Hanan M. El-Gowelli

Antibiotic-free nanotherapeutics: Hypericin nanoparticles thereof for improved in vitro and in vivo antimicrobial photodynamic therapy and wound healing

Hypericin (HY) is a naturally-occurring, potent photosensitizer. However, its lipophilicity limits its therapeutic applications. Our attempt is, thus, to develop a biodegradable nanocarrier for hypericin capable of preserving its antibacterial photoactivity. Amphiphilic block copolymers were synthesized to prepare hypericin-laden nanoparticles (HY-NPs). The antimicrobial photoactivity of HY-NPs was assessed; in vitro against biofilm and planktonic cells of methicillin resistant Staphylococcus aureus (MRSA) clinical isolates and in vivo on infected wounds in rats. Nanoparticles of 45 nm in diameter ensured higher amounts of reactive oxygen species upon irradiation. HY-NPs demonstrated superior inhibition of biofilm over planktonic cells. In vivo wound healing studies in rats revealed faster healing, better epithelialization, keratinization and development of collagen fibers when HY-NPs were applied. Determination of growth factors and inflammatory mediators in the wound area confirmed superior healing potential of nanoencapsulated hypericin suggesting that hypericin can join the era of antibiotic-free antimicrobial therapy.

Bioburden-responsive antimicrobial PLGA ultrafine fibers for wound healing.

Despite innovation in the design and functionalization of polymer nanofiber wound healing materials, information on their interaction with the biochemical wound environment is lacking. In an earlier study, we have reported the interaction of fusidic acid-loaded PLGA ultrafine fibers (UFs) with wound bacteria. Massive bacterial colonization and the formation of a dense biofilm throughout the mat were demonstrated. This was associated with a marked enhancement of initial drug release at concentrations allowing eradication of planktonic bacteria and considerable suppression of biofilm. The present study aimed at extending earlier findings to gain more mechanistic insights into the potential response of the fusidic acid-laden UFs under study to controlled microbial bioburden. Initial drug release enhancement was shown to involve surface erosion of the ultrafibrous mats likely mediated by microbial esterase activity determined in the study. Release data could be correlated with microbial bioburden over the inoculum size range 10³-10⁷ CFU/ml, suggesting a bioburden-triggered drug release enhancement mechanism. Moreover, the effectiveness of fusidic acid-laden UFs in the healing of either lightly contaminated or Staphylococcus aureus heavily infected wounds in a rat model suggested in-use relevant antimicrobial release patterns. Findings indicated active participation of polymer ultrafine wound dressings in a dynamic interaction with the wound milieu, which affects their structure-function relationship. Understanding such an interaction is fundamental to the characterization and performance assessment of wound materials under biorelevant conditions and the design of polymer-based infection-responsive biomaterials.

Short-term aortic barodenervation diminishes α1-adrenoceptor reactivity in rat aortic smooth muscle

Our previous studies have shown that aortic baroreceptor denervation elicits acute increases in blood pressure and significant elevations of sympathetic activity and peripheral vascular resistance. This study investigated the short-term (3 and 48 h) effect of aortic barodenervation and associated sympathetic hyperactivity on the functional activity of alpha 1-adrenoceptors in rat aortic smooth muscle. Compared with sham operation, aortic barodenervation caused acute rises in blood pressure and heart rate and reductions in baroreflex sensitivity. Blood pressure and heart rate remained elevated when measured in conscious aortic barodenervated rats 3 h after surgery but subsided to sham-operated levels at 48 h; the baroreflex sensitivity, however, remained attenuated. Hexamethonium (0.5-4 mg/kg, i.v.) elicited significantly (P < 0.05) greater depressor responses in conscious aortic barodenervated rats than in sham-operated rats at both 3 and 48 h, suggesting a higher sympathetic activity in denervated rats. Exposure of aortic rings from aortic barodenervated and sham-operated rats to cumulative addition of phenylephrine (alpha 1-adrenoceptor agonist, 3 x 10(-8)-1 x 10(-4) M) resulted in concentration related contractile responses that were similar in the two groups of rats at 3 h in contrast to significantly (P < 0.05) smaller contractions in rings from denervated rats at 48 h. The maximum contraction developed (Emax) at 48 h showed approximately 50% reduction in rings from aortic barodenervated compared with sham-operated rats (239 +/- 16 vs. 558 +/- 15 mg tension/mg tissue). The pA2 value for prazosin (alpha 1-adrenoceptor antagonist) was not altered by aortic barodenervation at 3 h but showed significant (P < 0.05) increases, compared with sham-operated values, at 48 h. It is concluded that short-term aortic barodenervation results in an elevation of sympathetic activity that coincides with reduced responsiveness of aortic smooth muscle to alpha 1-adrenoceptor activation. The aortic barodenervation-induced alpha 1-adrenoceptor desensitization is not a result of decreased receptor affinity but may involve an alteration of receptor density or in the post-receptor activation events.

Pioglitazone abrogates cyclosporine-evoked hypertension via rectifying abnormalities in vascular endothelial function

In addition to insulin sensitization, the thiazolidenedione drug pioglitazone exhibits favorable circulatory effects. Here, we hypothesized that pioglitazone protects against the hypertension and related vascular derangements caused by the immunosuppressant drug cyclosporine (CSA). Compared with vehicle (olive oil)-treated rats, chronic treatment with CSA (20mg/kg/day s.c., for 14 days) increased blood pressure (BP), reduced the aortic protein expression of phosphorylated eNOS (p-eNOS), and impaired responsiveness of isolated aortas to endothelium-dependent vasorelaxations induced by carbachol. The effects of CSA on BP, aortic p-eNOS, and carbachol relaxations were abolished upon concurrent administration of pioglitazone (2.5mg/kg/day). Serum levels of adiponectin, an adipose tissue-derived adipokine, were not altered by CSA but showed significant elevations in rats treated with pioglitazone or pioglitazone plus CSA. The possibility that alterations in the antioxidant and/or lipid profile contributed to the CSA-pioglitazone BP interaction was investigated. Pioglitazone abrogated the oxidative (aortic superoxide dismutase), lipid peroxidation (aortic malondialdyde), and dyslipidemic (serum LDL levels and LDL/HDL ratio) effects of CSA. Histologically, CSA caused focal disruption in the endothelial lining of the aorta and this effect disappeared in rats co-treated with pioglitazone. Collectively, pioglitazone abrogates the hypertensive effect of CSA via ameliorating detrimental changes in vascular endothelial NOS/NO pathway and oxidative and lipid profiles caused by CSA.

Montelukast abrogates rhabdomyolysis-induced acute renal failure via rectifying detrimental changes in antioxidant profile and systemic cytokines and apoptotic factors production.

In addition to antiasthmatic effect, the cysteinyl leukotriene receptor 1 (CysLT₁) antagonist montelukast shows renoprotective effect during ischemia/reperfusion and cyclosporine-induced renal damage. Here, we proposed that montelukast protects against rhabdomyolysis-induced acute renal failure. Compared with saline-treated rats, at 48 h following the induction of rhabdomyolysis using intramuscular glycerol (10 ml 50% glycerol/kg), significant elevations in serum levels of urea, creatinine, phosphate and acute renal tubular necrosis were observed. This was associated with elevations in serum Fas, interleukin-10, tumor necrotic factor-alpha, and transforming growth factor-beta1 and renal malondialdehyde and nitrite and detrimental reductions in renal catalase and superoxide dismutase activities. The effects of rhabdomyolysis on renal functional, biochemical and structural integrity and the associated changes in cytokines and Fas levels were abolished upon concurrent administration of montelukast (10 mg/kg i.p.) for 3 days (1 day before and 2 days after induction of rhabdomyolysis). Alternatively, administration of the anti-oxidant, α-tocopherol (400 mg/kg i.m.) for 3 days, succeeded in alleviating renal oxidative stress, but had no significant effect on the circulating levels of most cytokines and partially restored kidney functional and structural damage. Serum level of interleukin-6 was not altered by rhabdomyolysis but showed significant elevations in rats treated with montelukast or α-tocopherol. Collectively, motelukast abrogated functional and structural renal damage induced by rhabdomyolysis via ameliorating renal oxidative stress and modulation of systemic cytokines and apoptotic factors production. The results of this work are expected to open new avenues for early prevention of rhabdomyolysis-induced acute renal failure using selective CysLT₁ antagonists such as montelukast.

Celecoxib offsets the negative renal influences of cyclosporine via modulation of the TGF-β1/IL-2/COX-2/endothelin ETB receptor cascade

Endothelin (ET) signaling provokes nephrotoxicity induced by the immunosuppressant drug cyclosporine A (CSA). We tested the hypotheses that (i): celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, counterbalances renal derangements caused by CSA in rats and (ii) the COX-2/endothelin ET(B) receptor signaling mediates the CSA-celecoxib interaction. Ten-day treatment with CSA (20 mg/kg/day) significantly increased biochemical indices of renal function (serum urea, creatinine), inflammation (interleukin-2, IL-2) and fibrosis (transforming growth factor-β₁, TGF-β₁). Histologically, CSA caused renal tubular atrophy along with interstitial fibrosis. These detrimental renal effects of CSA were largely reduced in rats treated concurrently with celecoxib (10 mg/kg/day). We also report that cortical glomerular and medullary tubular protein expressions of COX-2 and ET(B) receptors were reduced by CSA and restored to near-control values in rats treated simultaneously with celecoxib. The importance of ET(B) receptors in renal control and in the CSA-celecoxib interaction was further verified by the findings (i) most of the adverse biochemical, inflammatory, and histopathological profiles of CSA were replicated in rats treated with the endothelin ETB receptor antagonist BQ788 (0.1 mg/kg/day, 10 days), and (ii) the BQ788 effects, like those of CSA, were alleviated in rats treated concurrently with celecoxib. Together, the data suggest that the facilitation of the interplay between the TGF-β1/IL-2/COX-2 pathway and the endothelin ET(B) receptors constitutes the cellular mechanism by which celecoxib ameliorates the nephrotoxic manifestations of CSA in rats.

Enhanced endothelial nitric oxide activity contributes to the reduced responsiveness of vascular α1-adrenoceptors following aortic barodenervation

We have recently shown that short-term aortic barodenervation diminishes constrictor responses to activation of alpha1-adrenoceptors in rat aortic smooth muscle. This study investigated the potential role of vascular endothelium and its derived vasoactive substances, nitric oxide and prostaglandins, in the reduced alpha1-adrenoceptor responsiveness after aortic barodenervation. Exposure of isolated aortic rings from aortic barodenervated and sham-operated rats 48 h after surgery to cumulative addition of phenylephrine (alpha1-adrenoceptor agonist, 3 x 10(-8) - 1 X 10(-4) M) resulted in concentration-related contractions that were significantly (P < 0.05) smaller in rings of denervated rats. Removal of the endothelium increased phenylephrine-mediated contractions in rings obtained from aortic barodenervated rats to near sham-operated levels as demonstrated by the similar contractile responses and slopes of the regression lines of the concentration-response curves. Pretreatment with indomethacin (cyclooxygenase inhibitor, 1 x 10[-5] M) had no effect on contractile responses to phenylephrine in rings from both groups of rats. In contrast, N(G)-nitro-L-arginine (nitric oxide synthase inhibitor, 3 x 10[-5] M) elevated basal vascular tone and significantly (P < 0.05) increased alpha1-adrenoceptor responsiveness, effects that were more evident in rings from denervated compared with sham-operated rats. N(G)-nitro-L-arginine produced significantly (P < 0.05) greater increases in the slopes of the regression lines (136.1 +/- 22% vs. 73.0 +/- 8.6% mg tension/mg tissue/log molar concentration) and maximum contractile response (Emax) to phenylephrine (161.2 +/- 8.2% vs. 76.7 +/- 6.1%) in rings from denervated compared with sham-operated rats suggesting an enhanced nitric oxide activity in aortas of denervated rats. This notion is further supported by the finding that cumulative i.v. administration of N(G)-nitro-L-arginine (1, 2, 4 and 8 mg/kg) elicited significantly (P < 0.05) greater pressor responses in conscious barodenervated compared with sham-operated rats. These results suggest that the endothelium plays a major role in the reduced constrictor responses to alpha1-adrenoceptor activation that occurs shortly after aortic barodenervation. This effect of the endothelium appears to involve, at least in part, enhancement of endothelial nitric oxide activity.

Endothelin ETA receptor/lipid peroxides/COX-2/TGF-β1 signalling underlies aggravated nephrotoxicity caused by cyclosporine plus indomethacin in rats.

Cyclosporine (CSA) and non‐steroidal anti‐inflammatory drugs (NSAIDs) are co‐prescribed for some arthritic conditions. We tested the hypothesis that this combined regimen elicits exaggerated nephrotoxicity in rats via the up‐regulation of endothelin (ET) receptor signalling.

Central modulation of cyclosporine-induced hypertension

Arterial hypertension is a considerable side effect that accompanies the clinical use of immunosuppressant drugs such as cyclosporine (CSA). In addition to promoting graft rejection, uncontrolled hypertension is a major risk factor for atherosclerosis, left ventricular hypertrophy, heart failure, and premature death. Most, if not all, reports that reviewed the hypertensive effect of CSA and underlying mechanisms focused on the roles of peripheral vasoactive machinaries, perhaps because of the limited capacity of CSA to diffuse to brain tissues and the lack of any appreciable effect for centrally administered CSA on blood pressure (BP) or central sympathetic outflow. This review focuses primarily on evidence that supports a modulatory role for central neural pathways, as go-between afferent and efferent sympathetic circuits, in the elicitation of the hypertensive action of CSA. Other areas covered briefly in the review include (1) an outline of peripheral mechanisms that contribute to the hypertensive action of CSA, and (2) comparisons of the BP effects of CSA and other calcineurin-dependent (tacrolimus) and independent (sirolimus) immunosuppressants. The knowledge of these mechanisms, central and peripheral, may permit the identification of new therapeutic strategies against CSA hypertension.

Facilitation of central imidazoline I1‐site/extracellular signal‐regulated kinase/p38 mitogen‐activated protein kinase signalling mediates the hypotensive effect of ethanol in rats with acute renal failure

Background and purpose:  This study investigated the role of central sympathetic activity and related mitogen‐activated protein kinase (MAPK) signalling in the cardiovascular effects of ethanol in a model of acute renal failure (ARF).