Stability, Activity, and Application of Topical Doxycycline Formulations in a Diabetic Wound Case Study

INTRODUCTION

Tetracycline molecules comprise a group of broad-spectrum antibiotics whose primary mechanism of action is the inhibition of protein synthesis through the binding of the bacterial ribosome. In addition, tetracyclines inhibit matrix metalloproteases (MMPs), a family of zinc-dependent proteases that contribute to tissue remodeling, inflammation, and angiogenesis and are overexpressed in certain pathophysiologies such as diabetic foot ulcers (DFUs).

OBJECTIVE

This study aims to develop a liquid chromatography and mass spectrometry (LC-MS/MS) doxycycline quantification methodology to facilitate the development of a stable topical doxycycline hyclate (DOXY) formulation as well as evaluate the topical DOXY formulation for the efficacy in MMP-9 inhibition in vitro and in a clinical application of diabetic lower extremity wounds.

MATERIALS AND METHODS

A simple quantification method utilizing LC-MS/MS was used to develop a topical DOXY formulation, a sample of which was analyzed in stability testing. The formulation was evaluated in vitro for MMP-9 activity using a commercial assay and compared with internal kit controls as well as in a clinical setting for wound healing.

RESULTS

Two formulations of 2% (w/w) DOXY demonstrated acceptable stability (±10% target concentration) for 70 days when stored at 4°C. Using an in vitro assay of MMP-9 enzyme activity, the 2% DOXY formulation imparted a ~30% decrease in MMP-9 inhibitory potential as compared with the control drug alone (IC₅₀ values 62.92 µM and 48.27 µM, respectively). This topical product was evaluated for clinical utility in a patient with a DFU, and preliminary data suggest this intervention may promote wound healing.

CONCLUSIONS

In summary, novel DOXY formulations may be stable and biologically active tools amenable to complex wound care.

Penetration and efficacy of transdermal NSAIDs in a model of acute joint inflammation

Purpose

Prescription and OTC non-steroidal anti-inflammatory drugs (NSAIDs) are ubiquitous treatments for pain and inflammation; however, oral administration of these drugs may produce gastrointestinal (GI) side effects. Transdermal (TD) administration of NSAIDs circumvents these adverse events by avoiding the GI tract and, presumably, achieves regional drug levels of therapeutic effect and thereby, fewer off-target complications.

Methods

A drug quantification method was developed for ibuprofen and celecoxib in canine plasma and synovial fluid using liquid chromatography and mass spectrometry. This method was employed to evaluate the penetrance of ibuprofen and celecoxib topical formulations in dogs. Effectiveness of these topical NSAID formulations was compared to the equivalent oral drug concentration in a canine sodium-urate model of acute joint inflammation. In this model, pain was quantified using a modified Canine Brief Pain Inventory questionnaire and regional inflammation using joint caliper measurements; the significance of intervention was evaluated using linear mixed models for repeated measures along with Bonferroni corrections.

Results

After seven days of chronic topical administration, Delivra™ (DEL) formulations of ibuprofen and celecoxib generated serum levels of 2.9µg/mL and 220ng/mL and synovial fluid levels of 1.8 µg/mL and 203 ng/mL (respectively). In the canine model of acute inflammation, the overall treatment effects as well as the treatment by time interactions were strongly significant (P<0.001) for both drugs. Oral ibuprofen proved uniquely effective at the earliest time point, while all ibuprofen formulations were effective at treating pain at 8.5 and 24.5 hours post-induction. Similarly, all celecoxib formulations (oral and topical) were equally effective at 8.5 and 24.5 hours post-induction.

Conclusion

DEL formulations of ibuprofen and celecoxib successfully introduced these NSAIDs into synovial fluid at concentrations similar to those observed in circulation. Furthermore, these formulations reduced symptoms of pain associated with acute inflammation. Oral and transdermally delivered NSAIDs have similar pain relief effects; therefore, a replacement or combinatorial treatment may provide a more stable pain relief profile. In conclusion, this work supports further investigation of TD products in the treatment of regional inflammatory events.

Human blood analysis reveals differences in gene expression of catecholamine-regulated protein 40 (CRP40) in schizophrenia

Heat shock proteins (HSPs) are important players in neurodegeneration and psychiatric disorders. We previously reported significant reductions of a 40-kDa Catecholamine Regulated Protein (CRP40) in schizophrenia post-mortem brain specimens. This study investigated whether gene expression of CRP40 is altered in living subjects with schizophrenia. CRP40 mRNA was analyzed in white blood cells of first episode and chronic/treated schizophrenia subjects compared to healthy controls. Significant reductions in CRP40 mRNA were found among first episode schizophrenia subjects and chronic schizophrenia subjects compared to healthy controls (p<0.05 for both). These results suggest a possible functional role of CRP40 in the pathogenesis of schizophrenia.

Knockdown of mortalin within the medial prefrontal cortex impairs normal sensorimotor gating

The 70-kDa mitochondrial heat shock protein, mortalin, is a ubiquitously expressed, multifunctional protein that is capable of binding the neurotransmitter, dopamine, within the brain. Dopamine dysregulation has been implicated in many of the abnormal neurological behaviors. Although studies have indicated that mortalin is differentially regulated in response to dopaminergic modulation, research has yet to elucidate the role of mortalin in the regulation of dopaminergic activity. This study seeks to investigate the role of mortalin in the regulation of dopamine-dependent behavior, specifically as it pertains to schizophrenia (SCZ). Mortalin expression was knocked down through the infusion of antisense oligodeoxynucleotide molecules into the medial prefrontal cortex (mPFC). Rats infused with mortalin antisense oligodeoxynucleotide molecules exhibited significant prepulse inhibition deficits, suggestive of defects in normal sensorimotor gating. Furthermore, mortalin misexpression within the mPFC was coupled to a significant increase in mortalin protein expression within the nucleus accumbens at the molecular level. These findings demonstrate that mortalin plays an essential role in the regulation of dopamine-dependent behavior and plays an even greater role in the pathogenesis of SCZ.

Translocation of AIF in the human and rat striatum following protracted haloperidol, but not clozapine treatment

Loss of mitochondrial membrane integrity and consequent release of apoptogenic factors may be involved in mediating striatal neurodegeneration after prolonged treatment with the typical antipsychotic drug haloperidol. Apoptosis-inducing factor (AIF), an intramitochondrial protein, may have a large influence on mediating haloperidol-induced striatal neuron destruction. Translocation of this protein from mitochondria to the nucleus promotes cell death independently of the caspase cascade. To examine how AIF may contribute to haloperidol-induced apoptosis, AIF translocation was observed in three haloperidol treatment paradigms. SH-SY5Y cells were treated with both haloperidol and clozapine and examined for AIF immunofluorescence. Immunohistochemistry was also performed on human striatal sections obtained from the Stanley Foundation Neuropathology Consortium and on rat brain sections following 28 days of antipsychotic drug treatment. In the cellular model haloperidol, but not clozapine treatment increased the nuclear AIF immunofluorescent signal and decreased cell viability. Corollary to these findings, striatal sections from patients who had taken haloperidol and rats who were administered haloperidol both had an elevated nuclear AIF signal. The results provide novel evidence implicating the involvement of AIF in haloperidol-associated apoptosis and its relevance to the development of typical antipsychotic drug-related adverse effects such as tardive dyskinesia.

Decreased expression of a 40-kDa catecholamine-regulated protein in the ventral striatum of schizophrenic brain specimens from the Stanley Foundation Neuropathology Consortium

The majority of heat shock proteins (HSP) act as molecular chaperones protecting cells from deleterious stress. These proteins are able to inhibit the aggregation of partially denatured proteins and refold them into the correct conformation. They have also been shown to be involved in the pathogenesis of many neurodegenerative and psychiatric disorders. Previous reports from our laboratory have described a 40-kDa catecholamine-regulated heat-shock-like protein (CRP40). This study investigates CRP40 expression in ventral striatal specimens obtained from the Stanley Foundation Neuropathology Consortium (SFNC). CRP40 levels were significantly reduced in schizophrenic patients relative to the control group. However, ventral striatal samples of individuals diagnosed with major depression or bipolar disorder did not show significant changes in the expression of the protein. No differences in CRP40 levels were observed due to age, sex or postmortem interval (PMI). Further analysis of the schizophrenic group revealed that unmedicated and medicated patients showed decreases in ventral striatal CRP40 levels relative to the control group. However, the largest reduction in these levels was seen in unmedicated schizophrenic patients. In addition, relative to the unmedicated individuals, the clozapine- and haloperidol-treated groups showed elevations in ventral striatal CRP40 expression, although not significant. An increase in sample size may clarify this observation. Taken together, these results suggest a functional role of CRP40 in the pathogenesis of schizophrenia.