Activation of a novel α2AAR-spinophilin-cofilin axis determines the effect of α2 adrenergic drugs on fear memory reconsolidation.

Posttraumatic stress disorder (PTSD) after the pandemic has emerged as a major neuropsychiatric component of post-acute COVID-19 syndrome, yet the current pharmacotherapy for PTSD is limited. The use of adrenergic drugs to treat PTSD has been suggested; however, it is hindered by conflicting clinical results and a lack of mechanistic understanding of drug actions. Our studies, using both genetically modified mice and human induced pluripotent stem cell-derived neurons, reveal a novel α2A adrenergic receptor (α2AAR)-spinophilin-cofilin axis in the hippocampus that is critical for regulation of contextual fear memory reconsolidation. In addition, we have found that two α2 ligands, clonidine and guanfacine, exhibit differential abilities in activating this signaling axis to disrupt fear memory reconsolidation. Stimulation of α2AAR with clonidine, but not guanfacine, promotes the interaction of the actin binding protein cofilin with the receptor and with the dendritic spine scaffolding protein spinophilin to induce cofilin activation at the synapse. Spinophilin-dependent regulation of cofilin is required for clonidine-induced disruption of contextual fear memory reconsolidation. Our results inform the interpretation of differential clinical observations of these two drugs on PTSD and suggest that clonidine could provide immediate treatment for PTSD symptoms related to the current pandemic. Furthermore, our study indicates that modulation of dendritic spine morphology may represent an effective strategy for the development of new pharmacotherapies for PTSD.

Additive toxic effect of deltamethrin and cadmium on hepatic, hematological, and immunological parameters in mice.

Exposure to natural and man-made environmental toxins concurrently can pose a greater threat to multiple organs. In the present work, we investigated interactions between deltamethrin (DM) and cadmium (Cd), whose mechanisms of action in humans are poorly understood. Albino mice were randomly divided into four groups, each containing six mice: saline as control, DM-treated, cadmium chloride (CdCl2)-treated, and CdCl2 plus DM treated. After 2 weeks of treatment biochemical and hematological effects, total leukocyte count (TLC), differential leukocyte count, humoral-mediated immune responses, and histopathological studies were conducted. Mice exposed to DM and Cd showed a significant increase in aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Also, DM and Cd administration resulted in suppression of humoral immunity, erythrocyte count, hemoglobin, hematocrit, and TLC. Histopathological evidence revealed hepatic damage, supporting the AST and ALT findings. Cd and DM exhibited an additive type of toxicity. It could be concluded that these toxins either target different cellular pathways, or the individual amounts used in this study were not enough to saturate the toxicological target, thus producing additive effects.

Monoamine alterations in Alzheimer's disease and their implications in comorbid neuropsychiatric symptoms.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by relentless cognitive decline and the emergence of profoundly disruptive neuropsychiatric symptoms. As the disease progresses, it unveils a formidable array of neuropsychiatric manifestations, including debilitating depression, anxiety, agitation, and distressing episodes of psychosis. The intricate web of the monoaminergic system, governed by serotonin, dopamine, and norepinephrine, significantly influences our mood, cognition, and behavior. Emerging evidence suggests that dysregulation and degeneration of this system occur early in AD, leading to notable alterations in these critical neurotransmitters' levels, metabolism, and receptor function. However, how the degeneration of monoaminergic neurons and subsequent compensatory changes contribute to the presentation of neuropsychiatric symptoms observed in Alzheimer's disease remains elusive. This review synthesizes current findings on monoamine alterations in AD and explores how these changes contribute to the neuropsychiatric symptomatology of the disease. By elucidating the biological underpinnings of AD-related psychiatric symptoms, we aim to underscore the complexity and inform innovative approaches for treating neuropsychiatric symptoms in AD.

Androgen deprivation therapy exacerbates Alzheimer's-associated cognitive decline via increased brain immune cell infiltration.

Androgen deprivation therapy (ADT) for prostate cancer is associated with an increased risk of dementia, including Alzheimer's disease (AD). The mechanistic connection between ADT and AD-related cognitive impairment in patients with prostate cancer remains elusive. We established a clinically relevant prostate cancer-bearing AD mouse model to explore this. Both tumor-bearing and ADT induce complex changes in immune and inflammatory responses in peripheral blood and in the brain. ADT disrupts the integrity of the blood-brain barrier (BBB) and promotes immune cell infiltration into the brain, enhancing neuroinflammation and gliosis without affecting the amyloid plaque load. Moreover, treatment with natalizumab, an FDA-approved drug targeting peripheral immune cell infiltration, reduces neuroinflammation and improves cognitive function in this model. Our study uncovers an inflammatory mechanism, extending beyond amyloid pathology, that underlies ADT-exacerbated cognitive deficits, and suggests natalizumab as a potentially effective treatment in alleviating the detrimental effects of ADT on cognition.

Understanding neuropsychiatric symptoms in Alzheimer's disease: challenges and advances in diagnosis and treatment.

Neuropsychiatric symptoms (NPS) in Alzheimer's disease (AD) affect up to 97% of AD patients, with an estimated 80% of current AD patients experiencing these symptoms. Common AD-associated NPS include depression, anxiety, agitation, aggression, and apathy. The severity of NPS in AD is typically linked to the disease's progression and the extent of cognitive decline. Additionally, these symptoms are responsible for a significant increase in morbidity, mortality, caregiver burden, earlier nursing home placement, and greater healthcare expenditure. Despite their high prevalence and significant impact, there is a notable lack of clinical research on NPS in AD. In this article, we explore and analyze the prevalence, symptom manifestations, challenges in diagnosis, and treatment options of NPS associated with AD. Our literature review reveals that distinguishing and accurately diagnosing the NPS associated with AD remains a challenging task in clinical settings. It is often difficult to discern whether NPS are secondary to pathophysiological changes from AD or are comorbid psychiatric conditions. Furthermore, the availability of effective pharmaceutical interventions, as well as non-pharmacotherapies for NPS in AD, remains limited. By highlighting the advance and challenges in diagnosis and treatment of AD-associated NPS, we aspire to offer new insights into the complexity of identifying and treating these symptoms within the context of AD, and contribute to a deeper understanding of the multifaceted nature of NPS in AD.

A peptide blocking the ADORA1-neurabin interaction is anticonvulsant and inhibits epilepsy in an Alzheimer's model.

Epileptic seizures are common sequelae of stroke, acute brain injury, and chronic neurodegenerative diseases, including Alzheimer's disease (AD), and cannot be effectively controlled in approximately 40% of patients, necessitating the development of novel therapeutic agents. Activation of the A1 receptor (A1R) by endogenous adenosine is an intrinsic mechanism to self-terminate seizures and protect neurons from excitotoxicity. However, targeting A1R for neurological disorders has been hindered by side effects associated with its broad expression outside the nervous system. Here we aim to target the neural-specific A1R/neurabin/regulator of G protein signaling 4 (A1R/neurabin/RGS4) complex that dictates A1R signaling strength and response outcome in the brain. We developed a peptide that blocks the A1R-neurabin interaction to enhance A1R activity. Intracerebroventricular or i.n. administration of this peptide shows marked protection against kainate-induced seizures and neuronal death. Furthermore, in an AD mouse model with spontaneous seizures, nasal delivery of this blocking peptide reduces epileptic spike frequency. Significantly, the anticonvulsant and neuroprotective effects of this peptide are achieved through enhanced A1R function in response to endogenous adenosine in the brain, thus, avoiding side effects associated with A1R activation in peripheral tissues and organs. Our study informs potentially new anti-seizure therapy applicable to epilepsy and other neurological illness with comorbid seizures.

Cymbopogon schoenanthus (Ethkher) ameliorates cadmium induced toxicity in swiss albino mice.

Cadmium is among the toxic and hazardous metal widely dispersed in the environment in high levels. Current studies have provided new insights into antioxidant properties of bioflavonoid which have emerged as probable therapeutic and nutraceutical agents. The present study is geared to investigate the possible role of Cymbopogon schoenanthus (L.) Spreng. (or Ethkher) on heavy metal cadmium (Cd) induced oxidative stress in mice. Mice were randomly divided into four groups and treated for 15 days as follows: group 1: normal control-treated (saline); group 2: Ethkher leaves extract-treated (100 mg/kg); group 3: cadmium chloride (CdCl2) treated; group 4: CdCl2 plus Ethkher leaves extract. The results showed a significant reduction in hemoglobin, RBC and hematocrit in cadmium-treated mice as compared to control. Exposure to Cd caused a significant increase in the number of white blood cells (P < 0.05) indicating the occurrence of systemic inflammation. The results of this study also revealed that the mice intoxicated with Cd showed a significant increase in bilirubin, aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGTP) activities. Cd intoxication leads to suppression in humoral immunity. However, pretreatment with Ethkher extract reversed almost all the abnormalities in the blood parameters showing noteworthy protection against cadmium induced toxicity in mice. The outcome of the present study revealed that the Ethkher possessed significant immunomodulatory activity and had a preventive effect on the hematological alterations in Cd intoxicated mice.

Immunosuppressant drug tacrolimus induced mitochondrial nephrotoxicity, modified PCNA and Bcl-2 expression attenuated by Ocimum basilicum L. in CD1 mice.

Tacrolimus (TAC) is used sporadically as an immunosuppressive agent for organ transplantation, but its clinical used is limited due to its marked nephrotoxicity. Ocimum basilicum L. (Lamiaceae) (OB) had been shown to possess antioxidant, anti-inflammatory and nephroprotective activity, and effective at improving renal inflammation and glomerular. In our study, we aim to evaluate the efficacy of the OB against TAC-induced mitochondrial nephrotoxicity in CD1 mice. Mice were randomly divided into four groups. Group 1 (control group); administered orally with normal saline (1 mL/kg) for two weeks; Group 2 (OB extract treated-group) (500 mg/kg b.wt) gavaged once/day for two weeks; Group 3 (TAC-treated group) (3 mg/kg b.wt, administered ip once a day for two weeks); and Group 4; (TAC plus OB extract treated-group). Tacrolimus-induced nephrotoxicity was assessed biochemically and histopathologically. The OB extract was high in phenolic content (50.3 mg/g of gallic acid equivalent), total flavonoids (14.5 mg/g CE equivalent). The potential antioxidant efficacy of the extract (IC50) was 24.5 µg/mL. OB pretreatment significantly improved the TAC-induced changes in biochemical markers of nephrotoxicity for instance blood urea nitrogen (BUN), creatinine, total protein, and albumin (P < 0.01, when compared with TAC treated group). Also, it significantly restored the increase activities of TBARS, protein carbonyl (PC) (P < 0.001, when compared to healthy control group) and decreased activities of nonprotein thiol (NP-SH) levels, Mn-superoxide dismutase (Mn-SOD) and glutathione peroxidase (GPx) antioxidants of mitochondria. The nephroprotective efficacy of the OB leaves extract was further evident by histopathological analysis together with the PCNA-ir and Bcl2. The upshot of the present study revealed that the OB possessed significant antioxidant and nephroprotective activity and had a preventive effect on the biochemical alterations and histological changes in TAC-treated mice.

Stem Cell Applications for Treatment of Cancer and Autoimmune Diseases: Its Promises, Obstacles, and Future Perspectives.

Since the original discovery of stem cells, a new era of promising results has emerged in the clinical application of stem cells for the treatment of several important diseases, including cancer and autoimmune diseases. The plentiful research on stem cells during the past decades has provided significant information on the developmental, morphological, and physiological processes that govern tissue and organ formation, maintenance, and regeneration; cellular differentiation; molecular processes; and tissue homeostasis. In this review, we present the history of the use of stem cells in different clinical applications. Furthermore, we discuss the various therapeutic options for stem cells in cancer, followed by the role of stem cells in the treatment of autoimmune disorders. Additionally, we highlight the risks of and obstacles to the application of stem cells in clinical practice. Ultimately, we show future perspectives in stem cell use, with an aim to improve the clinical usefulness of stem cells.

Possible mechanism of adaptogenic activity of seabuckthorn (Hippophae rhamnoides) during exposure to cold, hypoxia and restraint (C-H-R) stress induced hypothermia and post stress recovery in rats.

The present study was carried out to investigate mechanism of adaptogenic activity of seabuckthorn dry leaves aqueous lyophilized extract, administered in rats at a dose of 100 mg/kg body weight prior to cold (5 degrees C)-hypoxia (428 mmHg)-restraint (C-H-R) exposure up to fall of T(rec) 23 degrees C and recovery (T(rec) 37 degrees C) from C-H-R induced hypothermia. The effect of extract treatment was studied on key metabolic regulatory enzymes in blood, liver and muscle and tissue glycogen in rats on attaining T(rec) 23 degrees C and post stress recovery of T(rec) 37 degrees C. In control rats during C-H-R exposure on attaining T(rec) 23 degrees C there was significant decrease in enzyme activities of blood hexokinase (HK), citrate synthase (CS) and glucose-6-phosphate dehydrogenase (G-6-PD); liver CS; and in muscle glycogen, and CS and G-6-PD activities. In control rats on recovery of T(rec) 37 degrees C there was also a significant decrease in liver and muscle glycogen levels along with decreased enzyme activities of blood G-6-PD; liver CS; and liver and muscle G-6-PD. This suggested that during severe stressful exposure to C-H-R and post stress recovery the aerobic metabolism as well as hexose monophosphate (HMP) pathway is suppressed. The single and five doses extract treatment restricted the decrease or better maintained tissue glycogen and enzyme activities, viz. HK, phosphofructokinase (PFK), CS and G-6-PD, in blood, liver and muscle, during C-H-R exposure (T(rec) 23 degrees C) and recovery of T(rec) 37 degrees C. The results suggest that seabuckthorn extract treatment caused a trend for shifting anaerobic metabolism to aerobic during C-H-R exposure and post stress recovery.

Modulatory effect of seabuckthorn leaf extract on oxidative stress parameters in rats during exposure to cold, hypoxia and restraint (C-H-R) stress and post stress recovery.

This study was carried out to examine the antioxidative potential, if any, of seabuckthorn leaf aqueous extract, administered orally in rats at a dose of 100 mg kg(-1) both in single and five doses, 30 min before cold (5 degrees C)-hypoxia (428 mm Hg)-restraint (C-H-R) exposure. The effect of the extract was studied on lipid peroxidation and antioxidant parameters in liver and gastrocnemius muscle of rats on attaining the rectal temperature (T(rec)) of 23 degrees C during C-H-R exposure and after recovery (T(rec)37 degrees C) from C-H-R-induced hypothermia. In untreated rats exposed to C-H-R, there was a significant increase in malondialdehyde (MDA) levels in liver and muscle along with decreased activity of catalase (CAT) and glutathione-S-transferase (GST) in liver and muscle. Single- and five-dose extract treatment restricted the increase in liver and muscle MDA levels and five doses of extract treatment further improved the levels of liver antioxidants, viz. reduced glutathione (GSH), on recovery of T(rec)37 degrees C, increased superoxide dismutase (SOD) during exposure and recovery, normalized CAT activity in liver during C-H-R exposure and an increase on recovery of T(rec)37 degrees C. The decreasing pattern of liver and muscle GST levels both in single-dose and five-dose extract treated rats was similar to that in untreated rats. Results suggested that supplementation with seabuckthorn extract helps to reduce oxidative stress in liver and muscle of rats during C-H-R exposure and post-stress recovery.

Ecological variations and role of heat shock protein in Artemisia judaica L. in response to temperature regimes of Tabuk, Saudi Arabia.

Artemisia judaica L. (Compositae) are shrubby herbs growing wildly in Tabuk region and distributed in the desert regions. This region is characterized by extremely variable environmental conditions where the temperature varies from extreme low to extreme high. These temperature regimes have a profound effect on morphology, growth physiology and biochemistry of the plants. The plant samples were collected from Tabuk-Jordan road (760 m above sea level) in the month of January, April, July and October 2013 to evaluate the effect of temperature dynamics on A. judaica L. in four different seasons. Physiological, biochemical alterations and heat shock proteins (HSPs) were studied during these seasons in order to evaluate the environmental adaptation and stress tolerance in response to temperature variations. Plant growth parameters showed a significant increase in height, fresh and dry matter accumulation, total chlorophyll, nitrogen, phosphorus, potassium, artemisinin and leaf relative water contents investigated in the month of April and October. Growth of plant was suppressed and an active role of carbonic anhydrase (CA), catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) was observed to cope with the extreme low temperature in January and extreme high temperature in July 2013. However, the plants collected in October and April did not show a statistical difference. Inductions in the expression of HSP90 were recorded in all the plants collected during April and October 2013 with no statistically significant difference. Therefore, based on the results it is recommended that during April and October the environmental conditions are best suitable for growth, development and medicinal use of Artemisia.

Recent incidence and descriptive epidemiological survey of breast cancer in Saudi Arabia.

OBJECTIVE: To review and analyze the pattern of breast cancer (BC) in the Kingdom of Saudi Arabia (KSA). METHODS: A retrospective review of BC among female patients was conducted at the Faculty of Sciences, Department of Biology, University of Tabuk, Tabuk, Saudi Arabia from January 1990 to December 2014. This report contains information obtained from the Saudi Cancer Registry and from King Faisal Specialist Hospital and Research Center. RESULTS: The number of women with BC increased steadily from 1990-2010. On the basis of the number of cases, the percentage distribution of BC appears to be increasing. There were 1152 female BC cases in 2008 in comparison with 1308 in 2009, and 1473 in 2010. Breast cancer ranked first among females accounting for 27.4% of all newly diagnosed female cancers (5378) in the year 2010. The average age at the diagnosis of BC was 48; weighted average was 49.8, and range 43-52. CONCLUSION: Among Saudi patients, there was a significant increase in the number of cases of BC, which occurs at an earlier age than in western countries. Continued vigilance, mammographic screening, and patient education are needed to establish early diagnosis and perform optimal treatment.

Phytochemical, antioxidant and mineral composition of hydroalcoholic extract of chicory (Cichorium intybus L.) leaves.

The phytochemical, antioxidant and mineral composition of hydroalcoholic extract of leaves of Cichorium intybus L., was determined. The leaves were found to possess comparatively higher values of total flavonoids, total phenolic acids. The phytochemical screening confirmed the presence of tannins, saponins, flavonoids, in the leaves of the plant. The leaf extract was found to show comparatively low value of IC50 for 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition. The IC50 value of chicory leaves extract was found to be 67.2 ± 2.6 µg/ml. The extracts were found to contain high amount of mineral elements especially Mg and Zn. Due to good phytochemical and antioxidant composition, C. intybus L., leaves would be an important candidate in pharmaceutical formulations and play an important role in improving the human health by participating in the antioxidant defense system against free radical generation.

Abrogation by Trifolium alexandrinum root extract on hepatotoxicity induced by acetaminophen in rats.

OBJECTIVE: Acetaminophen (APAP) is a substance that harms human health by stimulating free radical production. This study investigated the ability of Trifolium alexandrinum root (TAR) extract to reduce the hepatotoxicity induced by APAP in rats. METHODS: Animals were classified into four groups and treated for 6 weeks. Group 1: normal control-treated (saline); Group 2: TAR extract-treated (100 mg/kg); Group 3: APAP-treated; Group 4: APAP plus TAR extract. RESULTS: APAP significantly elevated AST (aspartate amino transferase), ALT (amino alanine transferase), ALP (alkaline phosphatase), GGTP (gamma glutamyl transpeptidase), bilirubin, and malondialdehyde with a significant decrease in glutathione, superoxide dismutase, glutathione peroxidase, catalase, and glutathione S-transferase compared with the control group. Administration of TAR extract combined with APAP improved the liver damage induced by APAP. Histopathological evidence, together with observed DNA fragmentation, supported the detrimental effect of APAP and the ameliorating effect of TAR extract on liver toxicity. CONCLUSION: TAR extract has beneficial properties and can reduce the liver damage and toxicity induced by APAP. DISCUSSION: Free radical mediated processes have been implicated in the pathogenesis of many diseases. The protective effect of TAR root extract on APAP-induced hepatotoxicity in rats appears to be related to inhibition of lipid peroxidation and enhancement of antioxidant enzyme levels, in addition to a free radical scavenging action.

Ameliorating effect of chicory (Chichorium intybus L.) fruit extract against 4-tert-octylphenol induced liver injury and oxidative stress in male rats.

The current study was carried out to elucidate the modulating effect of chicory (Cichorium intybus L.) fruit extract (CFR) against 4-tert-OP induced oxidative stress and hepatotoxicity in male rats. Rats were divided into four groups and treated for 8 weeks as follow: group 1: normal control-treated (saline); group 2: chicory fruit extract-treated (100 mg/kg); group 3: 4-tert-OP treated; group 4: 4-tert-OP plus chicory fruit extract. The obtained results revealed that rats which received 4-tert-OP showed a significant increase in liver TBARS and bilirubin, aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGTP) activities. While a significant decrease in the levels of GSH, SOD, catalase recorded. On the other hand, CFR extract succeeded to modulate these observed abnormalities resulting from 4-tert-OP as indicated by the reduction of TBARS and the pronounced improvement of the investigated biochemical and antioxidant parameters. Histopathological evidence, together with observed PCNA and DNA fragmentation, supported the detrimental effect of 4-tert-OP and the ameliorating effect of CFR extract on liver toxicity. So, it could be concluded that chicory has a promising role and it worth to be considered as a natural substance for ameliorating the oxidative stress and hepatic injury induced by 4-tert-OP compound.

Potential molecular mechanisms for decreased synaptic glutamate release in dysbindin-1 mutant mice.

Behavioral genetic studies of humans have associated variation in the DTNBP1 gene with schizophrenia and its cognitive deficit phenotypes. The protein encoded by DTNBP1, dysbindin-1, is expressed in forebrain neurons where it interacts with proteins mediating vesicular trafficking and exocytosis. It has been shown that loss of dysbindin-1 results in a decrease in glutamate release in the prefrontal cortex; however the mechanisms underlying this decrease are not fully understood. In order to investigate this question, we evaluated dysbindin-1 null mutant mice, using electrophysiological recordings of prefrontal cortical neurons, imaging studies of vesicles, calcium dynamics and Western blot measures of synaptic proteins and Ca(2+) channels. Dysbindin-1 null mice showed a decrease in the ready releasable pool of synaptic vesicles, decreases in quantal size, decreases in the probability of release and deficits in the rate of endo- and exocytosis compared with wild-type controls. Moreover, the dysbindin-1 null mice show decreases in the [Ca(2+)]i,expression of L- and N-type Ca(2+)channels and several proteins involved in synaptic vesicle trafficking and priming. Our results provide new insights into the mechanisms of action of dysbindin-1.

Optogenetically evoked gamma oscillations are disturbed by cocaine administration.

Drugs of abuse have enormous societal impact by degrading the cognitive abilities, emotional state and social behavior of addicted individuals. Among other events involved in the addiction cycle, the study of a single exposure to cocaine, and the contribution of the effects of that event to the continuous and further use of drugs of abuse are fundamental. Gamma oscillations are thought to be important neural correlates of cognitive processing in the prefrontal cortex (PFC) which include decision making, set shifting and working memory. It follows that cocaine exposure might modulate gamma oscillations, which could result in reduced cognitive ability. Parvalbumin-positive fast-spiking interneurons play an orchestrating role in gamma oscillation induction and it has been shown recently that gamma oscillations can be induced in an anesthetized animal using optogenetic techniques. We use a knock-in mouse model together with optogenetics and in vivo electrophysiology to study the effects of acute cocaine on PFC gamma oscillation as a step toward understanding the cortical changes that may underlie continuous use of stimulants. Our results show that acute cocaine administration increases entrainment of the gamma oscillation to the optogentically induced driving frequency. Our results also suggest that this modulation of gamma oscillations is driven trough activation of D1 receptors. The acute cocaine-mediated changes in mPFC may underlie the enhancement of attention and awareness commonly reported by cocaine users and may contribute to the further use and abuse of psychostimulants.

Lysosomal signaling enhances mitochondria-mediated photodynamic therapy in A431 cancer cells: role of iron.

In photodynamic therapy (PDT), light activates a photosensitizer added to a tissue, resulting in singlet oxygen formation and cell death. The photosensitizer phthalocyanine 4 (Pc 4) localizes primarily to mitochondrial membranes in cancer cells, resulting in mitochondria-mediated cell death. The aim of this study was to determine how lysosomes contribute to PDT-induced cell killing by mitochondria-targeted photosensitizers such as Pc 4. We monitored cell killing of A431 cells after Pc 4-PDT in the presence and absence of bafilomycin, an inhibitor of the vacuolar proton pump of lysosomes and endosomes. Bafilomycin was not toxic by itself, but greatly enhanced Pc 4-PDT-induced cell killing. To investigate whether iron loading of lysosomes affects bafilomycin-induced killing, cells were incubated with ammonium ferric citrate (30 µM) for 30 h prior to PDT. Ammonium ferric citrate enhanced Pc 4 plus bafilomycin-induced cell killing without having toxicity by itself. Iron chelators (desferrioxamine and starch-desferrioxamine) and the inhibitor of the mitochondrial calcium (and ferrous iron) uniporter, Ru360, protected against Pc 4 plus bafilomycin toxicity. These results support the conclusion that chelatable iron stored in the lysosomes enhances the efficacy of bafilomycin-mediated PDT and that lysosomal disruption augments PDT with Pc 4.