Sources, Degradation, Ingestion and Effects of Microplastics on Humans: A Review.

Celluloid, the predecessor to plastic, was synthesized in 1869, and due to technological advancements, plastic products appear to be ubiquitous in daily life. The massive production, rampant usage, and inadequate disposal of plastic products have led to severe environmental pollution. Consequently, reducing the employment of plastic has emerged as a pressing concern for governments globally. This review explores microplastics, including their origins, absorption, and harmful effects on the environment and humans. Several methods exist for breaking down plastics, including thermal, mechanical, light, catalytic, and biological processes. Despite these methods, microplastics (MPs, between 1 and 5 mm in size) continue to be produced during degradation. Acknowledging the significant threat that MPs pose to the environment and human health is imperative. This form of pollution is pervasive in the air and food and infiltrates our bodies through ingestion, inhalation, or skin contact. It is essential to assess the potential hazards that MPs can introduce. There is evidence suggesting that MPs may have negative impacts on different areas of human health. These include the respiratory, gastrointestinal, immune, nervous, and reproductive systems, the liver and organs, the skin, and even the placenta and placental barrier. It is encouraging to see that most of the countries have taken steps to regulate plastic particles. These measures aim to reduce plastic usage, which is essential today. At the same time, this review summarizes the degradation mechanism of plastics, their impact on human health, and plastic reduction policies worldwide. It provides valuable information for future research on MPs and regulatory development.

Delivery of CD151 by Ultrasound Microbubbles in Rabbit Myocardial Infarction.

OBJECTIVES: We aimed to evaluate whether ultrasound (US) and microbubble-mediated delivery of Cluster of Differentiation 151 (CD151) could enhance the therapeutic effects of CD151 on myocardial infarction (MI). METHODS: A rabbit model of MI was established by a modified Fujita method. Then, 50 MI rabbits were randomly divided into 5 groups, including G1 (CD151 plasmid and physiological saline in the presence of US); G2 (CD151 and Sonovue in the presence of US); G3 (CD151 and Sonovue in the absence of US); G4 (Sonovue in the absence of US), and a control group (physiological saline in the absence of US). After 14 days of treatment, the expression of CD151 was detected by Western blot. Besides, vessel density of peri-infarcted myocardium was measured by immunohistochemistry, and cardiac function was analyzed by echocardiography. RESULTS: The rabbit model of MI was established successfully. CD151 injection increased the expression of CD151 and microvessel density in the myocardium of MI rabbits. Heart function was significantly improved by CD151, which exhibited increased left ventricular ejection fraction, left ventricular fractional shortening and a reduced Tei index. Besides, US Sonovue significantly increased the expression efficiency of CD151. CONCLUSION: US microbubble was an effective vector for CD151 delivery. CD151 might be an effective therapeutic target for MI.

Inhibitory effects of subcutaneous tumors in nude mice mediated by low-frequency ultrasound and microbubbles.

The aim of the present study was to investigate the sonication effects of 21-kHz ultrasound (US) with microbubbles (MBs) on the subcutaneous prostate tumors of nude mice. In total, 15 tumor-bearing nude mice were divided into three groups: The control group, the low-frequency US group and the US+MB group. The MBs used were from US contrast agent SonoVue. The parameters of the US were as follows: 21 kHz, 26 mW/cm2 and a 40% duty cycle (2 sec on, 3 sec off) for 3 min, once every other day for 2 weeks. Color Doppler flow imaging, hematoxylin and eosin (HE) staining, immunoblotting and transmission electron microscopy (TEM) were used to evaluate the results. Following 2 weeks of treatment, the blood flow signal disappeared in the US+MB group only, and the tumor size was smaller when compared with the control and US groups. For the immunoblotting, the intensity of cyclooxygenase-2 and vascular endothelial growth factor in the US+MB group was lower compared with the other two groups. Tumor necrosis was present and the nucleus disappeared upon HE staining in the US+MB group. Upon TEM analysis, increased cytoplasmic vacuolation and dilatation of the perinuclear cisternae of the tumor cells were found in the US+MB group. In the control and US groups, the tumors had intact vascular endothelia and vessel lumens. However, lumen occlusion of the vessels was observed in the US+MB group. In conclusion, 21-kHz low-intensity US with MBs may result in vessel occlusion and growth inhibitory effects in the subcutaneous tumors of nude mice.

Effects of low-frequency ultrasound combined with microbubbles on benign prostate hyperplasia.

INTRODUCTION: Our objective is to assess the effects of low-frequency ultrasound combined with microbubbles on benign prostate hyperplasia (BPH). METHODS: Sixteen Beagle dogs with BPH were randomly assigned into 4 groups (n = 4): control group (without treatment), G1 group (injection with 2 mL of microbubble contrast agent); G2 group (21 kHz ultrasound); and G3 group (injection with 2 mL of micro-bubble contrast agent +21 kHz ultrasound). The histopathological damage to prostate cells was assessed via transmission electron microscopy and optical microscopy. The protein expressions of prostate-specific antigen (PSA), inducible nitric oxide synthase (iNOS), superoxide dismutase (SOD) of vessels were detected by enzyme-linked immunosorbent assay (ELISA). RESULTS: Histopathologically, the prostate cells exhibited nuclear chromatin contraction, mitochondrial swelling, degranulation of rough endoplasmic reticulum, basement membrane rupture and cell apoptosis in the G2 and G3 groups; it was especially obvious in the G3 group, while no changes were observed in the control and G1 groups. Although prostate volume using imaging was not significantly changed in all groups after treatment, PSA was significantly reduced in the G2 and G3 groups, and especially obvious in the G3 group (p < 0.05). The iNOS and SOD, which are important oxidative stress factors, significantly increased after treatment in the G2 and G3 groups, but not in the control and G1 groups (p < 0.05). CONCLUSIONS: Low-frequency ultrasound is effective in treating BPH; low-frequency ultrasound combined with microbubbles improves the treatment efficacy.

Effects of low-frequency ultrasound and microbubbles on angiogenesis-associated proteins in subcutaneous tumors of nude mice.

It has been shown that 1 and 3 MHz low-intensity ultrasound was able to affect the fragile and leaky angiogenic blood vessels in a tumor. However, the biological effects of 21 kHz low-intensity ultrasound on tumors remain unclear. The aim of the present study was to explore the effects of 21 kHz ultrasound with microbubbles on the regulation of vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2) and apoptosis in subcutaneous prostate tumors in nude mice. The study included three parts, each with 20 tumor-bearing nude mice. Twenty nude mice were divided into four groups: control (sham treatment), microbubble ultrasound contrast agent (UCA), low-frequency ultrasound (US) and US+UCA groups. The UCA used was a microbubble contrast agent (SonoVue). The parameter of ultrasound: 21 kHz, an intensity of 26 mW/cm2, 40% duty cycle (on 2 sec, off 3 sec), 3 min, once every other day for 2 weeks. In the first study, all subcutaneous tumors were examined by contrast-enhanced ultrasonography (CEUS) at the initiation and completion of the experiments. Peak intensity (PI), time to peak intensity (TTP) and area under the curve (AUC) on the time intensity curve (TIC) were analyzed. In the second study, the intensity of VEGF and COX-2 protein expression in the vascular endothelium and cytoplasm was evaluated using immunohistochemistry and laser confocal microscopy. In the third study, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay was used for the evaluation of cell apoptosis in tumor tissues. The tumor cells and vasculature were examined by transmission electron microscopy (TEM). Only in the US+UCA group, PI and AUC decreased. The intensity of COX-2 and VEGF in the US+UCA group in immunohistochemical staining and laser confocal microscopy was lower compared to that of the other three groups. More cell apoptosis was found in the US+UCA group compared to the other 3 groups. In the control, UCA and US groups, the tumors had intact vascular endothelium and vessel lumens in TEM. However, lumen occlusion of vessels was observed in the US+UCA group. Twenty-one kHz low-intensity ultrasound with microbubbles may have anti-angiogenic effects on subcutaneous tumors in nude mice.