Clofazimine Crystals in the Cytoplasm of Pulmonary Macrophages

Harbeck, R J; Worthen, G. Scott; Lebo, T D; Peloquin, Charles A

doi:10.1345/aph.18170

Cited by 12 publications

(18 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our results provide evidence that a solution-to-solid phase transition, more specifically the formation and stabilization of an intracellular, crystalline hydrochloride salt form of the drug, is responsible for the high tissue-to-serum partition coefficients of CFZ in spleen and liver. Such massive sequestration of CFZ as crystal-like drug inclusions (CLDIs) in the macrophages of spleen 10 , liver 22 and intestines 37 as well as lung 8 has been reported in humans. In previous studies, we and others have shown that CLDIs originate from a multi-lamellar, membrane-bound perinuclear cytoplasmic structure, with morphological characteristics resembling autophagosomes derived from degenerating lysosomes, mitochondria and perhaps other organelles 8,12,24,26,31,38,39 .…”

Section: Discussionmentioning

confidence: 87%

“…While searching for drugs exhibiting natural, intracellular drug bioaccumulation mechanisms, clofazimine (CFZ) caught our attention 8–12 . CFZ is an FDA-approved riminophenazine antibiotic (Figure 1) that has been remarkably effective against mycobacterial infections such as leprosy 13–15 and mycobacterium avium infections in AIDS patients 16,17 .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Chemical Analysis of Drug Biocrystals: A Role for Counterion Transport Pathways in Intracellular Drug Disposition

et al. 2015

View full text Add to dashboard Cite

In mammals, highly lipophilic small molecule chemical agents can accumulate as inclusions within resident tissue macrophages. In this context, we characterized the biodistribution, chemical composition and structure of crystal-like drug inclusions (CLDIs) formed by clofazimine (CFZ), a weakly basic lipophilic drug. With prolonged oral dosing, CFZ exhibited a significant partitioning with respect to serum and fat due to massive bioaccumulation and crystallization in the liver and spleen. The NMR, Raman and Powder X-ray diffraction (p-XRD) spectra of CLDIs isolated from the spleens of CFZ-treated mice matched the spectra of pure, CFZ hydrochloride crystals (CFZ-HCl). Elemental analysis revealed a 237-fold increase in chlorine content in CLDIs compared to untreated tissue samples, and a five-fold increase in chlorine content compared to CFZ-HCl, suggesting that the formation of CLDIs occurs through a chloride mediated crystallization mechanism. Single crystal analysis revealed that CFZ-HCl crystals had a densely-packed orthorhombic lattice configuration. In vitro, CFZ-HCl formed at a pH of 4–5 only if chloride ions were present at sufficiently high concentrations (>50:1 Cl−:CFZ), indicating that intracellular chloride transport mechanisms play a key role in the formation of CLDIs. While microscopy and pharmacokinetic analyses clearly revealed crystallization and intracellular accumulation of the drug in vivo, the chemical and structural characterization of CLDIs implicates a concentrative, chloride transport mechanism, paralleling and thermodynamically stabilizing, the massive bioaccumulation of a weakly basic drug.

show abstract

Section: Discussionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Chemical Analysis of Drug Biocrystals: A Role for Counterion Transport Pathways in Intracellular Drug Disposition

et al. 2015

View full text Add to dashboard Cite

show abstract

“…In previous studies, it has been shown that following prolonged oral administration of CFZ, the drug massively bioaccumulates as intracellular biocrystals in resident tissue macrophages (8)(9)(10)(11)(12). Therefore, it is natural to assume that this bioaccumulation phenomenon contributes to the drug's toxicity, whereas the soluble form of CFZ, which circulates and partitions to and from the different organs, is responsible for CFZ's mechanism of action.…”

mentioning

confidence: 99%

Clofazimine Biocrystal Accumulation in Macrophages Upregulates Interleukin 1 Receptor Antagonist Production To Induce a Systemic Anti-Inflammatory State

Yoon

Keswani

Sud

et al. 2016

Antimicrob Agents Chemother

View full text Add to dashboard Cite

Clofazimine (CFZ) is a poorly soluble antibiotic and anti-inflammatory drug indicated for the treatment of leprosy. In spite of its therapeutic value, CFZ therapy is accompanied by the formation of drug biocrystals that accumulate within resident tissue macrophages, without obvious toxicological manifestations. Therefore, to specifically elucidate the off-target consequences of drug bioaccumulation in macrophages, we compared the level of inflammasome activation in CFZ-accumulating organs (spleen, liver and lung) in mice after 2 and 8 weeks of CFZ treatment when the drug exists in soluble and insoluble (biocrystalline) forms, respectively. Surprisingly, the results showed a drastic reduction in caspase 1 and interleukin-1␤ (IL-1␤) cleavage in the livers of mice treated with CFZ for 8 weeks (8-week-CFZ-treated mice) compared to 2-week-CFZ-treated and control mice, which was accompanied by a 3-fold increase in hepatic IL-1 receptor antagonist (IL-1RA) production and a 21-fold increase in serum IL-1RA levels. In the lung and spleen, IL-1␤ cleavage and tumor necrosis factor alpha expression were unaffected by soluble or biocrystal CFZ forms. Functionally, there was a drastic reduction of carrageenan-and lipopolysaccharide-induced inflammation in the footpads and lungs, respectively, of 8-week-CFZ-treated mice. This immunomodulatory activity of CFZ biocrystal accumulation was attributable to the upregulation of IL-1RA, since CFZ accumulation had minimal effect in IL-1RA knockout mice or 2-week-CFZ-treated mice. In conclusion, CFZ accumulation and biocrystal formation in resident tissue macrophages profoundly altered the host's immune system and prompted an IL-1RA-dependent, systemic anti-inflammatory response.

show abstract

“…Accumulation of drugs to levels that are directly bactericidal is only one possible mode of action. Physical accumulation is, however, well supported by observations regarding clofazimine in the clinical literature (31)(32)(33)(34), wherein crystals of drug have been observed in lung tissue of treated patients. Interest in clofazimine has recently intensified due to its successful use against multidrugresistant M. tuberculosis (35,36) and the demonstration that it can shorten treatment in a murine model of TB (37).…”

Section: Discussionmentioning

confidence: 69%

Subcellular Partitioning and Intramacrophage Selectivity of Antimicrobial Compounds against Mycobacterium tuberculosis

Schump

et al. 2017

Antimicrob Agents Chemother

View full text Add to dashboard Cite

The efficacy of antimicrobial drugs against Mycobacterium tuberculosis, an intracellular bacterial pathogen, is generally first established by testing compounds against bacteria in axenic culture. However, inside infected macrophages, bacteria encounter an environment which differs substantially from broth culture and are subject to important host-dependent pharmacokinetic phenomena which modulate drug activity. Here, we describe how pH-dependent partitioning drives asymmetric antimicrobial drug distribution in M. tuberculosis-infected macrophages. Specifically, weak bases with moderate activity against M. tuberculosis (fluoxetine, sertraline, and dibucaine) were shown to accumulate intracellularly due to differential permeability and relative abundance of their ionized and nonionized forms. Nonprotonatable analogs of the test compounds did not show this effect. Neutralization of acidic organelles directly with ammonium chloride or indirectly with bafilomycin A1 partially abrogated the growth restriction of these drugs. Using high-performance liquid chromatography, we quantified the degree of accumulation and reversibility upon acidic compartment neutralization in macrophages and observed that accumulation was greater in infected than in uninfected macrophages. We further demonstrate that the efficacy of a clinically used compound, clofazimine, is augmented by pH-based partitioning in a macrophage infection model. Because the parameters which govern this effect are well understood and are amenable to chemical modification, this knowledge may enable the rational development of more effective antibiotics against tuberculosis.

show abstract

Clofazimine Crystals in the Cytoplasm of Pulmonary Macrophages

Cited by 12 publications

References 0 publications

Chemical Analysis of Drug Biocrystals: A Role for Counterion Transport Pathways in Intracellular Drug Disposition

Chemical Analysis of Drug Biocrystals: A Role for Counterion Transport Pathways in Intracellular Drug Disposition

Clofazimine Biocrystal Accumulation in Macrophages Upregulates Interleukin 1 Receptor Antagonist Production To Induce a Systemic Anti-Inflammatory State

Subcellular Partitioning and Intramacrophage Selectivity of Antimicrobial Compounds against Mycobacterium tuberculosis

Contact Info

Product

Resources

About