The TRPM2 Ion Channel Regulates Inflammatory Functions of Neutrophils During Listeria monocytogenes Infection

Abstract

During infection, phagocytic cells pursue homeostasis in the host via multiple mechanisms that control microbial invasion. Neutrophils respond to infection by exerting a variety of cellular processes, including chemotaxis, activation, phagocytosis, degranulation and the generation of reactive oxygen species (ROS). Calcium (Ca 2+ ) signaling and the activation of specific Ca 2+ channels are required for most antimicrobial effector functions of neutrophils. The transient receptor potential melastatin-2 (TRPM2) cation channel has been proposed to play important roles in modulating Ca 2+ mobilization and oxidative stress in neutrophils. In the present study, we use a mouse model of Listeria monocytogenes infection to define the role of TRPM2 in the regulation of neutrophils' functions during infection. We show that the susceptibility of Trpm2 −/− mice to L. monocytogenes infection is characterized by increased migration rates of neutrophils and monocytes to the liver and spleen in the first 24 h. During the acute phase of L. monocytogenes infection, Trpm2 −/− mice developed septic shock, characterized by increased serum levels of TNF-α, IL-6, and IL-10. Furthermore, in vivo depletion of neutrophils demonstrated a critical role of these immune cells in regulating acute inflammation in Trpm2 −/− infected mice. Gene expression and inflammatory cytokine analyses of infected tissues further confirmed the hyperinflammatory profile of Trpm2 −/− neutrophils. Finally, the increased inflammatory properties of Trpm2 −/− neutrophils correlated with the dysregulated cytoplasmic concentration of Ca 2+ and potentiated membrane depolarization, in response to L. monocytogenes. In conclusion, our findings suggest that the TRPM2 channel plays critical functional roles in regulating the inflammatory properties of neutrophils and preventing tissue damage during Listeria infection.

Z-form extracellular DNA is a structural component of the bacterial biofilm matrix

“…To test this hypothesis, we incubated neutrophils with DNase, HU NTHI , CbpA, or buffer for 4 h with NTHI (16 h after seeding where the bacteria are in equilibrium between residence in the young biofilm and the planktonic state due to natural biofilm remodeling). Triton X-100 was added to lyse neutrophils to enable recovery of viable intracellular bacteria, and total CFU NTHI were enumerated for each condition to measure the relative percent bacterial killing within the system attributable to PMN NETosis (Robledo-Avila et al, 2020). As shown in Figure 5C, addition of either DNase or HU resulted in a marked reduction of measurable bacterial killing by NETs as compared to media control or CbpA.…”

Ion and Water Transport in Neutrophil Granulocytes and Its Impairment during Sepsis

“…TRPM2, a Ca 2+ permeable, non-selective cation channel, which is activated by ADPr, temperature, oxidative stress, and Ca 2+ [ 159 ], has been proposed to play important roles in modulating Ca 2+ mobilization and oxidative stress in neutrophils. For example, during experimental sepsis in mice infected with Listeria monocytogenes, the TRPM2 cation channel modulated membrane depolarization, Ca 2+ mobilization, and subsequent ROS generation [ 160 ]. In this study, a lack of TRPM2 resulted in reduced sepsis survival, and in neutrophils led to enhanced depolarization, dysregulation of intracellular Ca 2+ , and aggravated oxidative burst, all of which might be harmful to the host [ 160 ].…”

“…For example, during experimental sepsis in mice infected with Listeria monocytogenes, the TRPM2 cation channel modulated membrane depolarization, Ca 2+ mobilization, and subsequent ROS generation [ 160 ]. In this study, a lack of TRPM2 resulted in reduced sepsis survival, and in neutrophils led to enhanced depolarization, dysregulation of intracellular Ca 2+ , and aggravated oxidative burst, all of which might be harmful to the host [ 160 ]. Another mechanism involves the ATP-gated purinoceptor P2X1 ion channel, which with its relatively high Ca 2+ permeability could limit the oxidative burst response during LPS-induced murine sepsis [ 161 ].…”

“…Such a phenomenon could explain, in part, such a discrepancy between the studies [ 182 ]. Activation of the TRPM2 channel reduced the NET formation, and cell death in neutrophils in a model of Listeria monocytogenes infection [ 160 ]. Interestingly, a HCO 3 − -mediated alkalization of neutrophils favored spontaneous and LPS-induced NETosis, possibly because of modulation of intracellular Ca 2+ [ 84 ].…”

Does Cyclic ADP-Ribose (cADPR) Activate the Non-selective Cation Channel TRPM2?

“…TRPM2 is a non-selective, Ca 2+ -permeable cation channel expressed in immune cells like monocytes ( 1 , 2 ), macrophages ( 3 – 5 ), neutrophils ( 6 – 9 ), dendritic cells ( 10 ) and effector T cells ( 11 ). The channel plays a role in the inflammatory response by modulating differentiation ( 10 ), cell migration and chemotaxis ( 7 , 10 , 12 ), cytokine ( 11 ) and chemokine secretion ( 1 ) and is regulated in a complex manner integrating inputs from the physical environment of the cell like temperature ( 13 ) and pH ( 14 ) with intracellular second messengers like Ca 2+ ( 15 , 16 ) and adenine nucleotides.…”