The Potential Application of Heavy Ion Beams in the Treatment of Arrhythmia: The Role of Radiation-Induced Modulation of Connexin43 and the Sympathetic Nervous System

Biological effects of high-LET irradiation on the circulatory system

PURPOSE

High-linear energy transfer (LET) radiation is generally thought to be more biologically effective in various tissues than low-LET radiation, but whether this also applies to the circulatory system remains unclear. We therefore reviewed biological studies about the effects of high-LET radiation on the circulatory system.

CONCLUSIONS

We identified 76 relevant papers (24 in vitro, 2 ex vivo, 51 in vivo, one overlapping). In vitro studies used human, bovine, porcine or chick vascular endothelial cells or cardiomyocytes, while ex vivo studies used porcine hearts. In vivo studies used mice, rats, rabbits, dogs or pigs. The types of high-LET radiation used were neutrons, α particles, heavy ions and negative pions. Most studies used a single dose, although some investigated fractionation effects. Twenty-one studies estimated the relative biological effectiveness (RBE) that ranged from 0.1 to 130, depending on radiation quality and endpoint. A meta-analysis of 6 in vitro and 8 in vivo studies (selected based on the feasibility of estimating the RBE and its uncertainty) suggested an RBE of 6.69 (95% confidence intervals (CI): 2.51, 10.88) for in vitro studies and 1.14 (95% CI: 0.91, 1.37) for in vivo studies. The meta-analysis of these 14 studies yielded an RBE of 2.88 (95% CI: 1.52, 4.25). This suggests that high-LET radiation is only slightly more effective than low-LET radiation, although substantial inter-study heterogeneity complicates interpretation. Therapeutic effects have also been reported in disease models. Further research is needed to better understand the effects on the cardiovascular system and to improve radiation protection.

Premature senescence and cardiovascular disease following cancer treatments: mechanistic insights

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality, especially among the aging population. The "response-to-injury" model proposed by Dr. Russell Ross in 1999 emphasizes inflammation as a critical factor in atherosclerosis development, with atherosclerotic plaques forming due to endothelial cell (EC) injury, followed by myeloid cell adhesion and invasion into the blood vessel walls. Recent evidence indicates that cancer and its treatments can lead to long-term complications, including CVD. Cellular senescence, a hallmark of aging, is implicated in CVD pathogenesis, particularly in cancer survivors. However, the precise mechanisms linking premature senescence to CVD in cancer survivors remain poorly understood. This article aims to provide mechanistic insights into this association and propose future directions to better comprehend this complex interplay.

Rat Hepatocytes Mitigate Cadmium Toxicity by Forming Annular Gap Junctions and Degrading Them via Endosome-Lysosome Pathway

Gap junction protein connexin 43 (Cx43) plays a critical role in gap junction communication in rat hepatocytes. However, those located between hepatocytes are easily internalized following exposure to poisons. Herein, we investigated the potential of buffalo rat liver 3A (BRL 3A) cells to generate annular gap junctions (AGJs) proficient at alleviating cadmium (Cd) cytotoxic injury through degradation via an endosome-lysosome pathway. Our results showed that Cd-induced damage of liver microtubules promoted Cx43 internalization and increased Cx43 phosphorylation at Ser373 site. Furthermore, we established that Cd induced AGJs generation in BRL 3A cells, and AGJs were subsequently degraded through the endosome-lysosome pathway. Overall, our results suggested that Cx43 internalization and the generation of AGJs were cellular protective mechanisms to alleviate Cd toxicity in rat hepatocytes.

Stereotactic Radiotherapy Ablation and Atrial Fibrillation: Technical Issues and Clinical Expectations Derived From a Systematic Review

Aim

The purpose of this study is to collect available evidence on the feasibility and efficacy of stereotactic arrhythmia radio ablation (STAR), including both photon radiotherapy (XRT) and particle beam therapy (PBT), in the treatment of atrial fibrillation (AF), and to provide cardiologists and radiation oncologists with a practical overview on this topic.

Methods

Three hundred and thirty-five articles were identified up to November 2021 according to preferred reporting items for systematic reviews and meta-analyses criteria; preclinical and clinical studies were included without data restrictions or language limitations. Selected works were analyzed for comparing target selection, treatment plan details, and the accelerator employed, addressing workup modalities, acute and long-term side-effects, and efficacy, defined either by the presence of scar or by the absence of AF recurrence.

Results

Twenty-one works published between 2010 and 2021 were included. Seventeen studies concerned XRT, three PBT, and one involved both. Nine studies (1 in silico and 8 in vivo; doses ranging from 15 to 40 Gy) comprised a total of 59 animals, 12 (8 in silico, 4 in vivo; doses ranging from 16 to 50 Gy) focused on humans, with 9 patients undergoing STAR: average follow-up duration was 5 and 6 months, respectively. Data analysis supported efficacy of the treatment in the preclinical setting, whereas in the context of clinical studies the main favorable finding consisted in the detection of electrical scar in 4/4 patients undergoing specific evaluation; the minimum dose for efficacy was 25 Gy in both humans and animals. No acute complication was recorded; severe side-effects related to the long-term were observed only for very high STAR doses in 2 animals. Significant variability was evidenced among studies in the definition of target volume and doses, and in the management of respiratory and cardiac target motion.

Conclusion

STAR is an innovative non-invasive procedure already applied for experimental treatment of ventricular arrhythmias. Particular attention must be paid to safety, rather than efficacy of STAR, given the benign nature of AF. Uncertainties persist, mainly regarding the definition of the treatment plan and the role of the target motion. In this setting, more information about the toxicity profile of this new approach is compulsory before applying STAR to AF in clinical practice.

Advances of Traditional Chinese Medicine Regulating Connexin43 in the Prevention and Treatment of Myocardial Infarction

Gap junctions are the main form of interaction between cardiomyocytes, through which the electrochemical activities between cardiomyocytes can be synchronized to maintain the normal function of the heart. Connexins are the basis of gap junctions. Changes in the expression, structural changes (e.g., phosphorylation and dephosphorylation), and distribution of connexins can affect the normal electrophysiological activities of the heart. Myocardial infarction (MI) and concurrent arrhythmia, shock, or heart failure can endanger life. The structural and functional damage of connexin (Cx) 43 in cardiomyocytes is a central part of the pathological progression of MI and is one of the main pathological mechanisms of arrhythmia after MI. Therefore, increasing Cx43 expression has become one of the main measures to prevent MI. Also, intervention in Cx43 expression can improve the structural and electrical remodeling of the myocardium to improve MI prognosis. Here, research progress of Cx43 in MI and its prevention and treatment using Traditional Chinese Medicine formulations is reviewed.

Stereotactic radioablation of ventricular arrhythmias in patients with structural heart disease - A systematic review

BACKGROUND AND PURPOSE

Several studies have suggested stereotactic arrhythmia radioablation (STAR) as a treatment option for patients suffering from therapy-refractory ventricular tachycardia or fibrillation (VT/VF).

MATERIAL AND METHODS

We performed a systematic review of human reports of STAR for structural VT/VF to assess its effectivity and safety. All identified publications were assessed for inclusion. This study adheres to the PRISMA guidelines and was registered on PROSPERO (CRD42020183044).

RESULTS

Thirteen studies were included resulting in a population of 57 patients. Median age was 64 (range 34-83), 31 patients (54%) had ischemic cardiomyopathy and 50 patients (88%) had prior catheter ablation (CA) for VT/VF. A mean planned target volume of 64.4 cc (range 3.5-238) with a mean safety margin of 3.3 mm (0-5) was treated with 25 Gy. Immediately following STAR, four patients (7%) experienced an electrical storm. During a mean follow-up duration of 410 days, all patients suffering from sustained VT/VF prior to STAR (n = 55) had a reduction of their sustained VT/VF-burden after STAR, but recurrence occurred in 41 patients (75%) during follow-up. Forty-six patients (81%) had an adverse effect from therapy, but no treatment-related death occurred. Evidence of scar-formation after STAR either by imaging, invasive mapping or histopathology was found in six of nine examined patients (67%).

CONCLUSION

From the still very limited experience, STAR appears effective and safe in patients with structural heart disease and therapy-refractory sustained VT/VF. It is associated with a significant short-term reduction of sustained VT/VF-burden, but recurrences are common.