TY - JOUR
T1 - Transient nutrient deprivation promotes macropinocytosisdependent intracellular bacterial community development
AU - Hardison, Rachael L.
AU - Heimlich, Derek R.
AU - Harrison, Alistair
AU - Beatty, Wandy L.
AU - Rains, Sarah
AU - Moseley, M. Arthur
AU - Thompson, J. Will
AU - Justice, Sheryl S.
AU - Masona, Kevin M.
N1 - Funding Information:
This work was supported by NIH R01 DC013313 (K.M.M. and S.S.J.), the Ohio State University Infectious Disease Institute (R.L.H.), and the Research Institute Trainee Association Stipend Award at the Research Institute at Nationwide Children’s Hospital (R.L.H.).
Funding Information:
This work was supported by NIH R01 DC013313 (K.M.M. and S.S.J.), the Ohio State University Infectious Disease Institute (R.L.H.), and the Research Institute Trainee Association Stipend Award at the Research Institute at Nationwide Children's Hospital (R.L.H.). We acknowledge Alice Lo for technical assistance. We also acknowledge Jennifer Edwards for assistance with intracellular survival assay protocols and helpful discussions.
Publisher Copyright:
© 2018 Hardison et al.
PY - 2018/9/1
Y1 - 2018/9/1
N2 - Nutrient limitation restricts bacterial growth in privileged sites such as the middle ear. Transient heme-iron restriction of nontypeable Haemophilus influenzae (NTHI), the major causative agent of chronic and recurrent otitis media (OM), promotes new and diverse phenotypes that can influence planktonic, biofilm, and intracellular lifestyles of NTHI. However, the bacterial responses to nutrient restriction that impact intracellular fate and survival of NTHI are unknown. In this work, we provide evidence for the role of transient heme-iron restriction in promoting the formation of intracellular bacterial communities (IBCs) of NTHI both in vitro and in vivo in a preclinical model of OM. We show that transient heme-iron restriction of NTHI results in significantly increased invasion and intracellular populations that escape or evade the endolysosomal pathway for increased intracellular survival. In contrast, NTHI continuously exposed to heme-iron traffics through the endolysosomal pathway for degradation. The use of pharmacological inhibitors revealed that prior heme-iron status does not appear to influence NTHI internalization through endocytic pathways. However, inhibition of macropinocytosis altered the intracellular fate of transiently restricted NTHI for degradation in the endolysosomal pathway. Furthermore, prevention of macropinocytosis significantly reduced the number of IBCs in cultured middle ear epithelial cells, providing evidence for the feasibility of this approach to reduce OM persistence. These results reveal that microenvironmental cues can influence the intracellular fate of NTHI, leading to new mechanisms for survival during disease progression.
AB - Nutrient limitation restricts bacterial growth in privileged sites such as the middle ear. Transient heme-iron restriction of nontypeable Haemophilus influenzae (NTHI), the major causative agent of chronic and recurrent otitis media (OM), promotes new and diverse phenotypes that can influence planktonic, biofilm, and intracellular lifestyles of NTHI. However, the bacterial responses to nutrient restriction that impact intracellular fate and survival of NTHI are unknown. In this work, we provide evidence for the role of transient heme-iron restriction in promoting the formation of intracellular bacterial communities (IBCs) of NTHI both in vitro and in vivo in a preclinical model of OM. We show that transient heme-iron restriction of NTHI results in significantly increased invasion and intracellular populations that escape or evade the endolysosomal pathway for increased intracellular survival. In contrast, NTHI continuously exposed to heme-iron traffics through the endolysosomal pathway for degradation. The use of pharmacological inhibitors revealed that prior heme-iron status does not appear to influence NTHI internalization through endocytic pathways. However, inhibition of macropinocytosis altered the intracellular fate of transiently restricted NTHI for degradation in the endolysosomal pathway. Furthermore, prevention of macropinocytosis significantly reduced the number of IBCs in cultured middle ear epithelial cells, providing evidence for the feasibility of this approach to reduce OM persistence. These results reveal that microenvironmental cues can influence the intracellular fate of NTHI, leading to new mechanisms for survival during disease progression.
KW - Endolysosomal pathway
KW - Haemophilus
KW - Host cell invasion
KW - Intracellular bacterial community
KW - Macropinocytosis
KW - NTHI
KW - Nutritional immunity
UR - http://www.scopus.com/inward/record.url?scp=85055071639&partnerID=8YFLogxK
U2 - 10.1128/mSphere.00286-18
DO - 10.1128/mSphere.00286-18
M3 - Article
C2 - 30209128
AN - SCOPUS:85055071639
VL - 3
JO - mSphere
JF - mSphere
SN - 2379-5042
IS - 5
M1 - e00286-18
ER -