Persistent damage to liver cells leads to liver fibrosis, which is characterized by the accumulation of scar tissue in the liver, ultimately leading to cirrhosis and serious complications. Because it is difficult to reverse cirrhosis once it has progressed, the primary focus has been on preventing the progression of liver fibrosis. However, studies on therapeutic agents for liver fibrosis are still lacking. Here, we investigated that the natural dipeptide cyclic histidine-proline (CHP, also known as diketopiperazine) shows promising potential as a therapeutic agent in models of liver injury by inhibiting the progression of fibrosis through activation of the Nrf2 pathway. To elucidate the underlying biological mechanism of CHP, we used the Cellular Thermal Shift Assay (CETSA)-LC-MS/MS, a label-free compound-based target identification platform. Chloride intracellular channel protein 1 (CLIC1) was identified as a target whose thermal stability is increased by CHP treatment. We analyzed the direct interaction of CHP with CLIC1 which revealed a potential interaction between CHP and the E228 residue of CLIC1. Biological validation experiments showed that knockdown of CLIC1 mimicked the antioxidant effect of CHP. Further investigation using a mouse model of CCl₄-induced liver fibrosis in wild-type and CLIC1 KO mice revealed the critical involvement of CLIC1 in mediating the effects of CHP. Taken together, our results provide evidence that CHP exerts its anti-fibrotic effects through specific binding to CLIC1. These insights into the mechanism of action of CHP may pave the way for the development of novel therapeutic strategies for fibrosis-related diseases.

Asthma is a chronic lung disease characterized by airway inflammation, hyperresponsiveness, and narrowing, with a risk of life-threatening attacks. Most current treatments primarily consist of inhalable steroids, which are not without adverse effects. Recently, there has been growing interest in alternative approaches to asthma management. In this study, we investigated the anti-asthmatic effects of the non-steroidal compound CycloZ using acute and chronic mouse models of asthma. Allergic reactions were induced with house dust mite (HDM) extract, and CycloZ or fluticasone propionate (FP) was administered orally or intranasally, respectively. CycloZ significantly ameliorated the HDM-induced robust expression of Th2 cytokines in both models. CycloZ also decreased immune cell infiltration into the lungs and reduced IL-4 and IL-13 cytokine levels in bronchoalveolar lavage fluid (BALF). Moreover, CycloZ greatly attenuated the activation of the TLR-4 pathway, which is involved in HDM recognition and signaling. The beneficial effects of CycloZ were comparable to or even superior to the current steroid treatment, FP, suggesting that CycloZ could be a promising new option for asthma therapy.

Amino acids are key regulators of metabolism, their coordinated effects on skeletal muscle signaling and metabolic remodeling under physiological conditions remain incompletely understood. Here, we investigated whether 14 weeks of combined histidine and proline supplementation (HISPRO; 700 mg/kg) enhances skeletal muscle function through metabolic reprogramming in normal ICR mice. HISPRO significantly improved muscle performance compared with the control group, including grip strength, rota-rod, and treadmill. Histological and biochemical analyses revealed a shift toward oxidative muscle phenotype compared with the control group, with larger muscle fibers and succinate dehydrogenase-positive fibers. Consistently, HISPRO promoted mitochondrial biogenesis and oxidative metabolism compared with the control group, as evidenced by upregulation of mitochondrial regulatory genes, mitochondrial DNA copy number, citrate synthase activity, and oxidative phosphorylation (OXPHOS) complex levels in skeletal muscles. Mechanistically, HISPRO was associated with activation of the SIRT1-PGC1α-AMPK signaling axis compared with the control group, as evidenced by increased Nampt and Nmnat1 expression, an elevated NAD⁺/NADH ratio, and enhanced AMPK phosphorylation. SIRT1 inhibition markedly attenuated HISPRO-induced increases in mitochondrial biogenesis markers but did not fully suppress OXPHOS protein expression, suggesting the involvement of both SIRT1-dependent and -independent mechanisms. Notably, HISPRO also improved muscle function in dexamethasone-induced muscle atrophy model. It restored mitochondrial biogenesis and function, and suppressed atrophy-related markers compared with the dexamethasone-treated group. HISPRO may contribute to improving muscle quality through coordinated metabolic regulation and could represent a complementary nutritional for supporting muscle metabolic health.

Aims: Our study demonstrated the therapeutic effects of CycloZ on pulmonary inflammation using bleomycin (BLM)-induced pulmonary fibrosis mouse model. Methods: ICR mice were intravenously injected BLM at a 75 mg/kg dose and orally administered either CycloZ (15 mg/kg/day) or pirfenidone (300 mg/kg/day) for 28 days. Lung function and micro-CT imaging analyses were conducted before sacrifice, and lung tissue samples were analyzed for molecular features. Results: The administration of CycloZ resulted in improved lung compliance, total elastance, and tissue elastance, as well as increased aeration area of the lung. Additionally, it led to the recovery of molecular fibrotic features, including excessive inflammatory cytokines, extracellular matrix, and mesenchymal markers. CycloZ also ameliorated immune cell infiltration. RNA-sequencing analysis revealed that CycloZ treatment reversed gene expression patterns associated with inflammation and translation. Conclusions: The results of our study suggest that CycloZ may serve as a novel drug for IPF. It was observed to reverse the expression of multiple genes affected by the fibrotic agent BLM, indicating its potential therapeutic benefits.