Hyperbaric oxygen therapy increases telomere length and decreases immunosenescence in isolated blood cells: a prospective trial

 I don't necessarily trust this since it was done by Shai Efrati. Shai Efrati has conflicts, he is the director of the Hyperbaric Oxygen Institute at the Assaf Harofeh Medical Center.

Hyperbaric oxygen therapy increases telomere length and decreases immunosenescence in isolated blood cells: a prospective trial

Yafit Hachmo^{1, *} , Amir Hadanny^{2,3,4, *} , Ramzia Abu Hamed¹ , Malka Daniel-Kotovsky² , Merav Catalogna² , Gregory Fishlev² , Erez Lang² , Nir Polak² , Keren Doenyas² , Mony Friedman² , Yonatan Zemel² , Yair Bechor² , Shai Efrati^1,2,3,5

• ¹ Research and Development Unit, Shamir Medical Center, Zerifin, Israel
• ² The Sagol Center for Hyperbaric Medicine and Research, Shamir (Assaf-Harofeh) Medical Center, Zerifin, Israel
• ³ Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
• ⁴ Bar Ilan University, Ramat-Gan, Israel
• ⁵ Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv, Israel

* Equal contribution

Received: September 3, 2020       Accepted: October 22, 2020       Published: November 18, 2020

https://doi.org/10.18632/aging.202188
How to Cite

Copyright: © 2020 Yafit et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

Introduction:  

Aging is characterized by the progressive loss of physiological capacity. At the cellular level, two key hallmarks of the aging process include telomere length (TL) shortening and cellular senescence. Repeated intermittent hyperoxic exposures, using certain hyperbaric oxygen therapy (HBOT) protocols, can induce regenerative effects which normally occur during hypoxia. The aim of the current study was to evaluate whether HBOT affects TL and senescent cell concentrations in a normal, non-pathological, aging adult population.

Methods: 

Thirty-five healthy independently living adults, aged 64 and older, were enrolled to receive 60 daily HBOT exposures. Whole blood samples were collected at baseline, at the 30^th and 60^th session, and 1-2 weeks following the last HBOT session. Peripheral blood mononuclear cells (PBMCs) telomeres length and senescence were assessed.

Results: 

Telomeres length of T helper, T cytotoxic, natural killer and B cells increased significantly by over 20% following HBOT. The most significant change was noticed in B cells which increased at the 30^th session, 60^th session and post HBOT by 25.68%±40.42 (p=0.007), 29.39%±23.39 (p=0.0001) and 37.63%±52.73 (p=0.007), respectively.

There was a significant decrease in the number of senescent T helpers by -37.30%±33.04 post-HBOT (P<0.0001). T-cytotoxic senescent cell percentages decreased significantly by -10.96%±12.59 (p=0.0004) post-HBOT.

In conclusion, the study indicates that HBOT may induce significant senolytic effects including significantly increasing telomere length and clearance of senescent cells in the aging populations.

Introduction

Aging can be characterized by the progressive loss of physiological integrity, resulting in impaired functions and susceptibility for diseases and death. This biological deterioration is considered a major risk factor for cancer, cardiovascular diseases, diabetes and Alzheimer’s disease among others. At the cellular level, there are two key hallmarks of the aging process: shortening of telomere length and cellular senescence [1].

Telomeres are tandem nucleotide repeats located at the end of the chromosomes which maintain genomic stability. Telomeres shorten during replication (mitosis) due to the inherent inability to fully replicate the end part of the lagging DNA strand [2]. Telomere length (TL), measuring between 4 to 15 kilobases, gradually shorten by ~20-40 bases per year and is associated with different diseases, low physical performance and cortical thinning of the brain [3–5]. When TL reaches a critical length, cells cannot replicate and progress to senescence or programmed cell death [6]. Goglin et al. demonstrated that adults with shorter TLs have increased mortality rates [7]. Shortened TLs can be a direct inherited trait, but several environmental factors have also been associated with shortening TL including stress, lack of physical endurance activity, excess body mass index, smoking, chronic inflammation, vitamins deficiency and oxidative stress [2, 8, 9].

Cellular senescence is an arrest of the cell cycle which can be caused by telomere shortening [10], as well as other aging associated stimuli independent of TL such as non-telomeric DNA damage [1]. The primary purpose of senescence is to prevent propagation of damaged cells by triggering their elimination via the immune system. The accumulation of senescent cells with aging reflects either an increase in the generation of these cells and/or a decrease in their clearance, which in turn aggravates the damage and contributes to aging [1].

A growing body of research has found several pharmacological agents that can reduce the telomere shortening rate [11, 12]. Several lifestyle interventions including endurance training, diets and supplements targeting cell metabolism and oxidative stress have reported relatively small effects (2-5%) on TL^3, [2, 8, 9].

Hyperbaric oxygen therapy (HBOT) utilizes 100% oxygen in an environmental pressure higher than one absolute atmospheres (ATA) to enhance the amount of oxygen dissolved in body’s tissues. Repeated intermittent hyperoxic exposures, using certain HBOT protocols, can induce physiological effects which normally occur during hypoxia in a hyperoxic environment, the so called hyperoxic-hypoxic paradox [13–16]. In addition, it was recently demonstrated that HBOT can induce cognitive enhancements in healthy aging adults via mechanisms involving regional changes in cerebral blood flow [17]. On the cellular level, it was demonstrated that HBOT can induce the expression of hypoxia induced factor (HIF), vascular endothelial growth factor (VEGF) and sirtuin (SIRT), stem cell proliferation, mitochondrial biogenesis, angiogenesis and neurogenesis [18]. However, no study to date has examined HBOT’s effects on TL and senescent cell accumulation.

The aim of the current study was to evaluate whether HBOT affects TL and senescence-like T-cells population in aging adults.

Results

Thirty-five individuals were assigned to HBOT. Five patients did not complete baseline assessments and were excluded. All 30 patients who completed baseline evaluations completed the interventions. Due to the low quality of blood samples (low number of cells or technician error), four patients were excluded from the telomere analysis and 10 patients from senescent cell analysis (Figure 1). The baseline characteristics and comparison of the cohorts following exclusion of the patients are provided in Table 1. There were no significant differences between the three groups (Table 1).

Figure 1. Patient flowchart.

Table 1. Baseline characteristics.

		HBOT	Telomere analysis	Senescent analysis	P-value
N		30	25 (83.3%)	20 (66.6%)
Age (years)		68.41±13.2	67.56±14.35	66.70±16.00	0.917
BMI		26.77±3.20	26.89±3.34	27.14±3.81	0.946
Males		16 (53.3%)	13 (52.0%)	10 (50.0%)	0.987
Females		14 (47.7%)	12 (48.0%)	10 (50.0%)	0.987
Complete blood count
	Hemoglobin	6.33±1.25	6.57±1.15	6.58±1.29	0.707
	White blood cells	14.02±1.40	13.92±1.35	13.97±1.49	0.969
	%PBMC	39.96±6.75	39.25±6.64	38.59±6.63	0.774
	Platelets	239.87±1.39	244.08±43.0	254.05±41.4	0.559
Chronic medical conditions
	Atrial fibrillation	4 (13.3%)	4 (16.0%)	2 (10.0%)	0.841
	Hypothyroidism	4 (13.3%)	4 (16.0%)	3 (15.8%)	0.956
	Obstructive sleep apnea	4 (13.3%)	4 (16.0%)	3 (15.0%)	0.961
	Asthma	1 (3.3%)	1 (4.0%)	0	0.680
	BPH	7 (23.3%)	5 (20.0%)	6 (30.0%)	0.733
	GERD	3 (10%)	2 (8.0%)	2 (10.0%)	0.961
	Osteoporosis	5 (16.7%)	5 (20.0%)	4 (20.0%)	0.936
	Rheumatic arthritis	1 (3.3%)	0	1 (5.0%)	0.561
	Osteoarthritis	7 (23.3%)	4 (16.0%)	5 (25.0%)	0.755
	Diabetes mellitus	3 (10%)	3 (12.0%)	2 (10.0%)	0.966
	Hypertension	7 (23.3%)	5 (20.0%)	5 (25.0%)	0.918
	Dyslipidemia	16 (53.3%)	14 (56.0%)	12 (60.0%)	0.897
	Ischemic heart disease	2 (6.7%)	1 (4.0%)	2 (10.0%)	0.725
	History of smoking	10 (33.3%)	8 (32.0%)	7 (35.0%)	0.978
Chronic medications
	Anti-aggregation	8 (26.7%)	6 (24.0%)	5 (25.0%)	0.974
	ACE-Inhibitors/ARB blockers	6 (20%)	6 (24.0%)	6 (30.0%)	0.720
	Beta blockers	5 (16.7%)	5 (20.0%)	3 (15.0%)	0.901
	Calcium blockers	3 (10%)	3 (12.0%)	2 (10.0%)	0.966
	Alpha blockers	7 (23.3%)	5 (20.0%)	6 (30.0%)	0.733
	Diuretics	2 (6.7%)	1 (4.0%)	1 (5.0%)	0.906
	Statins	10 (33.3%)	9 (36.0%)	7 (35.0%)	0.978
	Oral hypoglycemic	1 (3.3%)	1 (4.0%)	1 (5.0%)	0.958
	Bisphosphonates	1 (3.3%)	1 (4.0%)	1 (5.0%)	0.958
	Proton pump inhibitors	3 (10%)	3 (12.0%)	3 (15.0%)	0.726
	Hormones	3 (10%)	3 (12.0%)	2 (10.0%)	0.966
	Benzodiazepines	3 (10%)	2 (8.0%)	1 (5.0%)	0.816
	SSRI	5 (16.7%)	5 (20.0%)	3 (15.0%)	0.990

Telomere length

Compared to the baseline, the T-helper telomere lengths were significantly increased at the 30^th session and post-HBOT by 21.70±40.05 (p=0.042), 23.69%±39.54 (p=0.012) and 29.30±38.51 (p=0.005), respectively (Figure 2). However, repeated measures analysis shows a non-significant trend (F=4.663, p=0.06, Table 2 and Figure 2).

Figure 2. Telomere length changes with HBOT. Mean+SEM *p<0.05, **p<0.01, ***p<0.001.

Table 2. Telomere length and senescent cell changes post-HBOT.

		Absolute changes				Relative changes (%)			Repeated measures F (p)
PBMC	Baseline	30th Session		60th Session	Post HBOT	30th session	60th session	Post-HBOT
PBMC ((N=25)	2.55±0.53				-0.15±0.40			-4.91±16.70	1.987 (t) 0.09
PBMC (N=20)	2.50±0.53				-0.13±0.31			-4.21±11.99	1.810 (t) 0.07
Relative telomeres length (N=25)
Natural killer	9.27±1.91	11.77±5.14 (0.045)		10.73±2.73 (0.013)	11.75±4.22 (0.06)	25.02±51.42	20.56±33.35	22.16±44.81	0.812 (0.391)
B-cells	8.36±2.02	10.22±3.04 (0.007)		11.23±3.58 (0.0001)	11.17±2.98 (0.007)	25.68±40.42	29.39±23.39	37.63±52.73	7.390 (0.017)
T Helper	8.04±1.82	9.92±3.68 (0.042)		9.63±2.17 (0.012)	10.20±2.77 (0.005)	21.70±40.05	23.69±39.54	29.30±38.51	4.663 (0.063)
T Cytotoxic	8.26±1.54	9.83±4.08 (0.11)		10.08±3.33 (0.019)	10.15±2.74 (0.023)	18.29±45.62	24.13±40.88	19.59±33.98	1.159 (0.310)
Senescent cells (% of T cells) (N=20)
T Helper	10.29±5.42	7.84±7.09 (0.09)		8.51±7.45 (0.20)	6.22±4.88 (<0.0001)	-19.66±80.03	-11.67±94.30	-37.30±33.04	8.548 (0.01)
T Cytotoxic	52.19±21.07	45.53±19.91 (<0.0001)		45.45±18.81 (0.002)	46.59±21.91 (0.0004)	-12.21±8.74	-9.81±9.50	-10.96±12.59	6.916 (0.018)
P-values shown in () compared to baseline.
P-values in bold <0.05.

Compared to baseline, telomere lengths of B cells increased significantly at the 30^th session, 60^th session and post-HBOT by 25.68%±40.42 (p=0.007), 29.39%±23.39 (p=0.0001) and 37.63%±52.73 (p=0.007), respectively (Figure 2). Repeated measures analysis shows a significant within-group effect (F=0.390, p=0.017, Table 2 and Figure 2).

Compared to baseline, natural killer cells telomer lengths significantly increased at the 30^th session (p=0.045) and at the 60^th session by 20.56% ±33.35 (p=0.013). Post-HBOT, telomere lengths increased by 22.16%±44.81 post-HBOT (p=0.06, Table 2 and Figure 2). Repeated measures analysis indicates that there was no additional significant effect after the 30^th session (F=0.812, p=0.391).

Compared to baseline, cytotoxic T-cells had a non-significant increase at the 30^th session by 18.29%±45.62 (p=0.11), followed by a significant increase of 24.13%±40.88 at the 60^th session (p=0.0019) and 19.59%±33.98 post-HBOT (p=0.023). Repeated measures analysis indicates that there was no additional significant effect after the 30^th session (F=1.159, p=0.310, Table 2 and Figure 2).

Senescent cells

There was a non-significant decrease in the number of senescent T-helpers at the 30^th session and 60^th session by -19.66%±80.03 (p=0.09) and -11.67%±94.30 (p=0.20) respectively. However, there was a significant drop in the number of senescent T helpers by -37.30%±33.04 post-HBOT (P<0.0001, Figure 3). Repeated measures analysis showed a significant continuous effect even after the 30^th session, with a within-group effect (F=8.547, p=0.01, Table 2 and Figure 3).