Macrophage Depletion Reverses Impaired Sympathetic Vasoconstriction and Sensory Vasodilation of Mesenteric Arteries from IL‐10−/− Mice with Inflammatory Bowel Disease
Authors: Grunz‐Borgmann Elizabeth L , Jones Benjamin W , Boerman Erika M 
Published: June 2021

Sympathetic vasoconstriction and sensory vasodilation are impaired in mesenteric arteries (MAs) with Inflammatory Bowel Disease (IBD), but the mechanism is unclear. RNA sequencing of isolated MAs showed altered expression of macrophage (MΦ)‐ and MΦ polarization‐associated genes with IBD. Thus, we predicted that depletion of perivascular MΦ would improve perivascular nerve function. Male and female B6.129P2‐IL10tm1Cgn/J (IL10−/−) mice received H. hepaticus by gastric gavage at 2 and 4d post‐weaning and developed IBD for 90d. Non‐inoculated littermates served as controls. Half each control and IBD group received 2 i.p. injections of clodronate (CLOD, 0.5 and 0.25 mg)‐ or PBS‐containing liposomes 7d apart. Thus 4 groups were assessed: CONT‐PBS, CONT‐CLOD, IBD‐PBS and IBD‐CLOD (N=4–6 mice per group for all experiments). MAs from each group were labeled for M1‐like (CD68) and M2‐like (CD163) MΦ, antigen presenting cells (MHCII), leukocytes (CD45), and perivascular nerves (PGP 9.5) then confocally imaged with 185 × 185 μm2 fields of view (N=16–20 per group). Compared to CONT‐PBS MAs, the adventitia of IBD‐PBS MAs contained significantly more CD163+ (20 vs 6), CD68+ (18 vs 9), MHCII+ (28 vs 13), and CD45+ (28 vs 15) cells. Across groups, immune cells approximate closely with perivascular nerves. Cell counts decreased to <5 cells/field for all markers in both CONT‐CLOD and IBD‐CLOD groups. Vasomotor function was assessed using pressure myography of MAs at 80 cm H2O and 37C. Sympathetic vasoconstriction and sensory inhibition of sympathetic constriction were assessed via electrical field stimulation (EFS, 75V, 2ms, 1–16Hz) ± the sensory blocker capsaicin (10μM). IBD‐PBS MAs exhibited impaired constriction at 8 and 16Hz (max 17% and 34%) compared to CONT‐PBS MAs (max 23% and 42%), which was reversed in IBD‐CLOD MAs (max 27% and 43%). Capsaicin treatment revealed significant sensory inhibition (increased constriction) at 4, 8 and 16Hz in CONT‐PBS and CONT‐CLOD MAs. Capsaicin had no effect in IBD‐PBS MAs, but significant sensory inhibition was restored in IBD‐CLOD MAs. Sensory vasodilation was assessed using the same EFS parameters following sympathetic blockade (guanethidine, 10μM) and preconstriction (phenylephrine, 1 μM). CONT‐PBS and CONT‐CLOD MAs exhibited freq‐dependent sensory dilation (max dilations 70% and 76%, respectively). Dilation was significantly impaired in IBD‐PBS MAs (max 18%) but was restored in IBD‐CLOD MAs (max 63%). Sensory dilation was also measured in the presence of the NOS inhibitor L‐NAME (300 μM), which had little effect on sensory dilation across all groups, despite impaired acetylcholine‐mediated vasodilation in IBD‐PBS MAs that was restored in IBD‐CLOD MAs. Together, these data demonstrate that accumulation of both M1‐ and M2‐like adventitial MΦ during IBD impairs both sympathetic constriction and sensory vasodilation in and endothelial‐independent fashion, with restoration of vasomotor function following clodronate depletion. Targeting MΦ accumulation and/or polarization in the arterial wall may represent a potential treatment to improve perivascular nerve function and therefore tissue perfusion in IBD.Support or Funding InformationR00HL129196This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.