 ± 3.0, as the concentration of piperine increased from 0 μM/g protein to 30 μM/g protein after 5 days of incubation. These results in model systems suggest that the presence of piperine has an important role in the inhibition of MP oxidation and fAGEs formation.

Myosin Heavy Chain as a Novel Key Modulator of Striated Muscle Resting State

After years of intense research using structural, biological, and biochemical experimental procedures, it is clear that myosin molecules are essential for striated muscle contraction. However, this is just the tip of the iceberg of their function. Interestingly, it has been shown recently that these molecules (especially myosin heavy chains) are also crucial for cardiac and skeletal muscle resting state. In the present review, we first overview myosin heavy chain biochemical states and how they influence the consumption of ATP. We then detail how neighboring partner proteins including myosin light chains and myosin binding protein C intervene in such processes, modulating the ATP demand in health and disease. Finally, we present current experimental drugs targeting myosin ATP consumption and how they can treat muscle diseases.

NEB mutations disrupt the super-relaxed state of myosin and remodel the muscle metabolic proteome in nemaline myopathy

Nemaline myopathy (NM) is one of the most common non-dystrophic genetic muscle disorders. NM is often associated with mutations in the NEB gene. Even though the exact NEB-NM pathophysiological mechanisms remain unclear, histological analyses of patients' muscle biopsies often reveal unexplained accumulation of glycogen and abnormally shaped mitochondria. Hence, the aim of the present study was to define the exact molecular and cellular cascade of events that would lead to potential changes in muscle energetics in NEB-NM. For that, we applied a wide range of biophysical and cell biology assays on skeletal muscle fibres from NM patients as well as untargeted proteomics analyses on isolated myofibres from a muscle-specific nebulin-deficient mouse model. Unexpectedly, we found that the myosin stabilizing conformational state, known as super-relaxed state, was significantly impaired, inducing an increase in the energy (ATP) consumption of resting muscle fibres from NEB-NM patients when compared with controls or with other forms of genetic/rare, acquired NM. This destabilization of the myosin super-relaxed state had dynamic consequences as we observed a remodeling of the metabolic proteome in muscle fibres from nebulin-deficient mice. Altogether, our findings explain some of the hitherto obscure hallmarks of NM, including the appearance of abnormal energy proteins and suggest potential beneficial effects of drugs targeting myosin activity/conformations for NEB-NM.

Analysis methods and quality criteria for investigating muscle physiology using x-ray diffraction

X-ray diffraction studies of muscle have been tremendously powerful in providing fundamental insights into the structures of, for example, the myosin and actin filaments in a variety of muscles and the physiology of the cross-bridge mechanism during the contractile cycle. However, interpretation of x-ray diffraction patterns is far from trivial, and if modeling of the observed diffraction intensities is required it needs to be performed carefully with full knowledge of the possible pitfalls. Here, we discuss (1) how x-ray diffraction can be used as a tool to monitor various specific muscle properties and (2) how to get the most out of the rest of the observed muscle x-ray diffraction patterns by modeling where the reliability of the modeling conclusions can be objectively tested. In other x-ray diffraction methods, such as protein crystallography, the reliability of every step of the process is estimated and quoted in published papers. In this way, the quality of the structure determination can be properly assessed. To be honest with ourselves in the muscle field, we need to do as near to the same as we can, within the limitations of the techniques that we are using. We discuss how this can be done. We also use test cases to reveal the dos and don’ts of using x-ray diffraction to study muscle physiology.

To lie or not to lie: Super-relaxing with myosins

Since the discovery of muscle in the 19th century, myosins as molecular motors have been extensively studied. However, in the last decade, a new functional super-relaxed (SRX) state of myosin has been discovered, which has a 10-fold slower ATP turnover rate than the already-known non-actin-bound, disordered relaxed (DRX) state. These two states are in dynamic equilibrium under resting muscle conditions and are thought to be significant contributors to adaptive thermogenesis in skeletal muscle and can act as a reserve pool that may be recruited when there is a sustained demand for increased cardiac muscle power. This report provides an evolutionary perspective of how striated muscle contraction is regulated by modulating this myosin DRX↔SRX state equilibrium. We further discuss this equilibrium with respect to different physiological and pathophysiological perturbations, including insults causing hypertrophic cardiomyopathy, and small-molecule effectors that modulate muscle contractility in diseased pathology.

A plant-mediated synthesis of nanostructured hydroxyapatite for biomedical applications: a review

The engineering of calcium-based phosphate materials at the nanoscale gains several unique properties compared to the bulky state. The effort to scale down, e.g., from bulky state to nanoscale in order to control the morphology and improve structural properties requires the use of varying reagents that can be detrimental to the environment. A typical example of these materials is hydroxyapatite (HAp), one of the well-known calcium phosphate materials, which has a close resemblance to human bone tissue. HAp has valuable applications in catalysis, drug delivery, bone and dental implant formation, and adsorption. Hydroxyapatite-based nanomaterials synthesized through conventional routes make use of reagents that are not environmental friendly and are very costly. Since the current research trends are geared towards producing/synthesizing nanomaterials through an eco-friendly approach, there is the need to consider the techniques and reagents involved in the synthesis of HAp. This review touches on the possible replacement of such synthetic chemical reagents, synthesis routes, and toxic capping agents with plant extracts for synthesizing HAp-based nanomaterials for multi-functional applications. The influence of biomolecules from plants on synthesized HAps and the attainable mechanism during these green approaches are discussed. Viable future modifications of the methods used to obtain extracts from plants are also studied.