The Effects of Red Light on Mammalian Sperm Rely upon the Color of the Straw and the Medium Used

Abstract

Previous research has determined that irradiation of mammalian sperm with red light increases motility, mitochondrial activity, and fertilization capacity. In spite of this, no study has considered the potential influence of the color of the straw and the extender used. Therefore, this study tests the hypothesis that the response of mammalian sperm to red light is influenced by the color of the straw and the turbidity/composition of the extender. Using the horse as a model, 13 ejaculates from 13 stallions were split into two equal fractions, diluted with Kenney or Equiplus extender, and stored at 4 °C for 24 h. Thereafter, each diluted fraction was split into five equal aliquots and subsequently packed into 0.5-mL straws of red, blue, yellow, white, or transparent color. Straws were either nonirradiated (control) or irradiated with a light–dark–light pattern of 3–3–3 (i.e., light: 3 min, dark: 3 min; light: 3 min) prior to evaluating sperm motility, acrosome and plasma membrane integrity, mitochondrial membrane potential, and intracellular ROS and calcium levels. Our results showed that irradiation increased some motion variables, mitochondrial membrane potential, and intracellular ROS without affecting the integrities of the plasma membrane and acrosome. Remarkably, the extent of those changes varied with the color of the straw and the extender used; the effects of irradiation were more apparent when sperm were diluted with Equiplus extender and packed into red-colored straws or when samples were diluted with Kenney extender and packed into transparent straws. As the increase in sperm motility and intracellular ROS levels was parallel to that of mitochondrial activity, we suggest that the impact of red light on sperm function relies upon the specific rates of energy provided to the mitochondria, which, in turn, vary with the color of the straw and the turbidity/composition of the extender.

Male Infertility and Oxidative Stress: A Focus on the Underlying Mechanisms

“…The wavelength of the light seems be an important element in the cascade of changes that lead to mitochondrial ROS generation. Thus, a brief (<5 min) exposure to red light (620–630 nm) was found to stimulate sperm motility and ROS generation by equine and, to a much less extent, ram spermatozoa [ 98 ]. Similarly, red light (maximum energy at 600 nm) has been found to stimulate ROS generation in populations of human spermatozoa, which responded by exhibiting a burst of hyperactivated motility and associated shifts in intracellular calcium and cAMP [ 99 ].…”

The effects of red LED light on pig sperm function rely upon mitochondrial electron chain activity rather than on a PKC-mediated mechanism

“…Although, under a practical point of view, getting new insights into how light exerts the aforementioned effects could improve in vivo reproductive efficiency, the mechanisms underlying that response remain largely unknown. In addition, previous research has demonstrated that the sperm response to light depends on other factors, including the species, nature of semen (i.e., fresh, frozen-thawed), wavelength range and color of the recipient/straw (Catalán et al, 2020a;Catalán et al, 2020b;Blanco-Prieto et al, 2020;Catalán et al, 2020c;Catalán et al, 2020d;Catalán et al, 2021). In the case of pigs, different studies reported inconsistent results, as whereas Luther et al (2019) found an impairment of sperm function, others observed a positive impact on sperm quality and fertilizing ability (Yeste et al, 2016;Blanco-Prieto et al, 2019;Pezo et al, 2019).…”