Injury in Minipig Parotid Glands following Fractionated Exposure to 30 Gy of Ionizing Radiation

Rapamycin alleviates irradiation-induced parotid injury by enhancing the whole gland homeostasis

OBJECTIVES

Salivary gland injury is one of the most common complications of radiotherapy in head-and-neck cancers. This study investigated the mechanism by which rapamycin prevents irradiation (IR)-induced injury in the parotid glands.

MATERIALS AND METHODS

Miniature pigs either received (a) no treatment (NT), (b) IR in the right parotid gland for 5 consecutive days (IR), or intraperitoneal administration of rapamycin (Rap) 1 h prior to IR (IR + Rap). Tissues were collected at three distinct time points (24 h, 4 weeks, and 16 weeks) after IR. Histological analyses, western blot, and real-time reverse transcriptase-polymerase chain reaction were performed to explore the mechanisms of IR-induced injury in the parotid gland.

RESULTS

Rapamycin treatment maintained parotid salivary flow 16 weeks post-IR, preserved the number of acinar cells, and reduced parotid tissue fibrosis, as well as reduced apoptosis levels, decreased cleaved caspase-3 expression, and increased the Bcl-2/Bax ratio in the parotid glands. Autophagy marker LC3B was upregulated by rapamycin after IR, while P62 expression was downregulated. Rapamycin reduced the expression of pro-inflammatory factors and the mesenchymal tissue fibrosis following IR.

CONCLUSIONS

Rapamycin maintains gland homeostasis after IR by decreasing apoptosis, reducing the expression of pro-inflammatory factors, and enhancing autophagy.

Histological and biochemical evaluation of the effects of silver nanoparticles (AgNps) versus titanium dioxide nanoparticles (TiO2NPs) on rat parotid gland

The unlimited use of nanoparticles (NPs) results in toxic impacts on different tissues. The current study aimed to compare the adverse effects of AgNPs and TiO2NPs on the parotid gland of adult male albino rats as regards the histopathological, immunohistochemical, and biochemical changes, exploring the possible underlying mechanisms and the degree of improvement after cessation of administration. Fifty-four adult male albino rats were divided into control group (I), AgNPs-injected group (II), and TiO2NPs-injected group (III). We measured the levels of tumor necrosis factor-alpha (TNF-α) and interleukin (IL-6) in the serum, and levels of MDA and GSH in parotid tissue homogenate. Quantitative real-time polymerase-chain reaction (qRT-PCR) was used to measure the expression levels of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC1-α), nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4), mouse double minute 2 (MDM2), Caspase-3 Col1a1, and Occludin. Parotid tissue sections were examined by light microscope (Hematoxylin & Eosin and Mallory trichrome stains), electron microscope, and immunohistochemical examination of CD68 and anti-caspase-3 antibodies. Both NPs severely affected the acinar cells and damaged the tight junction between them by enhancing expression of the inflammatory cytokines, inducing oxidative stress, and disturbing the expression levels of the studied genes. They also stimulated fibrosis, acinar cell apoptosis, and inflammatory cells infiltration in parotid tissue. TiO2NPs effects were less severe than AgNPs. Cessation of exposure to both NPs, ameliorated the biochemical and structural findings with more improvement in TiO2NPs withdrawal. In conclusion: AgNPs and TiO2NPs adversely affected the parotid gland, but TiO2NPs were less toxic than AgNPs.

Long non-coding RNA and mRNA profile analysis in the parotid gland of mouse with type 2 diabetes

AIMS

Salivary gland dysfunction is a common complication of diabetes mellitus (DM). Long non-coding RNA (lncRNA) is evidenced to involve in the functional regulation of salivary gland, however, its role in DM-impaired gland is unknown. Therefore, this study aimed to investigate the expression profiles and functional networks of lncRNA in the parotid glands (PGs) of DM mice.

MAIN METHODS

Microarray was used to detect lncRNA and messenger RNA (mRNA) expression profiles in the PGs from db/db and db/m mice. Eleven differently expressed (DE) lncRNAs validated by qRT-PCR were selected for coding-non-coding gene co-expression (CNC) and competing endogenous RNA (ceRNA) network analysis, as well as the following Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Pearson's coefficient correlation analysis was used to analyze the correlations between DE lncRNAs expression and DM pathology.

KEY FINDINGS

By using a 2-fold change and P < 0.05 as the cutoff criteria, 1650 DE lncRNAs (758 upregulated and 892 downregulated) and 1073 mRNAs (563 upregulated and 510 downregulated) were identified in the PGs of db/db mice compared to db/m mice. GO and KEGG analysis of DE mRNA suggested that activated inflammation response and downregulated ion transport might count for the dysfunction of diabetic PG. CNC and ceRNA networks analysis of 11 DE lncRNAs showed that the inflammation process and its related signaling pathways including advanced glycation end product (AGE)-receptor for AGE (RAGE) signaling pathway in diabetic complications, cytokine-cytokine receptor interaction, chemokine signaling pathway, apoptosis, and cell adhesion molecules were significantly enriched. The alterations of lncRNAs were closely correlated with higher blood glucose and serum insulin levels in mice.

SIGNIFICANCE

We identified multiple lncRNAs/mRNAs and several signaling pathways that may involve in the pathogenesis of diabetic salivary injury, providing new insight into potential target of diabetic hyposalivation.

Protective Effect and Mechanism of Action of Rosmarinic Acid on Radiation-Induced Parotid Gland Injury in Rats

The parotid glands are damaged by oxidative stress and a series of pathophysiological changes after irradiation. Rosmarinic acid (RA) is a natural antioxidant that provides a radioprotective effect against harmful damage from ionizing radiation. The present study aims to explore the protective effects of RA on radiation-induced parotid gland injury and its underlying mechanism. Sprague-Dawley rats were irradiated with 15 Gy X-ray and treated with different concentrations of RA (30, 60, and 120 mg/kg) or amifostine (AMI, 250 mg/kg). Saliva secretion function, oxidative stress, apoptosis, the inflammatory response, and fibrosis were determined by the measurement of the salivary flow rate, enzyme-linked immunosorbent assay, transferase-mediated DUTP Nick end labeling, Western blot, quantitative real time polymerase chain reaction, and hematoxylin and eosin staining. Here, we show that RA treatment significantly attenuated reactive oxygen species by a direct hindrance effect and the indirect activation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha/nicotinamide adenine dinucleotide phosphate oxidase 4 signaling. Rosmarinic acid not only reduced apoptosis by inhibiting p53/jun N-terminal kinase activation but also reduced parotid gland tissue fibrosis by downregulating inflammatory factor levels. Compared to AMI, RA has the obvious advantages of late efficacy and convenient usage. Moreover, 60 mg/kg is the minimum effective dose of RA. Therefore, RA can potentially be applied as a therapeutic radioprotective agent to treat radiation-induced parotid gland injury in the future.

Mechanisms of Antiulcer Effect of an Active Ingredient Group of Modified Xiao Chaihu Decoction

The present study aimed to investigate the antiulcer activities and mechanisms of action of an active ingredient group (AIG) of Modified Xiao Chaihu Decoction (MXCD). The gastroprotective action of the AIG was studied in ethanol-induced, pylorus ligature-induced, and acetic acid-induced in vivo gastric ulcer models. The enzyme-linked immunoadsorbent assay (tumor necrosis factor-α (TNF-α), prostaglandin E₂ (PGE₂), and epidermal growth factor (EGF)), nitrate reductase assay (nitric oxide (NO)), western blot analysis (Bax, Bcl-2, cleaved-caspase-3, and cleaved-PARP (poly (ADP-Ribose) polymerase)), histological analysis (HE), and immunohistochemical analysis (HSP-70, p-AKT, and PCNA) were used to evaluate the anti-inflammatory, antiapoptotic, and healing properties of AIG. Numerous mechanisms are involved in the antiulcer activity of AIG, including the increase of PGE₂, NO, and EGF content and a reduction in TNF-α levels. The upregulation of HSP-70, p-AKT, and PCNA seems to be directly linked to the healing effect of AIG. Bax, Bcl-2, cleaved-caspase-3, and cleaved-PARP also play a key role in this process. The AIG exerted gastroprotective effects by reducing antisecretory, anti-inflammatory, and antiapoptotic mechanisms. In addition, it promotes cell proliferation. Therefore, activation of the PI3K/AKT signaling pathway may play an important role in cell proliferation.

Development of a minipig model for lung injury induced by a single high-dose radiation exposure and evaluation with thoracic computed tomography

Radiation-induced lung injury (RILI) due to nuclear or radiological exposure remains difficult to treat because of insufficient clinical data. The goal of this study was to establish an appropriate and efficient minipig model and introduce a thoracic computed tomography (CT)-based method to measure the progression of RILI. Göttingen minipigs were allocated to control and irradiation groups. The most obvious changes in the CT images after irradiation were peribronchial opacification, interlobular septal thickening, and lung volume loss. Hounsfield units (HU) in the irradiation group reached a maximum level at 6 weeks and decreased thereafter, but remained higher than those of the control group. Both lung area and cardiac right lateral shift showed significant changes at 22 weeks post irradiation. The white blood cell (WBC) count, a marker of pneumonitis, increased and reached a maximum at 6 weeks in both peripheral blood and bronchial alveolar lavage fluid. Microscopic findings at 22 weeks post irradiation were characterized by widening of the interlobular septum, with dense fibrosis and an increase in the radiation dose-dependent fibrotic score. Our results also showed that WBC counts and microscopic findings were positively correlated with the three CT parameters. In conclusion, the minipig model can provide useful clinical data regarding RILI caused by the adverse effects of high-dose radiotherapy. Peribronchial opacification, interlobular septal thickening, and lung volume loss are three quantifiable CT parameters that can be used as a simple method for monitoring the progression of RILI.