The role of NLRP3 inflammasome in inflammation-related skeletal muscle atrophy

Critical illness-associated limb and diaphragmatic weakness

PURPOSE OF REVIEW

In the current review, we aim to highlight the evolving evidence on the diagnosis, prevention and treatment of critical illness weakness (CIW) and critical illness associated diaphragmatic weakness (CIDW).

RECENT FINDINGS

In the ICU, several risk factors can lead to CIW and CIDW. Recent evidence suggests that they have different pathophysiological mechanisms and impact on outcomes, although they share common risk factors and may overlap in several patients. Their diagnosis is challenging, because CIW diagnosis is primarily clinical and, therefore, difficult to obtain in the ICU population, and CIDW diagnosis is complex and not easily performed at the bedside. All of these issues lead to underdiagnosis of CIW and CIDW, which significantly increases the risk of complications and the impact on both short and long term outcomes. Moreover, recent studies have explored promising diagnostic techniques that are may be easily implemented in daily clinical practice. In addition, this review summarizes the latest research aimed at improving how to prevent and treat CIW and CIDW.

SUMMARY

This review aims to clarify some uncertain aspects and provide helpful information on developing monitoring techniques and therapeutic interventions for managing CIW and CIDW.

Exploring ncRNA-mediated pathways in sepsis-induced pyroptosis

Sepsis, a potentially fatal illness caused by an improper host response to infection, remains a serious problem in the world of healthcare. In recent years, the role of ncRNA has emerged as a pivotal aspect in the intricate landscape of cellular regulation. The exploration of ncRNA-mediated regulatory networks reveals their profound influence on key molecular pathways orchestrating pyroptotic responses during septic conditions. Through a comprehensive analysis of current literature, we navigate the diverse classes of ncRNAs, including miRNAs, lncRNAs, and circRNAs, elucidating their roles as both facilitators and inhibitors in the modulation of pyroptotic processes. Furthermore, we highlight the potential diagnostic and therapeutic implications of targeting these ncRNAs in the context of sepsis, aiming to cover the method for novel and effective strategies to mitigate the devastating consequences of septic pathogenesis. As we unravel the complexities of this regulatory axis, a deeper understanding of the intricate crosstalk between ncRNAs and pyroptosis emerges, offering promising avenues for advancing our approach to sepsis intervention. The intricate pathophysiology of sepsis is examined in this review, which explores the dynamic interaction between ncRNAs and pyroptosis, a highly regulated kind of programmed cell death.

The possible mechanisms of ferroptosis in sepsis-associated acquired weakness

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, and its morbidity and mortality rates are increasing annually. It is an independent risk factor for intensive care unit-acquired weakness (ICU-AW), which is a common complication of patients in ICU. This situation is also known as sepsis-associated acquired weakness (SAW), and it can be a complication in more than 60% of patients with sepsis. The outcomes of SAW are often prolonged mechanical ventilation, extended hospital stays, and increased morbidity and mortality of patients in ICUs. The pathogenesis of SAW is unclear, and an effective clinical treatment is not available. Ferroptosis is an iron-dependent type of cell death with unique morphological, biochemical, and genetic features. Unlike other forms of cell death such as autophagy, apoptosis, and necrosis, ferroptosis is primarily driven by lipid peroxidation. Cells undergo ferroptosis during sepsis, which further enhances the inflammatory response. This process leads to increased cell death, as well as multi-organ dysfunction and failure. Recently, there have been sporadic reports suggesting that SAW is associated with ferroptosis, but the exact pathophysiological mechanisms remain unclear. Therefore, we reviewed the possible pathogenesis of ferroptosis that leads to SAW and offer new strategies to prevent and treat SAW.

MCC950 Ameliorates Diabetic Muscle Atrophy in Mice by Inhibition of Pyroptosis and Its Synergistic Effect with Aerobic Exercise

Diabetic muscle atrophy is an inflammation-related complication of type-2 diabetes mellitus (T2DM). Even though regular exercise prevents further deterioration of atrophic status, there is no effective mediator available for treatment and the underlying cellular mechanisms are less explored. In this study, we investigated the therapeutic potential of MCC950, a specific, small-molecule inhibitor of NLRP3, to treat pyroptosis and diabetic muscle atrophy in mice. Furthermore, we used MCC950 to intervene in the protective effects of aerobic exercise against muscle atrophy in diabetic mice. Blood and gastrocnemius muscle (GAS) samples were collected after 12 weeks of intervention and the atrophic state was assessed. We initially corroborated a diabetic muscle atrophy phenotype in db/db mice (D) by comparison with control m/m mice (W) by examining parameters such as fasting blood glucose (D vs. W: 24.47 ± 0.45 mmol L-1 vs. 4.26 ± 0.6 mmol L-1, p < 0.05), grip strength (D vs. W: 166.87 ± 15.19 g vs. 191.76 ± 14.13 g, p < 0.05), exercise time (D vs. W: 1082.38 ± 104.67 s vs. 1716 ± 168.55 s, p < 0.05) and exercise speed to exhaustion (D vs. W: 24.25 ± 2.12 m min-1 vs. 34.75 ± 2.66 m min-1, p < 0.05), GAS wet weight (D vs. W: 0.07 ± 0.01 g vs. 0.13 ± 0.01 g, p < 0.05), the ratio of GAS wet weight to body weight (D vs. W: 0.18 ± 0.01% vs. 0.54 ± 0.02%, p < 0.05), and muscle fiber cross-sectional area (FCSA) (D vs. W: 1875 ± 368.19 µm2 vs. 2747.83 ± 406.44 µm2, p < 0.05). We found that both MCC950 (10 mg kg-1) treatment and exercise improved the atrophic parameters that had deteriorated in the db/db mice, inhibited serum inflammatory markers and significantly attenuated pyroptosis in atrophic GAS. In addition, a combined MCC950 treatment with exercise (DEI) exhibited a further improvement in glucose uptake capacity and muscle performance. This combined treatment also improved the FCSA of GAS muscle indicated by Laminin immunofluorescence compared to the group with the inhibitor treatment alone (DI) (DEI vs. DI: 2597 ± 310.97 vs. 1974.67 ± 326.15 µm2, p < 0.05) or exercise only (DE) (DEI vs. DE: 2597 ± 310.97 vs. 2006.33 ± 263.468 µm2, p < 0.05). Intriguingly, the combination of MCC950 treatment and exercise significantly reduced NLRP3-mediated inflammatory factors such as cleaved-Caspase-1, GSDMD-N and prevented apoptosis and pyroptosis in atrophic GAS. These findings for the first time demonstrate that targeting NLRP3-mediated pyroptosis with MCC950 improves diabetic muscle homeostasis and muscle function. We also report that inhibiting pyroptosis by MCC950 can enhance the beneficial effects of aerobic exercise on diabetic muscle atrophy. Since T2DM and muscle atrophy are age-related diseases, the young mice used in the current study do not seem to fully reflect the characteristics of diabetic muscle atrophy. Considering the fragile nature of db/db mice and for the complete implementation of the exercise intervention, we used relatively young db/db mice and the atrophic state in the mice was thoroughly confirmed. Taken together, the current study comprehensively investigated the therapeutic effect of NLRP3-mediated pyroptosis inhibited by MCC950 on diabetic muscle mass, strength and exercise performance, as well as the synergistic effects of MCC950 and exercise intervention, therefore providing a novel strategy for the treatment of the disease.

The Immunomodulatory Effects of Sulforaphane in Exercise-Induced Inflammation and Oxidative Stress: A Prospective Nutraceutical

Sulforaphane (SFN) is a promising molecule for developing phytopharmaceuticals due to its potential antioxidative and anti-inflammatory effects. A plethora of research conducted in vivo and in vitro reported the beneficial effects of SFN intervention and the underlying cellular mechanisms. Since SFN is a newly identified nutraceutical in sports nutrition, only some human studies have been conducted to reflect the effects of SFN intervention in exercise-induced inflammation and oxidative stress. In this review, we briefly discussed the effects of SFN on exercise-induced inflammation and oxidative stress. We discussed human and animal studies that are related to exercise intervention and mentioned the underlying cellular signaling mechanisms. Since SFN could be used as a potential therapeutic agent, we mentioned briefly its synergistic attributes with other potential nutraceuticals that are associated with acute and chronic inflammatory conditions. Given its health-promoting effects, SFN could be a prospective nutraceutical at the forefront of sports nutrition.

NLRP3 Contributes to Sarcopenia Associated to Dependency Recapitulating Inflammatory-Associated Muscle Degeneration

Sarcopenia, a complex and debilitating condition characterized by progressive deterioration of skeletal muscle, is the primary cause of age-associated disability and significantly impacts healthspan in elderly patients. Despite its prevalence among the aging population, the underlying molecular mechanisms are still under investigation. The NLRP3 inflammasome is crucial in the innate immune response and has a significant impact on diseases related to inflammation and aging. Here, we investigated the expression of the NLRP3 inflammasome pathway and pro-inflammatory cytokines in skeletal muscle and peripheral blood of dependent and independent patients who underwent hip surgery. Patients were categorized into independent and dependent individuals based on their Barthel Index. The expression of NLRP3 inflammasome components was significantly upregulated in sarcopenic muscle from dependent patients, accompanied by higher levels of Caspase-1, IL-1β and IL-6. Among older dependent individuals with sarcopenia, there was a significant increase in the MYH3/MYH2 ratio, indicating a transcriptional shift in expression from mature to developmental myosin isoforms. Creatine kinase levels and senescence markers were also higher in dependent patients, altogether resembling dystrophic diseases and indicating muscle degeneration. In summary, we present evidence for the involvement of the NLRP3/ASC/NEK7/Caspase-1 inflammasome pathway with activation of pro-inflammatory SASP in the outcome of sarcopenia in the elderly.

Molecular Foundations of Inflammatory Diseases: Insights into Inflammation and Inflammasomes

Inflammatory diseases are a global health problem affecting millions of people with a wide range of conditions. These diseases, including inflammatory bowel disease (IBD), rheumatoid arthritis (RA), osteoarthritis (OA), gout, and diabetes, impose a significant burden on patients and healthcare systems. A complicated interaction between genetic variables, environmental stimuli, and dysregulated immune responses shows the complex biological foundation of various diseases. This review focuses on the molecular mechanisms underlying inflammatory diseases, including the function of inflammasomes and inflammation. We investigate the impact of environmental and genetic factors on the progression of inflammatory diseases, explore the connection between inflammation and inflammasome activation, and examine the incidence of various inflammatory diseases in relation to inflammasomes.

Heme oxygenase-1: A potential therapeutic target for improving skeletal muscle atrophy

Skeletal muscle atrophy is a common muscle disease that is directly caused by an imbalance in protein synthesis and degradation. At the histological level, it is mainly characterized by a reduction in muscle mass and fiber cross-sectional area (CSA). Patients with skeletal muscle atrophy present with reduced motor ability, easy fatigue, and poor life quality. Heme oxygenase-1 (HO-1) is an inducible enzyme that catalyzes the degradation of heme and has attracted much attention for its anti-oxidation effects. In addition, there is growing evidence that HO-1 plays an important role in anti-inflammatory, anti-apoptosis, pro-angiogenesis, and maintaining skeletal muscle homeostasis, making it a potential therapeutic target for improving skeletal muscle atrophy. Here, we review the pathogenesis of skeletal muscle atrophy, the biology of HO-1 and its regulation, and the biological function of HO-1 in skeletal muscle homeostasis, with a specific focus on the role of HO-1 in skeletal muscle atrophy, aiming to observe the therapeutic potential of HO-1 for skeletal muscle atrophy.

Maladaptive Immune Activation in Age-Related Decline of Muscle Function

Age-related changes in immune competency and inflammation play a role in the decline of physical function. In this review of the conference on Function-Promoting Therapies held in March 2022, we discuss the biology of aging and geroscience with an emphasis on decline in physical function and the role of age-related changes in immune competence and inflammation. More recent studies in skeletal muscle and aging highlighting a crosstalk between skeletal muscle, neuromuscular feedback, and immune cell subsets are also discussed. The value of strategies targeting specific pathways that affect skeletal muscle and more systems-wide approaches that provide benefits in muscle homeostasis with aging are underscored. Goals in clinical trial design and the need for incorporating differences in life history when interpreting results from these intervention strategies are important. Where applicable, references are made to papers presented at the conference. We conclude by underscoring the need to incorporate age-related immune competency and inflammation when interpreting results from interventions that target specific pathways predicted to promote skeletal muscle function and tissue homeostasis.

Gut microbiota disturbances and protein-energy wasting in chronic kidney disease: a narrative review

Protein-energy wasting (PEW) is common in patients with chronic kidney disease (CKD) and is associated with increased morbidity and mortality, and lower quality of life. It is a complex syndrome, in which inflammation and retention of uremic toxins are two main factors. Causes of inflammation and uremic toxin retention in CKD are multiple; however, gut dysbiosis plays an important role, serving as a link between those entities and PEW. Besides, there are several pathways by which microbiota may influence PEW, e.g., through effects on appetite mediated by microbiota-derived proteins and hormonal changes, or by impacting skeletal muscle via a gut-muscle axis. Hence, microbiota disturbances may influence PEW independently of its relationship with local and systemic inflammation. A better understanding of the complex interrelationships between microbiota and the host may help to explain how changes in the gut affect distant organs and systems of the body and could potentially lead to the development of new strategies targeting the microbiota to improve nutrition and clinical outcomes in CKD patients. In this review, we describe possible interactions of gut microbiota with nutrient metabolism, energy balance, hunger/satiety signals and muscle depletion, all of which are strongly related to PEW in CKD patients.

Inhibition of PFKFB Preserves Intestinal Barrier Function in Sepsis by Inhibiting NLRP3/GSDMD

Intestinal barrier dysfunction is associated with the occurrence and development of sepsis. Further, aerobic glycolysis plays an essential role in inflammation and cell death. This study is aimed at investigating the protective effect and mechanism of PFKFB3 inhibition on intestinal barrier dysfunction in sepsis mice. Sepsis mouse models were established by cecal ligation and puncture (CLP) in wild-type mice and Gsdmd^-/- mice. The results showed that the expression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) in the small intestines was significantly upregulated in sepsis. 3-(3-Pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO), the specific inhibitor of PFKFB3, and Gsdmd gene knockout significantly inhibited the inflammatory response and cell death caused by sepsis, thus alleviating intestinal damage and barrier dysfunction. 3PO was also shown to significantly inhibit oxidative stress and NLRP3/caspase-1/GSDMD-dependent cell pyroptosis in the small intestines. The in vitro studies revealed that 3PO reduced NLRP3/caspase-1/GSDMD-dependent cell pyroptosis by inhibiting ROS. Taken together, our results suggest that PFKFB3 is involved in inflammation, oxidative stress, and pyroptosis during sepsis and enhances intestinal damage, which may provide important clues about the potential targets to be exploited in this highly lethal disease.