Effects of low dose radiation on immune cells subsets and cytokines in mice

Cytokine storm modulation using cholecalciferol and low dose gamma radiation in Escherichia coli infected mice

This work investigates the efficiency of cholecalciferol and low dose gamma radiation in modulating cytokine storm through their impact on inflammatory and anti-inflammatory cytokine and protecting against lung and liver injuries. Male Swiss albino mice were exposed to 0.2 Gy gamma radiation/week for four consecutive weeks then injected intraperitoneally (i.p) with a single dose of 8.3 × 106 CFU Escherichia coli/g b.w. then injected i.p. with 1.0 mg/kg cholecalciferol (Vit D3) for 7 days starting 4 h after E. coli injection. The results revealed that Cholecalciferol and low dose gamma radiation caused significant depletion in the severity of E. coli infection (colony forming unit per milliliter), log10 of E. coli, Tumor necrosis factor alpha, Interleukin 6, VEGF, alanine aminotransferase, and aspartate aminotransferase levels and significant elevation in IL-10, IL-4, and HO-1. Immunohistochemical analysis of caspase-3 expression in lung tissue section showed low caspase-3 expression in cholecalciferol and low dose gamma radiation treated group. Histopathological examinations were performed in both lung and liver tissues which also emphasis the biochemical findings. Our results exhibit the importance of cholecalciferol and low dose gamma radiation in improving liver function and providing anti-inflammatory response in diseases causing cytokine storm.

Sequential radiation exposure: uncovering the potential of low dose ionizing radiation in mitigating high dose effects on immune cells

PURPOSE

The radioadaptive response refers to a phenomenon wherein exposure to a low dose of ionizing radiation (LDIR) can induce a protective response in cells or organisms, reducing the adverse effects of a subsequent higher dose of ionizing radiation (HDIR). However, it is possible to administer the low dose after the challenge dose. This study was conducted to determine the potential mitigating effect of LDIR administered after HDIR on mice immune cells.

MATERIALS AND METHODS

Alongside the conventional adaptive response setting, one group of mice was initially exposed to HDIR and subsequently treated with LDIR. Neutrophil activation was done using DHR-reducing assay and cell proliferation was evaluated through CFSE-dilution assay in helper (CD4+) and cytotoxic (CD8+) T cells. Cytokine production by these T cell subsets was also assessed by intracellular staining using flow cytometry.

RESULTS

The results of this study revealed no change in neutrophil function between any of the mice groups compared to the untreated control group. Although significant changes were not detected in the proliferation of CD4+ T cells, decreased proliferation was observed in stimulated CD8+ T cells in the HDIR group. In contrast to IFN-ɣ, which showed no evident change in either of the T cell subsets after stimulation, IL-4 was rigorously dropped in stimulated CD4+ T cells in the HDIR group.

CONCLUSIONS

In summary, the results of this study indicated that the administration of LDIR to mice before HDIR was not able to reduce the detrimental effects of HDIR in our experimental setting. Instead, we observed a mitigating effect of LDIR when administered after the challenge dose. This suggests that not only the dose and duration but also the order of LDIR relative to HDIR affects its efficacy.

Interplay of immune modulation, adaptive response and hormesis: Suggestive of threshold for clinical manifestation of effects of ionizing radiation at low doses?

The health impacts of low-dose ionizing radiation exposures have been a subject of debate over the last three to four decades. While there has been enough evidence of "no adverse observable" health effects at low doses and low dose rates, the hypothesis of "Linear No Threshold" continues to rule and govern the principles of radiation protection and the formulation of regulations and public policies. In adopting this conservative approach, the role of the biological processes underway in the human body is kept at abeyance. This review consolidates the available studies that discuss all related biological pathways and repair mechanisms that inhibit the progression of deleterious effects at low doses and low dose rates of ionizing radiation. It is pertinent that, taking cognizance of these processes, there is a need to have a relook at policies of radiation protection, which as of now are too stringent, leading to undue economic losses and negative public perception about radiation.

Why Low-level Radiation Exposure Should Not Be Feared

ABSTRACT

The purpose of this paper is to address the public fear that is usually associated with low-level radiation exposure situations. Its ultimate objective is to provide persuasive assurances to informed but skeptical members of the public that exposure situations involving low-level radiation are not to be feared. Unfortunately, just acquiescing to an unsupportive public fear of low-level radiation is not without consequences. It is causing severe disruptions to the benefits that harnessed radiation can produce for the well-being of all humanity. In this pursuit, the paper provides the scientific and epistemological basis needed for regulatory reform by reviewing the history in quantifying, understanding, modeling, and controlling radiation exposure, including some of the evolving contributions of the United Nations Scientific Committee on the Effects of Atomic Radiation, the International Commission on Radiological Protection, and the myriad of international and intergovernmental organizations establishing radiation safety standards. It also explores the various interpretations of the linear no-threshold model and the insights gained from radiation pathologists, radiation epidemiologists, radiation biologists, and radiation protectionists. Given that the linear no-threshold model is so deeply imbedded in current radiation exposure guidance, despite the lack of a solid scientific base on the actually proven radiation effects at low-doses, the paper suggests near-term ways to improve regulatory implementation and better serve the public by excluding and/or exempting trivial low-dose situations from the regulatory scope. Several examples are given where the unsubstantiated public fear of low-level radiation has resulted in crippling the beneficial effects that controlled radiation offers to a modern society.

Low dose radiation therapy attenuates ACE2 depression and inflammatory cytokines induction by COVID-19 viral spike protein in human bronchial epithelial cells

Purpose: Low-dose radiation therapy (LDRT) is an evidence-based anti-inflammatory treatment. In anti-COVID-19, our study suggests that low to moderate dose radiation of < 1.5 Gy can inhibit the induction of inflammatory cytokine and attenuate the ACE2 depression induced by spike protein in human bronchial epithelial cells in COVID-19 infection. Our study provided further mechanistic evidence to support LDRT as a cost-effective treatment for COVID-19 to relieve the severe inflammatory reaction and lung injury. Methods and materials: A cellular model was created by treating human bronchial epithelial cells (BEP2D) with SARS-CoV-2 spike protein. We used the qRT-PCR and ELISA analysis to identify the production of inflammatory cytokines. The BEP2D control cells and the spike-treated cells were irradiated using a single low to moderate dose radiation of 0.5 Gy, 1 Gy, and 1.5 Gy. The inflammatory cytokines and ACE2 expression were detected at different time points. Results: The soluble SARS-CoV-2 spike protein stimulated the formation of inflammatory cytokines IL-6 and TNF-α while reducing the ACE2 protein expression in human bronchial epithelial cells. A single low to moderate dose exposure of 0.5 Gy, 1 Gy, and 1.5 Gy could attenuate the IL-6 and TNF-α induction and rescue the depression of ACE2 by spike protein. Moreover, the spike protein increased the proteolytic degradation of ACE2 protein by promoting NEDD4-mediated ubiquitination of ACE2. Conclusions: The low-dose radiation can attenuate ACE2 depression and inflammatory response produced in the targeted human bronchial epithelial cells by spike protein. This coordinating effect of LDRT may relieve the severe inflammatory reaction and lung injury in COVID-19 patients.

Yiqi Jiedu herbal decoction attenuates the 2 Gy 60Co γ ray induced spleen injury by inhibiting apoptosis and modulating the immune balance

ETHNOPHARMACOLOGICAL RELEVANCE

Irradiation-induced immunosuppression often occurs during radiotherapy in patients, which would increase the risk of opportunistic infections. Many Chinese herbal prescriptions or natural extracts have recently attracted increased radiation protection and therapy attention due to their low toxicity.

AIM OF THE STUDY

The present study aimed to investigate the protective effects of Yiqi Jiedu (YQJD) decoction on spleen injury induced by 2 Gy ⁶⁰Co γ ray in mice.

MATERIALS AND METHODS

A total of 180 Balb/c mice were randomly divided into five groups: blank control (Ctrl), model (IR), positive drug (IRA), low-dose YQJD decoction (IRL), and high-dose YQJD decoction (IRH). After a ten-day intervention, mice were exposed to a single dose of total body irradiation (2 Gy) and sacrificed on the 1^st, 3^rd, and 7^th day after irradiation. The indicators include general observations and body weight, changes in peripheral hemogram, index and histopathology examination of the spleen, distribution of lymphocyte subsets, cytokine levels, and apoptosis in the spleen.

RESULTS

In comparison to the Ctrl group, the body weight, spleen index, peripheral blood cell, and splenocyte quantities decreased significantly after exposure, accompanied by a notable increase of apoptosis in spleen cells. Moreover, ionizing radiation also broke the balance of CD4+/CD8+, Th1/Th2, and Th17/Treg, triggering immune imbalance and immunosuppression. The above injuries occurred on the 1^st day after exposure, worsened on the 3^rd, and were relieved on the 7^th day. However, the pretreatment of YQJD decoction increased the spleen index, improved the spleen structure, and inhibited radiation-induced apoptosis after exposure. Additionally, YQJD decoction has shown its ability to promote immunological balance recovery following exposure by regulating CD4+/CD8+, Th1/Th2, and Th17/Treg ratios, which may minimize the risk of infection. In addition, the high-dose of YQJD decoction showed a better protective effect than the low-dose group.

CONCLUSION

The protective effects of YQJD decoction on 2 Gy ⁶⁰Coγray induced spleen injury were confirmed in this study. This mechanism may be related to inhibiting apoptosis and modulating immune balance. This exploration might provide new insights into the use of Chinese herbs on radioprotection of the immune system.

Expansion of monocytic myeloid-derived suppressor cells ameliorated intestinal inflammatory response by radiation through SOCS3 expression

Radiation-induced colitis is a common clinical problem after radiation therapy and accidental radiation exposure. Myeloid-derived suppressor cells (MDSCs) have immunosuppressive functions that use a variety of mechanisms to alter both the innate and the adaptive immune systems. Here, we demonstrated that radiation exposure in mice promoted the expansion of splenic and intestinal MDSCs and caused intestinal inflammation due to the increased secretion of cytokines. Depletion of monocytic MDSCs using anti-Ly6C exacerbated radiation-induced colitis and altered the expression of inflammatory cytokine IL10. Adoptive transfers of 0.5 Gy-derived MDSCs ameliorated this radiation-induced colitis through the production IL10 and activation of both STAT3 and SOCS3 signaling. Intestinal-inflammation recovery using 0.5 Gy-induced MDSCs was assessed using histological grading of colitis, colon length, body weight, and survival rate. Using in vitro co-cultures, we found that 0.5 Gy-induced MDSCs had higher expression levels of IL10 and SOCS3 compared with 5 Gy-induced MDSCs. In addition, IL10 expression was not enhanced in SOCS3-depleted cells, even in the presence of 0.5 Gy-induced monocytic MDSCs. Collectively, the results indicate that 0.5 Gy-induced MDSCs play an important immunoregulatory role in this radiation-induced colitis mouse model by releasing anti-inflammatory cytokines and suggest that IL10-overexpressing mMDSCs may be potential immune-therapy targets for treating colitis.

Effects of Chronic Low-Dose Internal Radiation on Immune-Stimulatory Responses in Mice

The Linear-No-Threshold (LNT) model predicts a dose-dependent linear increase in cancer risk. This has been supported by biological and epidemiological studies at high-dose exposures. However, at low-doses (LDR ≤ 0.1 Gy), the effects are more elusive and demonstrate a deviation from linearity. In this study, the effects of LDR on the development and progression of mammary cancer in FVB/N-Tg(MMTVneu)202Mul/J mice were investigated. Animals were chronically exposed to total doses of 10, 100, and 2000 mGy via tritiated drinking water, and were assessed at 3.5, 6, and 8 months of age. Results indicated an increased proportion of NK cells in various organs of LDR exposed mice. LDR significantly influenced NK and T cell function and activation, despite diminishing cell proliferation. Notably, the expression of NKG2D receptor on NK cells was dramatically reduced at 3.5 months but was upregulated at later time-points, while the expression of NKG2D ligand followed the opposite trend, with an increase at 3.5 months and a decrease thereafter. No noticeable impact was observed on mammary cancer development, as measured by tumor load. Our results demonstrated that LDR significantly influenced the proportion, proliferation, activation, and function of immune cells. Importantly, to the best of our knowledge, this is the first report demonstrating that LDR modulates the cross-talk between the NKG2D receptor and its ligands.