Neutrophil labeling with [99mTc]-technetium stannous colloid is complement receptor 3-mediated and increases the neutrophil priming response to lipopolysaccharide

Effects of a stabilized stannous fluoride dentifrice on clinical, immunomodulatory, and microbial outcomes in a human experimental gingivitis model

BACKGROUND

Stannous fluoride dentifrice is well established for its beneficial clinical effects. In this study, we evaluated the effects of stannous fluoride on inflammation and oral microbiome.

METHODS

In this randomized, parallel-arm, double-blind, controlled clinical trial, we compared clinical resolution of experimental gingivitis by evaluating bleeding on probing, gingival index, and plaque index between stannous fluoride stabilized with zinc phosphate (test) and sodium fluoride (control) dentifrices. Further, these groups were compared for oral neutrophil counts, systemic priming of neutrophils, gingival crevicular fluid (GCF) expression of inflammatory markers, and the oral microbiome.

RESULTS

We found significant reduction in bleeding on probing in the test group compared to the control group in experimental gingivitis when participants used the test dentifrice prior to induction of experimental gingivitis. The test group also showed significant reductions in GCF levels of inflammatory markers (matrix metalloproteinase 8 [MMP8], receptor activator of nuclear factor kappa-Β ligand [RANKL]), oral polymorphonuclear neutrophil (PMN) counts, and systemic neutrophil priming (CD11b expression) during experimental gingivitis. Further, significant reductions in the gram-negative genera Porphyromonas, Tannerella, and Treponema were noted in the test group.

CONCLUSION

The stannous fluoride stabilized with zinc phosphate dentifrice formulation demonstrated clinical reduction in gingival inflammation and a beneficial effect on microbiome and immune markers. This intervention should be explored as a preventive aid in the progression of plaque-induced gingivitis to periodontitis.

Radiosynthesis of (99m)Tc(CO)3-Clinafloxacin Dithiocarbamate and Its Biological Evaluation as a Potential Staphylococcus aureus Infection Radiotracer

BACKGROUND

Clinafloxacin dithiocarbamate (CNND) was radiolabeled with technetium-99m ((99m)Tc) using [(99m)Tc(CO)3(H2O)3](+) and assessed for its radiochemical stability in saline and serum, its in vitro binding with methicillin-resistant Staphylococcus aureus (MRSA) and biodistribution in female nude mice (FNM) artificially infected with live and heat-killed MRSA.

METHODS

In normal saline (NS) the (99m)Tc(CO)3-clinafloxacin dithiocarbamate ((99m)Tc(CO)3-CNND) showed radiochemical stability with a maximum value of 99.10 ± 0.20% and remained stable up to 4 h (92.65 ± 0.18%).

RESULTS

In human serum at 37°C within 16 h of incubation, 14.85% side products as a result of de-tagging developed. Incubation with MRSA gave saturated binding with a maximum value of 72.75 ± 1.20%. Almost six-fold higher uptake was seen in the infected muscle of the FNM as compared to the inflamed and normal muscle. The (99m)Tc(CO)3-CNND complex showed a normal route of excretion from the body of the FNM model.

CONCLUSION

The higher stability in NS, HS, saturated in vitro binding with a live strain of MRSA and six-fold higher uptake in the target organ showed the (99m)Tc(CO)3-CNND complex to be a potential MRSA infection radiotracer.

Examination of trafficking of phagocytosed colloid particles in neutrophils using synchrotron-based X-ray fluorescence microscopy (XFM)

Synchrotron-based X-ray fluorescence microscopy (XFM) can localise chemical elements at a subcellular level. 99mTechnetium stannous (TcSn) colloid is taken up by phagocytes via a Complement Receptor 3 mediated phagocytic process. In the current study, XFM was used to examine the intracellular trafficking of TcSn colloid in neutrophils. XFM was performed on TcSn colloid, and neutrophils labelled with TcSn colloid, in whole blood. We developed a set of pixel by pixel analysis and mapping techniques incorporating cluster analysis that allowed us to differentiate neutrophils and artefactual contaminants, and we examined the changes in element distribution that accompany neutrophil phagocytosis of TcSn colloid. Sn became associated with half the neutrophils. Within cells, Sn colocalised with iron (Fe) and sulphur (S), and was negatively associated with calcium (Ca). Despite the high sensitivity of XFM, Tc was not detected. XFM can help clarify the intracellular processes that accompany neutrophil phagocytosis. The subcellular colocalisation of Sn with Fe is consistent with fusion of the colloid-containing phagosome with neutrophil granules. The association of Sn with S suggests that proteins rich in S-containing amino acids are present in the phagosome. The negative colocalisation with Ca indicates that ongoing maturation of the TcSn colloid phagosome is no longer calcium dependent one hour after phagocytosis.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s10867-011-9233-9) contains supplementary material, which is available to authorized users.

99mTc-Novobiocin: a~novel radiotracer for infection imaging

The radiosynthesis of 99mTc-Novobiocin (99mTc-NBN) complex and its suitability as a radiotracer for infection imaging was assessed. The radiochemical purity (RCP) of the 99mTc-NBN complex was determined using radio-TLC and radioactive HPLC and biodistribution was studied in artificially infected (A.I.) rats and rabbit, using single well gamma counter (SWGRC) interface with scalar count rate meter (SCRM) and Gamma Camera (γ-CM). The maximum RCP observed for the preparation having 2 mg of NBN, 111 MBq of sodium pertechnetate (Na99mTcO4) and 125 μL of SnF2 (1 μg/μL in 0.01 N HCl) at a pH 5.6 was 98.97±0.40% and remained stable >90% up to 120 min. The activity of the 99mTc-NBN in the infected muscle (TI) was significantly increased from 6.50±0.15 to 19.00±0.17% and decreased in the inflamed muscle (TII), normal muscle (NT), blood, liver, spleen, stomach and intestine within 120 min. The TI/NT and TII/NT ratios were 7.60±1.08 and 1.60±1.14. The Whole Body Static (WBS) images of A.I. rabbit were obtained at 30, 40, 50 and 60 min after the I.V. administration of 111 MBq of 99mTc-NBN to the A.I. rabbit. The stability in saline and serum, higher TI/NT, lower TII/NT ratios and WBS images confirmed the feasibility of the 99mTc-NBN complex as an infection imaging agent.

Biodistribution of canine leucocytes labelled with technetium-99m stannous fluoride colloid in whole blood and their ability to localise to sites of induced inflammation

This study assessed the biodistribution of autologous leucocytes radiolabelled with technetium-99m stannous fluoride colloid (99mTcSnC) for detection of foci of induced inflammation in dogs. Venous blood was collected from seven healthy dogs and incubated with 99mTcSnC for 1h at room temperature. Radiolabelled samples were injected intravenously (IV) and the dogs were scanned using a gamma camera. Another seven healthy dogs were injected intradermally with tumour necrosis factor alpha and then IV with 99mTcSnC radiolabelled autologous blood 3h later before being scanned. The radiolabelled leucocytes localised to sites of inflammation by 30 min post-injection. IV injection of autologous leucocytes radiolabelled with 99mTcSnC appears to be a sensitive method for localisation of induced foci of inflammation in dogs.

In whole blood, LPS, TNF-alpha and GM-CSF increase monocyte uptake of 99mtechnetium stannous colloid but do not affect neutrophil uptake

INTRODUCTION

(99m)Technetium stannous colloid (TcSnC) is used in white cell scanning. It labels neutrophils and monocytes via phagocytosis, with uptake mediated by the phagocytic receptor CD11b/CD18 in neutrophils. Uptake of TcSnC is altered by gram-negative infection, possibly due to the endotoxin component lipopolysaccharide (LPS) or to cytokines released during infection (e.g., TNF-alpha and IFN-gamma). Endotoxemia and increased TNF-alpha levels also occur in inflammatory bowel disease. Another potential confounder in cell labeling is that sepsis patients may be treated with GM-CSF and G-CSF, which alter phagocytic cell function. This study aimed to determine how these factors affect TcSnC cellular uptake.

METHODS

Whole blood from six healthy volunteers was incubated with LPS, TNF-alpha, IFN-gamma, GM-CSF or G-CSF. Samples were then mixed with TcSnC. Blood was separated across density gradients and imaged using a gamma camera. Three radioactive count peaks were observed in each tube: free plasma activity, mononuclear cell uptake and neutrophil uptake.

RESULTS

Compared with controls, significant increases in mononuclear cell uptake were induced by LPS, TNF-alpha and GM-CSF stimulation. It was incidentally noted that exogenous estrogens appear to affect TcSnC labeling and may influence the neutrophil response to stimulation. Neutrophil uptake and plasma activity were not significantly affected. IFN-gamma and G-CSF had no significant effect.

CONCLUSIONS

In whole blood, the effect of LPS on TcSnC monocyte uptake is different to its effect on neutrophils, consistent with previously reported differences in CD11b/CD18 expression. TNF-alpha response parallels LPS response. GM-CSF also increases TcSnC uptake by monocytes. These effects should be considered when using TcSnC for imaging purposes, as they will tend to increase monocyte labeling. Estrogens may also affect TcSnC labeling. Responses to IFN-gamma and G-CSF are consistent with previously reported effects of these cytokines on CD11b/CD18 expression.