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BackgroundSilicosis is a diffuse fibrosis of the lungs caused by long-term inhalation of free silicon dioxide (SiO2). It has a complex pathogenesis and lacks effective treatment. Brusatol (Bru) has a variety of biological activities, and its role in silicosis fibrosis is unclear yet. ObjectiveTo investigate the effects of different concentrations of Bru on SiO2-induced silicosis fibrosis in mice. MethodsThirty male C57BL/6J mice were randomly divided into five groups: a control group, a silica group, and three Bru intervention groups with low, medium, and high doses (1, 2, and 4 mg·kg−1), with 6 mice in each group. Except the control group, the remaining groups were established as SiO2-induced silicosis mouse models by using a single tracheal infusion of 50 μL 60 mg·mL−1 SiO2 suspension. The control group was dosed with equal amount of saline. The Bru intervention groups were injected intraperitoneally with Bru for 5 consecutive days and then injected every other day. After 28 d of exposure, the mice were executed and lung tissues were collected. The lung coefficient of the mice was measured, and the pathological changes of the lung tissues were observed after hematoxylin-eosin (HE) and Masson staining. The levels of apoptotic protein Cleaved-caspase 3, fibrosis-related protein α-smooth muscle actin (α-SMA), type I collagen (Col-I), autophagy-associated protein Beclin1, microtubule-associated protein 1 light chain 3 (LC3), Sequestosome 1 (p62/SQSTM1), Kelch like ECH-associated protein-1 (Keap1), and nuclear factor erythroid 2 related factor 2 (Nrf2) were detected by Western blot. The mRNA levels of Caspase 3, α-SMA, and Col-I were measured by realtime fluorescence-based quantitative PCR. ResultsCompared with the control group, the lung coefficient of mice in the silica group was significantly increased (P < 0.01); the lung tissues of the silicosis mice showed damaged alveolar walls, along with infiltration of inflammatory cells, fibrous nodules, and collagen deposition; furthermore, the protein and mRNA levels of Cleaved-caspase 3, α-SMA, and Col-I were significantly increased (P < 0.01); the expression levels of Beclin1, LC3-II/I, p62, and Nrf2 were increased, while that of Keap1 was decreased (P < 0.05). The interventions with low and medium doses of Bru reduced lung coefficient (P < 0.05) and protected against pathological damage and collagen deposition in the lung tissues of the silicosis mice; the protein and mRNA expression levels of Cleaved-caspase 3, α-SMA, and Col-I were significantly decreased in the low and medium dose groups (P < 0.05, P < 0.01), the expression levels of Beclin1, LC3-II/I, p62, and Nrf2 were also decreased (P < 0.05, P < 0.01), and the expression level of Keap1 was increased in the medium dose group (P < 0.05). However, compared with the silica group, the differences in lung coefficient, pathological damage, and protein and mRNA expression levels of Cleaved-caspase 3, α-SMA, and Col-I in the Bru high dose group were not statistically significant (P > 0.05). In addition, the high dose of Bru decreased Beclin1, LC3-II/I, and Nrf2 expression levels (P < 0.01), did not change p62 protein expression level (P > 0.05), while increased Keap1 protein level (P < 0.01). ConclusionLow and medium doses of Bru might regulate autophagy through the Keap1-Nrf2 pathway, ameliorate autophagic degradation impairment, reduce pulmonary coefficient, attenuate apoptosis, and delay the progression of fibrosis in SiO2-induced silicosis mice.

Alternatives to fish meal (FM) in fish feed are urgently required in aquaculture. We therefore examined the effect of replacing FM with a complex protein source (CPS) comprising soybean meal, peanut meal, corn protein meal, feather meal, and yeast protein, on carp (Cyprinus carpio) growth, body composition, lipidomics, and flesh quality. Lipidomics analysis was conducted to reveal the impact of dietary changes on fish lipid composition and metabolism, which is closely related to flesh quality and nutritional value. Over an eight-week growth trial, fish meal was replaced with CPS at 0 % (FM only), 20 %, 40 %, 60 %, 80 %, or 100 %. Weight gain and other growth parameters did not differ significantly among the treatments. Lipid deposition (LD) was positively correlated, and protein deposition negatively correlated, with CPS levels. LD and fillet ether extract were significantly elevated at 100 % CPS, whereas superoxidase dismutase expression, claudin-1 expression, and lipase activity were significantly reduced. The n-3 PUFA level and n-3/n-6 PUFA ratio were significantly lower following CPS feeding, reducing flesh quality. These findings indicate that CPS successfully replaced 60–80 % of dietary FM in carp diets, while the 100 % replacement group provided insights into the comprehensive effects of total substitution. Future studies will further optimize formulations based on these results to resemble practical production more closely. CPS with nutrient supplementation may therefore present a viable and safe partial replacement for dietary FM.