With the rapid advancement of modern science and technology, human exposure to radioactive factors has continuously increased, and radiation induced functional damage to various systems and organs in the human body has grown accordingly [1,2]. Therefore, exploring safe, non toxic and effective radioprotective agents has long been a hot topic in radioprotection research worldwide.
In recent years, research on radioprotective agents has gradually expanded from conventional chemical drugs to natural anti radiation medicines and functional foods [3]. Pollen, the reproductive material of seed plants, is rich in nutrients and various bioactive substances, hence hailed as a “complete nutritional food” [4]. It exerts multiple biological effects including immune regulation, anti fatigue, anti tumor, free radical scavenging, inhibition of benign prostatic hyperplasia, liver protection, improvement of nervous system function, and anti radiation activity [5,6]. Rape bee pollen contains 18 amino acids (including 8 essential amino acids for humans), 11 vitamins, 25 mineral elements, as well as carbohydrates, lipids, enzymes and hormones. It possesses free radical scavenging, antioxidant and anti proliferative effects on the prostate [7].
Over the past two decades, scholars and medical researchers globally have extensively investigated the pharmacological effects and therapeutic efficacy of bioactive components such as polysaccharides, vitamins and trace elements in pollen on human health. However, few studies have focused on the biological functions of rape bee pollen, and there have been no reports regarding the radioprotective effects of enzymatic hydrolyzed peptides from rape pollen (PRPG) against high dose irradiation. This paper systematically investigates the impacts of PRPG on hematopoietic function in mice with high dose radiation injury, aiming to provide evidence for developing safe, non toxic and effective anti radiation drugs and open a new avenue for the utilization of rape bee pollen.
01 Objectives and Methods
This study aimed to investigate the effects of PRPG on hematopoietic function in mice injured by 8 Gy ⁶⁰Co-γ-ray irradiation, so as to provide a basis for developing safe, non-toxic and effective anti-radiation agents and improving the added value of pollen.
Mice were randomly divided into the blank control group, irradiation control group, and low, medium and high dose PRPG groups. Samples were intragastrically administered to mice for 30 consecutive days, followed by single dose whole body irradiation with 8 Gy ⁶⁰Co-γ-rays. Peripheral blood was collected from the tail vein at regular intervals post-irradiation for hematological analysis. At day 20 after irradiation, the micronucleus rate and DNA content of bone marrow cells, hepatic superoxide dismutase (SOD) activity, and serum malondialdehyde (MDA) level were determined.
02 Results and Analysis
Effects of PRPG on Peripheral Blood Routine in Irradiated Mice
The bone marrow hematopoietic system is highly radiosensitive. Ionizing radiation mainly damages hematopoietic stem cells, leading to hypo-function or failure of hematopoiesis. After exposure to a certain dose of radiation, bone marrow hematopoietic function is altered, manifested as a sharp decline in various peripheral blood cells, among which white blood cell (WBC) count reflects the degree of blood system injury. In this experiment, the levels of WBC, red blood cell (RBC), platelet (PLT) and hemoglobin (HGB) in mouse peripheral blood were detected.
Figure 1 showed that the WBC count in mice decreased significantly after irradiation, reaching the minimum at day 3, then slowly rebounded with fluctuations starting from day 5. The medium-dose PRPG group showed a significant difference compared with the irradiation control group (p<0.05). At day 20 post-irradiation, the medium- and high-dose PRPG groups exhibited significant differences relative to the irradiation control group (p<0.05). WBC counts in all PRPG-treated groups increased markedly, with the medium-dose group showing the greatest recovery, though none returned to normal levels. These results indicated that PRPG could significantly elevate WBC counts in irradiated mice.
Effects of PRPG on Red Blood Cells (RBC) in Irradiated Mice
As shown in Figure 2, RBC counts in all groups continuously declined after irradiation at different rates, with the irradiation control group decreasing the fastest. RBC counts reached the minimum at day 7 post-irradiation and then began to rise. At day 9, the medium- and high-dose PRPG groups had significantly higher RBC counts than the irradiation control group (p<0.05). At day 20, RBC counts in all PRPG groups increased obviously and were significantly different from the irradiation control group (p<0.05), with the medium-dose group showing the highest RBC level, which was also significantly higher than other PRPG dose groups (p<0.05). It suggested that PRPG could increase RBC counts in irradiated mice to a certain extent.
Figure 3 demonstrated that PLT counts in all groups continuously declined after irradiation, with the irradiation control group decreasing most rapidly. At day 9, all PRPG groups showed significant differences from the irradiation control group (p<0.05), with PLT counts dropping to the lowest point (the irradiation control group had the minimum value), followed by a slow recovery. At day 20, PLT counts in all groups recovered to a certain level but not to normal values; the medium-dose PRPG group was significantly different from the irradiation control group (p<0.05). This indicated that PRPG could raise PLT counts in irradiated mice moderately.
Effects of PRPG on Hemoglobin (HGB) in Irradiated Mice
Figure 4 showed that HGB levels in all groups continuously decreased after irradiation, with the irradiation control group declining the fastest and reaching the minimum at day 9, followed by slow recovery. The medium-dose group had the fastest rebound. At day 20, the medium- and high-dose PRPG groups were significantly different from the irradiation control group (p<0.05). HGB levels in mice increased moderately but did not return to normal, implying that PRPG could elevate HGB levels in irradiated mice to a certain degree.
In summary, WBC counts in all irradiated groups reached the minimum at day 3 post-irradiation, while RBC, HGB and PLT levels declined later than WBC, indicating that WBCs were the most radiosensitive blood cells. At day 20, although WBC, RBC, PLT and HGB levels in all PRPG-treated irradiated mice failed to return to normal, they were significantly higher than those in the irradiation control group.
Effects of PRPG on Micronucleus Rate of Bone Marrow Cells in Irradiated Mice
As shown in Table 1, irradiation induced chromosomal damage to mouse genetic material, resulting in generally increased micronucleus rates in all irradiated groups, which were higher than that in the blank control group. Among PRPG-treated groups, the medium-dose group had the lowest micronucleus rate. All PRPG groups showed significant differences from both the irradiation control group and the blank control group (p<0.05). PRPG reduced the micronucleus rate in irradiated mice, which still remained above the normal level. These findings suggested that PRPG could moderately decrease the micronucleus rate and alleviate radiation-induced chromosomal damage in mice.
Effects of PRPG on Bone Marrow DNA Content in Irradiated Mice
DNA bears vital physiological functions including inheritance, initiation of cell division and regulation of protein biosynthesis; thus, radiation-induced DNA damage is regarded as the primary injury of biological macromolecules. As presented in Table 1, bone marrow DNA contents in mice orally administered with PRPG were higher than those in the irradiation control group, yet without significant differences (p>0.05). It indicated that PRPG exerted a protective effect against radiation-induced reduction of bone marrow DNA content in mice.
Effects of PRPG on Superoxide Dismutase (SOD) Activity in Irradiated Mice
SOD is a natural free radical scavenger, whose activity reflects the body’s capacity to eliminate free radicals. Table 2 showed that hepatic SOD activity in mice intragastrically treated with PRPG was higher than that in the irradiation control group after irradiation, with significant differences observed in all PRPG-treated groups (p<0.05). It demonstrated that PRPG could effectively enhance tissue SOD activity and possess potent antioxidant capacity.
Effects of PRPG on MDA Content in Irradiated Mice
MDA is a terminal product of lipid peroxidation triggered by free radical attack on biological membranes. Its level reflects the extent of lipid peroxidation and free radical-mediated damage to the organism. As shown in Table 2, oral administration of PRPG significantly decreased serum MDA levels in irradiated mice, with the medium-dose group reaching 57.21% of the irradiation control group. All PRPG-treated groups were significantly different from the irradiation control group (p<0.05). These results indicated that PRPG could markedly mitigate lipid peroxidation and free radical-induced damage in irradiated mice, exhibiting strong antioxidant activity.
03 Discussion
Hematopoietic tissue is highly radiosensitive, with hematopoietic stem cells of various lineages as the main target organs of radiation injury. Irradiation commonly causes adverse outcomes such as leukopenia, myelosuppression, destruction of hematopoietic microenvironment, DNA damage, decreased SOD activity and elevated MDA levels [14]. Bioactive substances including active peptides, oligosaccharides and trace elements may restore the hematopoietic system by regulating the secretion of hematopoietic-related cytokines, meanwhile enhancing the body’s free radical-scavenging capacity and alleviating hematopoietic tissue damage, thereby exerting anti-radiation effects [3].
Radiation-induced damage to the hematopoietic system leads to hypo-function or failure of hematopoiesis, accompanied by marked reductions in peripheral WBC, RBC and PLT counts, which further induce complications such as infection, anemia and hemorrhage [15]. Our results revealed that peripheral WBC, RBC and PLT counts in PRPG-treated irradiated mice were significantly higher than those in the irradiation control group, consistent with a previous report that alcohol-soluble functional corn peptides markedly increased WBC and PLT counts in irradiated mice. This indicated that PRPG could mitigate radiation-induced peripheral blood routine damage in mice to a certain extent.
Our experimental results showed that PRPG reduced the micronucleus rate and elevated DNA content of bone marrow cells in irradiated mice. Micronuclei are small secondary nuclei formed when chromosomes regularly segregate into daughter cells during late mitosis, named for their much smaller size than cell nuclei. Increased micronucleus rate of bone marrow cells is one of the major cytogenetic indicators of radiation injury in mice. Within a certain range, irradiation dose is positively correlated with the micronucleus rate of bone marrow cells, while recovery time is negatively correlated with it; the number of micronuclei in bone marrow cells reflects chromosomal damage [12]. The lower micronucleus rate in PRPG-treated mice compared with the irradiation control group suggested that PRPG could repair radiation-damaged chromosomes to some extent.
SOD is a natural free radical scavenger with higher activity corresponding to stronger free radical-scavenging capacity; MDA is a key intermediate product of radiation-induced oxidation, whose lower level indicates slighter radiation injury. PRPG increased hepatic SOD activity and significantly decreased serum MDA levels in irradiated mice, which demonstrated its ability to effectively inhibit radiation-induced oxidative damage and reduce the harm of irradiation to the hematopoietic system in mice.
04 Conclusion
PRPG can improve peripheral blood routine indices (WBC, RBC, PLT and HGB counts) in mice exposed to single-dose 8 Gy acute irradiation, reduce the micronucleus rate and increase DNA content of bone marrow cells to protect the bone marrow hematopoietic system. It also elevates hepatic SOD activity and decreases serum MDA levels in irradiated mice, enhancing their antioxidant capacity and mitigating radiation-induced damage to the hematopoietic system. In summary, PRPG exerts protective effects on hematopoietic function in mice with acute radiation injury induced by 8 Gy irradiation. However, its specific mechanism remains unclear and requires further in-depth research.
References
[1] Zhang X G, Qiang Y Z. Thoughts on radiation immunology[J]. Chinese Journal of Radiological Medicine and Protection, 2004, 24(2):180-183.
[2] Ishikawa F, Nakano H, Seo A, et al. Irradiation up-regulates CD80 expression through induction of tumor necrosis factor alpha and CD40 ligand expression on B lymphoma cells [J]. Immunology, 2002, 106: 354-362.
[3] Huang D J, Huang D C, Liao X F, et al. Research progress on anti-damage effects of natural radioprotective substances[J]. Chinese Journal of Radiological Health, 2008, 12(4):511-512.
[4] Zhou X L. Pharmacological effects and application research of pollen[J]. Heilongjiang Medicine Journal, 2009, 22(2):152-155.
[5] Chen S H. Various health-care functions of pollen[J]. China Health Food, 2002,15(6): 33-34.
[6] Campos M G, Webby R F, Markham K R. Age-induced diminution of free radical scavenging capacity in bee pollens and the contribution of constituent flavonoids [J]. Journal of Agricultural and Food Chemistry, 2003, 51: 742-745.
[7] Sun L P, Zhu X L, Zhang Z W, et al. Study on scavenging superoxide anion free radicals by enzymatic hydrolyzed rape bee pollen[J]. Chinese Agricultural Science Bulletin, 2007,23(9):144-148.
[8] Hu X B, Luo Z Y, Wu M C. Study on optimal extraction technology of glutelin from rape pollen[J]. Food Science, 2006,27(10):354-359.
[9] Miao Q L, Zhu L, Chen X H, et al. Protective effects of scallop polypeptides on ⁶⁰Co-γ-ray-irradiated mice[J]. Chinese Journal of Marine Drugs, 2005,24(1):28-32.
[10] Li D Y, Zhou Y Z, Yu Y L, et al. Anti-radiation effects of ginkgo leaf flavonoids[J]. Acta Nutrimenta Sinica, 2004,26(3):120-122.
[11] Yan Y, Xu J H, Yang F. Radioprotective function of soybean peptides[J]. Chinese Journal of Public Health, 2004,20(5):564-565.
[12] Ministry of Health of the People’s Republic of China. Technical Standards for Testing and Evaluation of Health Foods[S]. 2003:02-14.
[13] Liu B. Study on anti-radiation function of housefly larva extracts[D]. Master’s Thesis, Huazhong Agricultural University, 2006.
[14] Hosseininehr S J. Foundation review: Trends in the development of radioprotective agents [J]. Drug Discovery Today, 2007, 12 (19/20): 794-805.
[15] Chen H M, Jiang D W, Kan G S. Radioprotective effects of alcohol-soluble functional corn peptides in mice[J]. Food Research and Development, 2008,29(6):8-10.
Post time: May-18-2026
