Persistent activation of nuclear factor B (NF-κB) is very important in the modulation of macrophages cellular response to microbial infections. The deubiquitinase USP14, which is critical for ubiquitin-mediated proteasomal degradation of proteins, is known to be involved in cancer, neurological diseases, and aging. However, the mechanism by which USP14 regulates inflammation remains unclear. Here, we demonstrated that decreasing the deubiquitinase activity of USP14 resulted in reduced lipopolysaccharides (LPS)-mediated tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 release in THP-1 and RAW264.7 cells. Meanwhile, USP14 knockdown by siRNA showed the same effects, with no cytotoxicity in THP-1 cells. Moreover, inhibiting the deubiquitinase activity of USP14 or USP14 knockdown resulted in decreased ERK1/2 and IκBα phosphorylation, increased amounts of the NF-κB inhibitor IκBα, and reduced NF-κB p65 transport from the cytoplasm into nucleus. These findings suggested that USP14 induces NF-κB activity and ERK1/2 phosphorylation triggered by microbial infection.

Background/Aims: Cardiac hypertrophy is a major outcome and compensatory response of the cardiovascular system to hemodynamic and additional stress responses that ultimately lead to heart failure. Auranofin (Aur) has been used for treating rheumatic arthritis for several decades. Aur is a 19S proteasome-associated deubiquitinase inhibitor, and inhibition of the proteasome is speculated to reverse cardiac hypertrophy. However, the role of the deubiquitinases, especially 19S proteasome-associated deubiquitinases, in the regulation of cardiac remodeling remains poorly understood. The present study investigated the role of Aur in cardiac hypertrophy both in vitro and in vivo. Methods: Male Sprague-Dawley rats underwent abdominal aortic constriction to induce left ventricular hypertrophy. The neonatal rat primary myocardial cell hypertrophy model was induced by Ang II. Echocardiography, hematoxylin-eosin staining, Masson's trichrome staining, immunochemistry, western blot analysis, a cell viability assay, and enzyme-linked immunosorbent assay were performed. Results: Aur significantly reduced the abdominal aortic constriction that led to left ventricular hypertrophy, reduced heart cavity expansion, and functional disorder, and thereby reduced fetal gene expression and attenuated cardiac fibrosis. Furthermore, Aur caused marked accumulation of ubiquitinated proteins and IκBα, as well as inactivation of NF-κB. This phenomenon was confirmed in the neonatal rat primary myocardial cell hypertrophy model. Conclusions: The present study indicated that Aur blocks the development of left ventricular hypertrophy induced by abdominal aortic constriction. This phenomenon might be attributed to inhibition of the 19S proteasome-associated deubiquitinase that can lead to aggregation

Inflammation is a common pathophysiological process as well as a clinical threat that occurs in various diseases worldwide. It is well‐documented that nuclear factor‐κB (NF‐κB) and mitogen‐activated protein kinase pathways are involved in inflammatory reactions to microbial infections in lipopolysaccharide (LPS)‐activated macrophages. The deubiquitinase ubiquitin carboxyl‐terminal hydrolase‐L1 (UCHL1) has been reported as an oncoprotein to promote the growth and progression of cancer cells. However, the regulatory mechanism of UCHL1 in inflammation is currently unclear. Here, we aimed to assess the effects of UCHL1 on LPS‐associated inflammatory response in vitro and in vivo by enzyme‐linked immunosorbent assay, quantitative reverse‐transcription polymerase chain reaction, and western blot analysis. This study identified that inhibition or knockdown of UCHL1 decreased the amounts of the key pro‐inflammatory cytokines, including interleukin‐6 and tumor necrosis factor‐α in macrophages. Additionally, inhibition of UCHL1 suppressed LPS‐induced extracellular signal‑regulated protein kinase 1/2 phosphorylation and NF‐κB translocation by regulating the inhibitor of NF‐κB. Mechanically, UCHL1 interacts with IκBα protein in THP‐1. Meanwhile, inhibition of UCHL1 blocked the LPS‐induced degradation of IκBα through the ubiquitin‐proteasome system. Moreover, in vivo assay showed that suppression of UCHL1 notably reduced the LPS‐induced animal death and release of pro‐inflammatory cytokines. Overall, the current findings uncover that UCHL1 functions as a crucial regulator for inflammatory response via reversing the degradation of IκBα, representing a potential target for the treatment of inflammatory diseases.

b-AP15 is a deubiquitinase (DUB) inhibitor of 19S proteasomes, which in turn targets ubiquitin C-terminal hydrolase 5 (UCHL5) and ubiquitin-specific peptidase 14 (USP14). Nuclear factor kappa B (NF-κB) is closely linked to cellular response in macrophages when the organism is in the state of microbial infection, and it acts as a vital part in the mechanism of inflammatory reaction. However, the molecular mechanism by which DUB inhibitors, especially b-AP15, regulates inflammation remains poorly understood. This study aimed to investigate the relationship between b-AP15 and inflammation. The results showed that b-AP15 treatment significantly reduced the amounts of inflammatory indicators, such as tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) in lipopolysaccharide (LPS)-stimulated THP-1 and macrophages. Meanwhile, similar results were obtained from in vivo experiments. In addition, b-AP15 also significantly improved the survival rate of sepsis mouse via high-density LPS mediation. Furthermore, b-AP15 also inhibited the ERK1/2 and JNK phosphorylation, increased IκBα levels, and inhibited NF-κB p65 by removing them from the cytoplasm into the nucleus. All these findings suggested that b-AP15 has anti-inflammatory action and acts as a potential neoteric target drug for treating microbial infection.

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